Cyclic esters of calixarenes with phthalic acid and pyromellitic acid; synthesis and X-ray molecular structures

摘要

J. CHEM. SOC. PERKIN TRANS. 1 1994 Cyclic Esters of Calixarenes with Phthalic Acid and Pyromellitic Acid; Synthesis and X-Ray Molecular Structures Dagmar Kraft/' Volker Bohmer,*.a Walter Vogt,a George Ferguson *JJ and John F. Gallagherb a Institute for Organic Chemistry, J.-J.-Becher Weg 34 SB7, Johannes Gutenberg University, D-55099Mainz, Germany Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, Canada, N7 G 2W 7 The reaction of phthaloyl dichloride with tert-butylcalix[4] -, calix[5] -and calix[6] -arene has been studied. While the 1.2-bridged macrocyclic ester is the main product in the case of calix[4]- and calix[6] -arene, the intramolecular bridging of the calix[5]arene occurs mainly in the 1.3-position. The derivatives of calix[4]- and calix[6]-arene could be further 0-alkylated and the ester bonds may be easily hydrolysed in these derivatives.1.2-Singly bridged derivatives of calix[4] -and calix[6] -arene were also obtained with CICH,Br. Reaction of tert- butylcalix[4]arene with pyromellitic acid tetrachloride leads to the formation of a new double calixarene. The structures of two cyclic esters have been determined by X-ray crystallography. Crystals of compound 600.2 MeOH are triclinic, space group Pi, with two molecules in a unit cell of dimensions a = 10.9292(6), b = 15.0534(10), c = 16.8534(14) A, a = 94.195(6)", /I= 90.044(6)", y = 100.171(5)". R = 0.075 for 21 87 observed reflections. Crystals of compound 800.83 C,H,-0.38 C,H,, are monoclinic, space group P2,/n, with 4 molecules in a unit cell of dimensions a = 14.5554(13), b = 35.3802(24), c = 15.01 60(12) A, p = 99.782(7)", R = 0.072 for 4028 observed reflections.The phthaloyl residue is enclathrated in the molecular cavity of a neighbouring calix[6]arene in a self-inclusion process interactions. The rapid progress in calixarene chemistry has led not only to a huge variety of derivatives in which all hydroxy groups or all para-positions are substituted in the same way, but also to an increasing number of compounds in which only some of these groups have reacted. Selective functionalization of calix[4]- arenesl leading (in a more or less rational way) to single regioisomers or stereoisomers (conformational isomers) has been described for many different examples.To mention but a few the synthesis of all possible conformational isomers of tetrakisbutyl ethers,2 the preparation of chiral tri-0-alkylated calixC4larenes or the construction of new, sophisticated chromoionophors may be taken to illustrate the possibilities. A similar development has started now in the calixC6larene series. Various partially 0-alkylated '-'and 0-acylated lo derivatives have been obtained in a more or less selective manner, including cyclic ethers 11*12 and cyclic Very recently all possible methyl ethers of tert-butylcalix[6]arene have been described. l4The situation with calixC5larenes as well as with higher homologues is not yet as well explored. Recently we have prepared 1,3-crown ether derivatives" of tert-butylcalixC5larene which represent the first examples of selectively 0-alkylated calixC5)arenes.Several 1,3,5,7-tetrakis- benzyl ethers of calix[8]arenes have been also described.17 While most bifunctional reagents lead to the connection of two opposite phenolic oxygens in calix[4]arenes if intra- molecular bridging occurs at all,? we could show that phthaloyl dichloride 2 forms the intrabridged 1,Zdiester 3 in reasonable yield.23 We therefore concluded that the phthaloyl residue might be developed in general into a suitable protective group for two adjacent OH groups in calixarenes, since it should be possible to hydrolyse these ester groups again, after further t 1,2-Bridging was observed in addition to the formation of a double calixarene via the 1,3-positions of tert-butylcalix[4]arene with o-bisbromomethylated benzene (see ref.21), and recently 1,2-bridging with CICH,Br was described by Pappalardo and co-workers (see ref. 22). resulting from C-H n(arene) hydrogen-bonding alkylation of the remaining OH groups. Although this hope has not yet been entirely fulfilled, some interesting results emerged from this idea. It should be mentioned that 1,Zdiethers have been synthesized either by direct alkylation in the presence of a strong base (NaH) or by selective cleavage of adjacent methoxy groups in the tetrakismethyl ether.24*25 Results and Discussion Cyclic Esters of Phthalic Acid and tert-Butylcalix[4]arene.-Reaction of tert-butylcalix[4]arene la with phthaloyl di-chloride 2 in tetrahydrofuran (THF) in the presence of potassium tert-butoxide gave compound 3 in 30% yield while 26% of the original tetraol la could be recovered (as formerly described)23 (Scheme 1).An increase of the concentrations to enforce a more complete conversion led, however, to a decrease in yield. CsF in acetonitrile, a reaction medium used to obtain the doubly intrabridged derivative 4 also gave lower yields of compound 3. A slight increase in the yield of compound 3 to 34% was obtained with sodium hydride in THF under conditions where compound la (6.5 g) was allowed to react in THF (250 cm3). Thus, although compound 3 can be isolated only by flash chromatography it represents an easily accessible starting material for further derivatization, since it may be obtained without special dilution conditions.We have studied in some detail the further alkylation of diol 3 with ethyl bromoacetate 5. Reaction of compound 3 with excess of ester 5 (4-6 molar) in acetonitrile with K2C03 or CsF as base gave the monoalkylated product 6a in 37-39% yield (isolated by flash chromatography) (Scheme 2). NaH in THF led to a slightly higher yield (43%) of this compound, while still no dialkylated product was isolable. However, reaction of diol3 with ester 5 (4 mol equiv.) in THF-dimethylformamide (DMF) (50:50) in the presence of Cs,C03 gave the two products 6b and 6c in 23 and 45% yield, respectively, which by 'H NMR and mass spectroscopic evidence are both di-0-alkylated.+ Cocl la n=4 2 (lb n =5) (Icn =6) I --0 3 (34%) 4 (18%) Scheme 1 o=d '4=0 OW 5 1ii OR 6a (43%) 6b (23%) 6c (45%) Scheme 2 Reagents: i, NaH, THF; ii, Cs,CO,, THF-DMF Product 6b shows two singlets for the tert-butyl protons and one pair of doublets for the diastereotopic protons of the OCH,CO groups, which (inter alia) characterize it as a symmetrical product. This compound, in principle, could be in either the cone or the 1,2-alternate conformation. Owing to the fact that all three pairs of doublets (proportions 1 :2: 1) for the ArCH,Ar groups (especially that with double intensity atd 4.78 and 3.39 are found in the usual range, the cone conformation is most probable. For a 1,2-alternate conformation the environment for the two protons of the two CH, groups between ester and ether units would be more similar (although in principle different).Compound 6c shows four singlets for the tert-butyl groups, two pairs of doublets for the diastereotopic protons of two different OCH,CO groups and three pairs of doublets together with a (pseudo) singlet for the ArCH,Ar. This shows that this stereoisomer is fixed in the partial cone J. CHEM. soc. PERKIN TRANS. 1 1994 conformation. An independent and unambiguous confirmation was obtained in this case by X-ray analysis (see later). Owing to its conformation compound 6c is asymmetric and consequently chiral, while isomer 6b has a symmetry plane. Molecular asymmetry (due to the substitution pattern, and independent of the conformation) is also found in the monoalkylated compound 6a, demonstrated for instance by four signals for the tert-butyl groups.Four pairs of doublets for the ArCH,Ar protons in the usual range (S 4.45, 4.33, 4.15, 4.02, 3.51, 3.50, 3.39 and 3.26) suggest that a syn arrangement of the 0-alkyl residue and a cone conformation are highly probable. It should be emphasized that the doublet observed for the diastereotopic OCH,CO protons here as well as in the other cases has nothing to do with restricted rotation of this residue. De Mendoza and co-workers showed that the 13C NMR signals of carbon atoms belonging to methylene bridges which are situated between two phenol rings of different (anti) orientations are found at Sc 37-38, while those of methylene bridges between phenol rings of similar ((syn) orientations usually appear at dc 31-32.26 In the 13C NMR spectrum of compound 6b we find four signals in this region (Sc 30-40): 32.5, 33.9,34.3 and 35.1 ppm, none of them pointing to a 1,2-alternate conformation.On the other hand seven signals, at Sc 32. I, 33.9, 34.2, 34.4, 34.9, 38.9 and 39.1, are found in the spectrum of compound 6c, two of them (in agreement with Mendoza's observation) corresponding to the carbon atoms of the methylene bridge between the anti orientated phenol rings. Hydrolysis of all ester groups in compounds 6a-c was easily achieved by heating them with KOH in aq. methanol. Thus, the monoacid and two isomeric diacids were obtained.As in similar cases, these acids show 'H NMR spectra with very broad signals, which were not useful for their characterization. The compounds were identified by the molecular ion in their FD-mass spectra, and in the case of the monoacid also via the 'H NMR and 13C NMR spectra of the ethyl ester, which showed, for instance, three signals for tert-butyl groups (proportions 1 :2: 1) and two pairs of doublets for the two different ArCH,Ar protons. That two different diacids are obtained from compounds 6b and 6c,with a stable syn or anti arrangement of the OCH,CO,H groups, could be demon-strated by their different R,values on TLC. Cyclic Esters of Phthalic Acid and tert-Butylcalix[5]- and tert-Butylcalix[6]-arene.-When phthaloyl dichloride 2 was treated with the larger members of the calixarene family we always obtained product mixtures which were difficult to separate. In the case of the tert-butylcalix[5]arene lb the only pure product which up to now could be isolated by flash chromatography (14%) was a singly bridged cyclic ester 7.This was easily demonstrated by FD-mass spectrometry, while its 'H NMR spectrum showed the following surprising result: there are three singlets for OH groups (68.78,8.57 and 6.77), five pairs of doublets for the methylene bridges and five singlets for the tert-butyl groups (d 1.38, 1.30, 1.24, 1.14 and 1.11). For the aromatic protons of the tert-butylphenol units 9 (pseudo) singlets are discernible, one of them (S 7.26) arising from two protons.This means that the phthaloyl bridge obviously enforces a rigid (on the NMR timescale) and asymmetric conformation at room temperature. This is a rather unexpected result since both possible macrocyclic esters (proximal or 1,2- bridged and distal or 1,3-bridged) should have a symmetry plane intersecting the phthaloyl residue as was found for the 1,2- bridged calixC4larene 3 and also for 1,2- and 1,3-crown ether derivatives of compound lb." The entire lack of a symmetry element means that the molecule must be chiral, which was further confirmed by the doubling of some peaks in the presence of Pirkle's reagent. The rigid structure, on the other hand, may be the reason for the low yield. At 120 "C (C2D2Cl,) the 'H J.CHEM. soc. PERKIN TRANS. 1 1994 NMR spectrum of compound 7 shows the expected pattern of a symmetrical compound: two broad singlets for the OH groups (ratio 2 : I), two pairs of doublets (ratio 2: 3, because two AX systems are superimposed) for the three different methylene bridges, and three singlets for the tert-butyl groups (2 :2 : 1). O\'C I \ ?? 7 8 As pointed out elsewhere,' there is no entirely unambiguous way to distinguish between 1,2- or 1,3-disubstituted calixC51- arenes just on the basis of the number of signals in the NMR spectrum, as is easily done in the calixC4larene series. That one OH signal is found at 6 6.77 suggests, however, that this hydroxy group is isolated (no OH 9 OH hydrogen bond) from the other two which appear at lower field (S8.78 and 8.57).Therefore compound 7 should be the 1,3-bridged cyclic ester. In the case of tert-butylcalixC6larene lc a singly bridged ester 8 was isolated in 45% yield by flash chromatography, a yield even higher than that obtained with compound la. Again, five singlets for the six tert-butyl groups (1.42, 1.39, 1.36 (2 x But), 1.33 and 1.17) are found in the 'H NMR spectrum at room temperature, confirming the absence of a symmetry plane in the molecule, a conclusion which may be drawn also from the other signals (ArH, ArCH,Ar) although not in such a clear way. For the OH protons a broad singlet at 6 9.96 (2 H) and two singlets at 6 8.44 and 8.22 are found, which is interpreted in terms of a continuous row of intramolecularly hydrogen- bonded OH groups.Hence, two adjacent phenolic residues are bridged by the phthaloyl group, a result which was confirmed by the X-ray analysis of this compound. As in the case of compound 7 the 'H NMR spectrum measured at high temperature (1 20 "C; C,D,Cl,) shows the pattern of the symmetrical compound: two singlets for the OH groups (2: 2), four pairs of doublets (1 :2 :2 : 1) for the methylene bridges, and three singlets for the tert-butyl groups (2 : 2 : 2). When compound 8 was treated with an excess of ethyl bromoacetate 5 a complex reaction mixture was again obtained, from which a product could be isolated (40% yield) which, according to its FD-mass spectrum, must be a di-O-alkylated derivative of compound 8.The 'H NMR spectra recorded at various temperatures show very broad signals. Therefore, a structure can be assigned only tentatively, where the two OH groups opposite the phthaloyl bridge are alkylated. Further Macrocyclic Derivatives.-Formation of the cyclic 1,2-ester3, obtained with phthaloyl dichloride, suggested that larger molecular assemblies might be obtainable if the dicarboxylic acid were to be replaced by the corresponding tetracarboxylic acid. In fact, if compound la was treated with pyromellitoyl tetrachloride 10 (benzene- 1,2,4,5-tetracarboxylic acid tetrachloride) under dilution conditions (THF, KOBu' ) the double calixarene 9 could be isolated in 29% yield by flash chromatography (Scheme 3). The 'H NMR spectrum of compound 9 is very similar to that of compound 3.Two singlets for the tert-butyl groups, 3 pairs of doublets (proportions 1 : 2 : 1) for the methylene bridges and two pairs of doublets for the aromatic protons show that both calixarene substructures OH OH &aHO \ OH/ la o=c c=ofl+-o=c c=o I\00 Ow-(+14 10 9a (29%) 9b Scheme3 Reagents: KOBu',THF are connected to the bridging acid in an analogous way in both compounds. However, according to these data compound 9 may assume a U-or a Z-shaped form (9a or 9b), and it is not possible to rule out either of these possibilities. The strongest difference in chemical shifts, observed between analogous signals of compounds 3 and 9, is for the equatorial ArCH,Ar proton found at the highest field (S 3.32 us.2.89) and this can be explained, in principle, by slight conformational differences in either of the two forms of compounds 9 in comparison with compound 3. Unfortunately, the second stereoisomer could not be isolated, nor have single crystals of compound 9 been available up to now. The recent publication of a doubly bridged calixC4larene and a triply bridged ~alixC6larene~~which were obtained by reaction of the corresponding tert-butylcalixarenes with excess of BrCH,Cl in DMF in the presence of Cs,CO, prompts us to mention two singly bridged compounds, lla and llb, derived from calixarenes la and lc, which we obtained under similar conditions using, however, a stoichiometric amount or a slight excess of the alkylating agent.This type of bridging was initially used by Cram et al.27 to transform resorcinol-derived calixC4larenes into rigid cavitands by 4 intramolecular OCH,O bridges between the 8 ex0 hydroxy groups. In the light of the present results the reaction of the endo hydroxy groups of phenol-derived calixarenes seems not to be so easy. 742PH 0 '0 lla llb We obtained compounds lla and llb in 12 and 15% yield by flash chromatography; however, the reaction conditions are clearly not optimized. According to its 'H NMR spectrum the calixC6larene derivative llb is a flexible molecule with an effective symmetry plane, showing, for instance, three singlets of equal intensity for tert-butyl groups and a singlet and two pairs of doublets (proportions again 1 : 1 : 1) for the aromatic protons.Two singlets (ratio 1 :1) for the OH protons (S 9.11 and 7.83) may be taken as the most convincing proof for the presence of 1,2-bridging. The conformational situation is more complicated for com- pound lla. At room temperature the 'H NMR spectrum shows broad signals, while the low-temperature NMR spectra (-20 to -55 "C) gave sharper signals. Nevertheless, the assignment of 1224 J. CHEM. SOC. PERKIN TRANS. 1 1994 Table 1 The Q and x torsion-angle values (o)7 which define the conformation of the phthaloyl-bridged calixC4larene diester 6cZ8Comparison with the torsion angles of the tetraethers I 29 and I130 (partial cone conformations) and with the torsion angles of rn7p-octamethylcalix[4]arene HI 31 (cone conformation) OH R= CH2a OR OR I II m 6c I I1 m Molecule Q X v, X Q X v, X D-C +68 -91 +62 -102 +75 -81 +72 -109 C-B +9O -80 +97 -58 +80 -82 +112 -83 B-A +130 +129 +116 +116 +139 +139 +76 -105 A-D -128 -121 -117 -111 -142 -126 +lo9 -78 C( 16B) fl b(15D) Fig.1 A view of compound 6c-0.2MeOH with our labelling scheme. For clarity, the carbon and hydrogen atoms are drawn as small spheres of an arbitrary size. The oxygen atoms are depicted with their thermal parameters at the 35% probability level. Only one orientation of the disordered tert-butyl group on ring C is depicted these signals to a single conformation is not possible. At high temperature (90 "C; C,D,Cl,) the 'H NMR spectrum shows the expected pattern of a flexible molecule with a symmetry plane, namely two singlets for the tert-butyl groups, four singlets for the methylene bridges (proportions 1 :1:1 :2, one belonging to the ether bridge), one singlet for the OH groups, and two doublets and a pseudo-singlet for the eight aromatic protons.X-Ray Structure Analyses.-Although the crystals of com- pounds 6c and 8 diffracted relatively poorly (see Experimental section), we were able to obtain sufficient data to allow us to determine the details of their conformation unequivocally (Fig. 1). The conformation of compound 6c is defined by the angles which the aromatic rings make with the plane of the four methylene carbon atoms which link them, viz. -108.9(3)' (A), 112.6(3)' (B), 127.6(3)0 (C) and 100.7(3)0 (D) (interplanar angles 90" indicate that the aromatic ring system is tilted so that its tert-butyl group is directed away from the ring cavity; the negative angle indicates that the aryl grcup is inverted with respect to the other three aromatic systems). The aromatic rings A and C are at an interplanar angle of 19.0(3)" to one another but are orientated in opposite directions (the inverted ring A is pitched away from the methylene carbon plane, ring C is tilted well back from the calix cavity).The aromatic rings B and D are at an angle of 33.4(3)" to one another, both rings being tilted so that their tert-butyl groups are pitched away from the calix cavity. The molecular conformation of compound 6c can also be described by an approach recently proposed by Ugozzoli and Andreetti,28 using the torsion angles at the methylene carbon atoms, to which they assign the labels p and x.These torsion angles are listed in Table 1 and compared with the corresponding values of two tetraether derivatives [tetrakis- (pyridylmethyl) ether of calixC4larene I 29 and tetrakis(pyridy1- methyl) ether of tert-butylcalix[4]arene 1130] found also in the partial cone conformation. The sequence of the signs for v, and x, namely + -, + -, + +, --is characteristic of the partial cone conformation.28 A calixC4larene in the cone conform- ation, for instance, has the sequence + -, + -, + -, + -(see the example shown for comparison in Table 1).The 0 0 separations of the adjacent phenolic oxygens are 3.8 1(1),2.57(1), 3.05( 1) and 4.1 1(1) A in compound 6,while the diagonal 0 0 separations are 4.74(1) A [between O(1A) and O(1C) across the calixarene cavity] and 4.12( 1) A [between O(1B) and O(1D)]. The partial cone calix[4]arene 6c adopts a conformation in which the pendant CH,CO,Et group of the rotated aryl ring (A) is orientated awayfrom the calixarene cavity produced by the other three aryl rings and with its carbonyl oxygen exo to the calixarene cup. The open cup conformation thus adopted by compound 6c is suitable for a solvent molecule being enclathrated in the cavity, and this is what we observe. A partial occupancy methanol molecule is enclathrated in the molecular cavity.The O(M) O(1A) distance is 3.03 A and is consistent with 0-H .O hydrogen bonding between the hydroxy group of the methanol and the ethereal oxygen O(1A). We have previously reported calix[4]- arene structures which enclathrate small organic molecules within the molecular cavity, e.g. dichl~romethane,~~ ethanol 33 and a~etonitrile.~~ Although broadly similar, the partial cone conformation adopted by compound 6c differs from structures I and 11in the orientation of the aromatic rings (see the torsion angles in Table 1) and in the size of the calixarene cavity. This cavity can be considered to be intermediate in overall size between that observed in structure I (where the pyridyl group lies exo to the rather small cavity), and that described in structure 11(where the more open cavity is filled by the inverted pyridyl ring). The structures of the partial cone conformers of tert-butylbis- (cyanomethoxy)dimethoxycalix[4]arene and tert-butyldi-ethoxydimethoxycalix[4]arene 36 have also been recently reported, where the pendant group of the rotated aryl group lies J.CHEM. soc. PERKIN TRANS. 1 1994 1225 (O),Table 2 The v, and x torsion angle values which define the conformation of SZ8Comparison with the torsion angles of tetrakis(pyridylmethyl)calix[6]arene IV,8 hexakis(pyridylmethyl)calix[6]arene V 37 and tert-butylcalixC6larene VI 28*38 OR 1-OR OR OH OH bR OR ++ Iv V VI 8 Iv V VI Molecule Q, X v, X v, X Q, X €%A +115 -85 -11 +87 -49 -85 +91 -1OO A-F +lo3 -33 +99 -78 +37 -101 -95 +94 F-E +77 -97 +142 +I47 +I17 -7 +lo4 -84 E-D +53 -96 -11 +87 +49 +85 +86 -93 D-c +83 -93 4-99 -78 -37 +lo1 -95 +96 C-B -100 +82 +I42 +I47 -117 +7 +94 -94 c I0 Fig.2 An ORTEP view of the calixC6larene 8 with our labelling scheme; thermal ellipsoids and atom sizes are as in Fig. 1 outside the calix cavity, with a molecular conformation similar to that described in compound I.29 X-Ray analysis of the crystal of compound 8*0.83C7H8* 0.38C6H,, shows that the calix[6]arene adopts a very distorted cone-shaped conformation in the solid state which is primarily determined by the four intramolecular 0-H 0 hydrogen bonds and by the steric demands that the phthaloyl residue exerts on the aromatic rings (E) and (F) (Fig.2). The conformation of compound 8 can be defined by the angles which the aromatic rings make with the plane of four of the six methylene carbon atoms which are approximately coplanar, (C(7A), C(7B), C(7D), C(7E)), viz. 163(1)O (A), 131(1)O (B), 120(1)O (C), 165(1)O (D), 102(1)O (E) and 97(1)" (F) [interplanar angles 90" indicate that the aromatic ring system is tilted so that its tert-butyl group is directed backfrom the ring cavity; methylene carbon atoms C(7C) and C(7F) are not coplanar with the four-atom methylene carbon plane defined above]. Aromatic rings (A) and (D) are tiltedfar back from this plane and are close to being coplanar with the four-atom methylene carbon plane.Aromatic rings (B) and (C) are tilted well back from the plane whilst planes (E) and (F) are almost perpendicular to it. However, the molecular conformation of compound 8 is better and less ambiguously described by using the torsion angles Q and x. The Q-and X-values of compound 8 are listed in Table 2 and compared with the corresponding values for two other calixC6larene derivatives {the tetrakis(pyridylmethy1) ether of tert-butylcalix[6]arene IV and the hexakis(pyridy1- Fig. 3 A stereoview of the 'banana' shaped calixarene cavity in compound 8 with atoms depicted as their van der Waals spheres methyl) ether of tert-butylcalixC61arene V 37} and for tert- butylcalix[6]arene VI itself. For compound 8 the sequence of signs is + -, + -, + -, + -, + -, -+, which is not characteristic of ~alixC6larenes.~~ In fact no other example of a calixC6)arene or calix[6]arene derivative with this conforma- tion (indicated by the sequence of signs) has been found in the crystalline state to date.The tetraether IV lying on a two-fold crystallographic axis has the sequence + -, + +, -+, + -,+ + , -+,the hexaether V lying about an inversion centre has the sequence + -, + -, + +, -+, -+, --, and the parent tert-butylcalix[6]arene VI adopting a 'pinched cone' conformation with approximate two-fold symmetry has + -,+ -, -+, + -, + -, -+.Therangeofv,and~anglesand the sequence of signs indicate that the molecule has a very distorted conformation with an inversion occurring at the methylene carbon that links the B-c aromatic groups, showing that the macrocycle is formed by two subunits, which gives rise to two different sized compartments in the calix[6]arene.These v, and x angles are listed in Table 2 for comparison with the same torsion angles of tert-butylcalix[6)arene. The three O*.*O separations of the adjacent phenolic oxygens are 2.74(1), 2.64(1) and 2.64(1) A along the O(1D)- H O(1 C)-H O(1B)-H -O(1A) hydrogen-bonded chain. The corresponding H 0 distances are 1.77, 1SO and 1.84 A. These hydroxy-group hydrogens were clearly located from difference maps at an intermediate stage of the refinement. The phenolic oxygen O(1A) is involved in hydrogen bonding with the carbonyl oxygen 0(2F), the O(1A) O(2F) distance being 2.66(1) A, while the O(1A) O(1F) distance is 4.28(1) A.This carbonyl oxygen O(2F) is 0.87( 1) A removed from the eight-carbon-atom phthaloyl plane primarily resulting from the O-H*--O hydrogen bonding compared with the Fig. 4 An ORTEP view of enclathration of the phthaloyl residue of calixC6larene 8 within the molecular cavity of another. The arrows indicate the direction of the C-H interaction. Thermal ellipsoids and atom sizes are as in Fig. 1 ‘unperturbed’ carbonyl oxygen O(2E) which is -0.20( 1) A from the plane. The {0(1 F), C( 12F), 0(2F)] plane is at an angle of 74(1)” to the phthaloyl plane; 17(1)” is found for the corresponding (0(1 E), C( 12E), O(2E)) plane. The O(1D) O(2E) and O(1D) O(1E) distances are 5.10(1) and 3.54(1) A, which are not hydrogen-bonding distances, and the carbonyl oxygen O(2E) is exo to the calixC6larene cavity (Fig.3). The molecular cavity of the calixC6larene 8 is best described as having a ‘banana’ shaped conformation in the solid state as a result of the steric demands of the phthaloyl residue and the hydrogen-bonding process described above. The major compartment of this ‘curved’ cavity is filled by the phthaloyl residue of a neighbouring molecule related by an n-glide. This self-inclusion process with repetition along the n-glide direction produces a one-dimensional polymeric chain. The major driving forces in the enclathration of the phthaloyl residue in the calixC6larene molecular cavity are the favourable C-H n(arene) interactions that are formed (i) between the aromatic H(16E) of the phthaloyl group (C(13E) -C(18E)) and the aromatic ring {C(lD) C(6D)) and (ii) between the methyl group C(lOE1) of the disordered tert-butyl group attached to C(8E) and the phthaloyl group {C( 13E) C(18E)) (Fig.4). The hydrogen H(16E)-to-{C(lD) C(6D)) dis-tances are in the range 2.73-3.20 A, (C-H 0.95 A) with H(16E) orientated towards the aromatic ring D centroid and the C(lOEI)-to-{C(13E) C(18E)) distances are in the range 3.45-3.71 A. We have previously noted this effect in the structure of a calixC4larene guest/host complex, where the enclathrated CH,Cl, uses both C-H bonds to bind to two different arene rings.32 A disordered partiel occupancy toluene molecule partially fills the remaining calixC6larene niche and partial occupancy n-hexane molecules reside in the lattice disordered about inversion centres. J. CHEM. SOC. PERKIN TRANS. 1 1994 Perrin and Lecocq3’ have reported that two types of inclusion compounds have been found in calixarenes, with the guest either outside (as a solvate) or enclathrated within the calixarene cones (frequently described as cryptato-cavitate or tubulato/intercalato clathrates using the nomenclature pro- posed by Weber and Jose1 40). We have recently reported a third type of inclusion in calixarenes in the above mentioned calixC41- arene I1 where one of the aromatic rings is rotated so that its pyridine moiety is tightly accommodated inside the hydro- phobic cavity as a self-inclusion monomer.29 The present structure 8 (where the molecules are aligned in the lattice in the ac-plane as a one-dimensional molecular assembly) is best described as a self-inclusion polymer (Fig.4). We have seen this self-inclusion phenomenon previously in the structures of (i) a diester derivative of a calix[4]arene4’ and (ii) a ~alix[S]arene~~ but the present molecule 8 is a rare example of self-inclusion in a calix[6]arene. The structure of a 1,2,3-alternate tert-butylcalix[6]arene deri~ative,~~ where two of the ethereal chains partly fill the molecular cavity and the structure of dipropenyl~alix[4]arene,~’ where dimers are formed by mutual enclathration of the ally1 groups in the calixarene cavities.The major driving forces in these structures towards the formation of self-inclusion polymeric chains are the weaker C-H n(arene) hydrogen bonds. They often form after the other, more favourable hydrogen-bond donors and acceptors have combined in various ways. The resulting C-H n(arene) hydrogen bonds with a suitable pendant group either at the upper or lower rim of the calixCnlarene often dictate the overall packing arrangement. Experimenta1 M.p.s were determined with a Buchi melting point apparatus or with a MEL TEMP 2 capillary melting point apparatus and are uncorrected. ‘H NMR (200 MHz) and I3C NMR (50.3 MHz) spectra were recorded on a Bruker AC 200 or a Nicolet NT-200 WB spectrometer; ‘H NMR (400 MHz) and I3C NMR (100.6 MHz) spectra were recorded on a Bruker AM 400 spectrometer.J Values are given in Hz. EI mass spectra were recorded with a Varian MAT CH 7 A (70 eV), FAB mass spectra with a Finnigan MAT 90, and FD mass spectra with a Finnigan MAT 90 (5 kV/10 mA/min) spectrometer. Flash column chro-matography was performed on Merck silica gel 60 (230-400 mesh ASTM, 0.04-0.063 mm) with a N, pressure of 0.1-0.5 bar.* THF was dried over sodium-benzophenone and distilled freshly before use. Acetonitrile (p.a. quality) was dried over molecular sieves (4 A). CsF was heated for 1 h in Y~CUOat 100°C before use. All reactions were carried out under dry argon or nitrogen. Compound 3 was prepared as described in the literature23 except that NaH was used as a base.Pyromellitoyl tetrachloride 10 was prepared according to a method of Hodd and Shadbolt.43 5,11,17,23-Tetra-tert-butyl-25-[(ethoxycarbonyl)rnethoxy]-26-hydroxy-27,28-(phthaloyldioxy)calix[4]arene6a.-Ethyl bromoacetate 5(501 mg, 3 mmol) was added to a suspension of compound 3 (389.2 mg, 0.5 mmol) and NaH (95%; 50.5 mg, 2 mmol) in THF (50 cm3). The reaction mixture was refluxed for 15 h, then filtered, and the solvent was removed under reduced pressure. The solid residue was purified by flash-column chromatography (CH,Cl,) to give compound 6a as a solid (1 85 mg, 43%), m.p. 294-296 “C; 6,(200 MHz) 8.22 and 7.85 [2 x (1 H, dd, 3J 7.7 and 7.3, 4J 1.4, Phth Ar 2-and 2’-H)], 7.71 and * 1 bar = 10’ Pa.J. CHEM. SOC. PERKIN TRANS. 1 1994 7.62 [2 x (1 H, dt, 3J7.5, 1.7, Phth Ar 3- and 3'-H)], 7.31 (1 H, s, OH), 7.28, 7.25, 7.13, 7.12, 7.07, 6.98, 6.96 and 6.86 [8 x (1 H, d, 4J 2.2-2.3, ArH)], 4.64 (1 H, d, 'J 16.0, OCH,CO,), 4.45, 4.33, 4.15, 4.02, 3.51, 3.50, 3.39 and 3.26 [8 x (1 H, d, 'J 12.3-14.3, ArCH'Ar)], 4.124.01 (2 H, m, CH,Me), 3.99 (2 H, d, 'J 16.l,OCH,CO2), 1.25, 1.24, 1.17 and 1.14 [4 x (9 H, s, Bu')] and 1.22 (3 H, t, CH,Me); m/z (FD) 864.8 (M+. Calc. for C56H6408: M, 864.5). 5,11,17,23-Tetra-tert-butyl-25,26-bis[(ethoxycarbonyl)-methoxy]-27,2 8 -( phthalo y ldioxy) calix[4] arene 6b (Cone Isomer) and 6c (Partial Cone Isomer).-CszC03 (162.9 mg, 0.5 mmol) was added to a solution of compound 3 (194.6 mg, 0.25 mmol) in THF-DMF (30 cm3-30 cm3) and the mixture was stirred for 30 min at 50 "C.Then a solution of the dichloride 5 (1 67 mg, 1 mmol) in THF (10 cm3) was added dropwise and the mixture was refluxed for 16 h. After evaporation of the solvent the crude product was dissolved in CH,Cl, and washed with water. The organic phase was dried over MgS0, and the solvent was removed. Two spots on the TLC plate indicated the formation of two products, which were separated by flash- column chromatography (CHC1,diethyl ether, 20 : 1). Compound 6b: solid (55 mg, 23%); m.p. 19&191 "C; 6,(400 MHz) 7.96-7.94 (2 H, m, Phth Ar 2-H), 7.63-7.61 (2 H, m, Phth Ar 3-H), 7.24, 7.11, 6.94 and 6.86 [4 x (2 H, d, 1.7-2.3, ArH)], 4.78 and 3.39 [2 x (2 H, d, ,J 13.1, ArCH,Ar)], 4.38, 3.84,3.43and3.23[4 x (1 H,d,2J12.7-14.1,ArCH2Ar)],4.32 and 4.00 [2 x (2 H, d, 'J 16.1,OCHZCO)], 4.18 (4 H, q, 3J7.1, CH,Me), 1.27 (6 H, t, 7.2, CH,Me) and 1.25 and 1.07 [2 x (18 H, s, But)]; m/z (FD) 952.0 (M+.Calc. for C6,H7,0,,: M, 950.5). Compound 6c: solid (106 mg, 45%); m.p. 285-286°C; 6,(400 MHz) 7.80 and 7.74 [2 x (1 H, dd, 7.6, 1.2, Phth Ar 2-H)], 7.54 and 7.48 [2 x (1 H, dt, 7.5, 4J 1.4, Phth Ar 3-H)], 7.32, 7.08, 7.06 and 6.88 [4 x (1 H, d, ,J2.2- 2.4, ArH)], 7.16-7.15 (2 H, m, ArH), 6.97 (2 H, s, ArH), 4.88, 3.74, 3.44 and 3.38 [4 x (1 H, d, 'J 12.9-13.9, ArCH'Ar, syn)], 4.19-4.11 (2 H, m, CH,Me, syn), 4.02 (2 H, s, ArCH,Ar, anti), 4.01 and 3.78 [2 x (1 H, d, 'J 15.9 and 18.2, OCH,CO, syn)], 3.97 and 3.64 [2 x (1 H, d, 'J 15.4 and 16.1, ArCH'Ar, anti)], 3.54 (2 H, dq, 3J7.1, CH,Me, anti), 2.73 and 2.49 [2 x (1 H, d, ,J 15.8, OCH,CO, anti)], 1.30, 1.21, 1.15 and 1.10 [4 x (9 H, s, Bu')], 1.27 (3 H, t, 7.2, CH,Me, syn) and 0.69 (3 H, t, 3J7.1, CH,Me, anti); m/z (FD) 950.9 (M'.Calc. for C60H70010: M, 950.5). 5,llf17,23,29-Penta-tert-butyl-31,32,34-trihydroxy-33,35-(phthaloyldioxy)calix[5]arene7.-A mixture of compound 1b (810.5 mg, 1 mmol) and K2C03 (276.4 mg, 2 mmol) in THF (45 cm3) was stirred for 40 min at 6OoC, then a solution of compound 2 (223.3 mg, 1.1 mmol) in THF (25 cm3) was added at a rate of 10 cm3 h-I. The reaction mixture was stirred overnight at 70 "C before the solvent was removed under reduced pressure, and the residue was dissolved in CHCl,, washed with brine, and the organic layer was dried over MgSO,.After evaporation of the solvent the product mixture was separated by flash-column chromatography (CHC1,- hexane, 10 : 1) to give the pure title product as a solid (1 27 mg, 14%), m.p. 235-237°C; 6,(400 MHz; room temp.) 8.78 and 8.57 [2 x (1 H, s, OH)], 8.39 (1 H, d, 3J7.7, Phth Ar 2-H), 7.80-7.78 (1 H, m, Phth Ar 2-H), 7.74-7.68 (2 H, m, Phth Ar 3- H), 7.47, 7.36,7.24,7.16,7.10, 7.09, 7.06 and 7.02 [8 x (1 H, s, ArH)], 7.26 (2 H, s, ArH), 6.77 (1 H, s, OH), 4.16, 4.13, 4.05, 3.28, 3.90, 3.68, 3.62 and 3.58 [8 x (1 H, d, 'J 12.1-15.9, ArCH'Ar)], 3.49 (2 H, d, 'J 14.4, ArCH,Ar), 1.38, 1.30, 1.24, 1.14 and 1.11 [5 x (9 H, s, Bu')]; 6,(200 MHz; CDCl,CDCl,; 393 K) 8.02 (2 H, br m, Phth ArH), 7.73-7.69 (2 H, m, Phth ArH), 7.30 (4 H, s, ArH), 7.247.10 (2 H, br s, OH), 7.04, 6.99 and 6.91 [3 x (2 H, s, ArH)], 6.37 (1 H, br s, OH), 4.12 and 3.53 [2 x (3 H, d, 'J 14.2, 14.9, ArCH,Ar)], 3.85 and 3.43 [2 x (2 H, d, 'J 14.4 and 13.4, ArCH,Ar)], 1.26 and 1.10 [2 x (18 H, s, Bu')] and 1.21 (9 H, s, Bu'); m/z(FD) 940.7 (M'.Calc. for C63H7207: M, 940.5). 5,11,17,23,29,35-Hexa-tert-butyl-37,38,39,40-tetrahydroxy-41,42-(phthaloyldioxy)calix[6]arene8.4ompound lc (2.9 18 g, 3 mmol) and K2C03 (829 mg, 3 mmol) were suspended in a mixture of THF (75 cm3) and DMF (10 cm3) and the mix- ture was stirred for 40 min at 60 "C. A solution of compound 2 (609 mg, 3 mmol) in THF (25 cm3) was added at a rate of 10 cm3 h-', and the suspension was stirred overnight at 70 "C.The solvent was removed under reduced pressure and the crude product was purified by flash-column chromatography (CHCl,) to afford compound 8 as a solid (1.48 g, 45%), m.p. 305-307 "C (decomp.); 6,(400 MHz; room temp.) 9.96 (2 H, br s, OH), 8.44 and 8.22 [2 x (1 H, br s, OH)], 7.77-7.67 (4 H, m, Phth ArH), 7.48 (1 H, d, 1.7, ArH), 7.43 (1 H, s, ArH), 7.36 (1 H, d, ,J2.O, ArH), 7.24 (3 H, s, ArH), 7.20 (1 H, s, ArH), 7.18 (2 H, d, 1.8, ArH), 7.14 (1 H, d, 2.0, ArH), 7.00 and 6.85 [2 x (1 H, brs,ArH)],4.37,4.23and4.18 [3 x (1 H,d, ,J 10.1-17.1, ArCH,Ar)], 4.1 1-3.93 (2 H, br m, ArCH'Ar), 3.93- 3.77 (2 H, br m, ArCH,Ar), 3.83 (1 H, d, ,J 16.7, ArCH,Ar), 3.65-3.48 (2 H, br m, ArCH,Ar), 3.61 (1 H, d, ,J 13.5, ArCH'Ar), 3.44-3.30 (1 H, br s, ArCH,Ar), 1.42, 1.39,1.33 and I.17 [4 X (9 H, S, Bu')] and 1.36 (18 H, S, Bu'); 6,(200 MHz; CDCl,CDCl,; 393 K) 9.43 (2 H, s, OH), 7.98 (2 H, br m, Phth ArH), 7.90 (2 H, s, OH), 7.68-7.63 (2 H, m, Phth ArH), 7.35 (2 H, s, ArH), 7.09 (6 H, s, ArH), 7.01 (2 H, d, ,J2.2, ArH), 6.77 (2 H, s, ArH), 4.25, 4.04 and 3.64 [3 x (1 H, d, 'J 13.1-13.8, ArCH'Ar)], 4.14 and 3.48 [2 x (2 H, d, ,J 15.7 and 13.5, ArCH'Ar)], 3.97 and 3.60 [2 x (2 H, s, 'J 14.0 and 15.1, ArCH,Ar)], 3.35 (1 H, s, 'J 14.2, ArCH,Ar) and 1.30, 1.26 and 1.09 [3 x (18 H, s, Bu')]; m/z (FD) 1103.3 (M'. Calc. for C74H8608: M, 1102.6). 5,5', 1 1,11', 17,17',23,23'-0cta-tert-butyl-25,25',26,26'-tetra-hydroxy-27,27',28,28'-(pyromellitoyltetraoxy)biscalix[4]arene 9.-KOBu' (440 mg, 4 mmol) was added to a suspension of compound la (1.48 g, 2 mmol) in THF (250 cm3) and the mixture was refluxed for 45 min, before a solution of pyro- mellitoyl tetrachloride (330 mg, 1 mmol) in THF (50 cm3) was added over a period of 4 h.The reaction mixture was kept at 80°C overnight and then the solvent was evaporated. The residue was dissolved in CH,Cl, (160 cm3), the solution was washed with brine, dried over MgSO,, filtered, and evaporated. The crude product was purified by flash-column chro- matography (CHzCl,-diethyl ether, 100: 1) to give the title compound as a solid (430 mg, 29%), m.p. 330°C; 6,(400 MHz) 8.72(2 H, s,Pyrom ArH), 7.69 (4 H, s,OH), 7.35, 7.23, 7.02 and 6.86 [4 x (4 H, d, 2.2-2.3, ArH)], 4.32 and 3.57 [2 x (4 H, d, ,J 13.6, ArCH,Ar)], 4.14, 3.83, 3.67 and 2.89 [4 x (2 H, d, 'J 13.7-14.1, ArCH,Ar)] and 1.29 and 1.17 [2 x (36 s, H, Bu')]; m/z (FAB) 1478.8 (M'.Calc. for C,,H,,oO,,: M, 1478.8). 5,11,17,23-Tetra-tert-butyl-25,26-dihydroxy-27,28-(methyl-enedioxy)calix[4]arene 1la.-A solution of compound la (740.55 mg, 1 mmol) and KOBu' (449 mg, 4 mmol) in THF (200 cm3) was refluxed for 30 min, then a solution of CH,Br, (0.28 cm3, 4 mmol) in THF (50cm3) was added at a rate of 2 cm3h-' to the refluxing mixture. After 1 h of additional reflux the solvent was removed under reduced pressure, the residue was dissolved in CH,CI, (150 cm3) and washed with brine (2 x 50 cm3).The organic phase was dried over MgS0, and the solvent was evaporated off. The crude product was purified by flash- Table 3 Summary of data collection, structure solution and refinement details (a) Crystal data Empirical formula Formula M, Colour, habit Crystal size, mm Crystal system a, b, A c, A a, O A " Y, O v,A3 Space group Z Molecular symmetry F(oo0) Dcalc, g cm3 p, mm-' (b) Data acquisition" Temp., OC Unit-cell reflections (28-range, ") 28,,,(") for reflections hkf Range of reflections Variation in 3 standard reflections Reflections measured Unique reflections Rint Reflections with I na(I), n (c) Structure solution and rejinement Solution method H-atom treatment No. of variables in LS kin w = l/(ozFo + kFoz)R,R,, GoF Density range in final A-map, e A-3 Final shiftterror ratio Second extinction correction 6c C,oH 7001,*0.2CH40 95 1.2 colourless, block 0.15 x 0.15 x 0.25 Triclinic 10.9292(6) 15.0534(10) 16.8534( 14) 94.195(6) 90.044(6) 100.1 7 l(5) 2721.6(3)PT 2 none 1027 1.16 0.07 21 25 (22-28) 48 -12,12/0,17/- 19,19 1% 8530 8529 2187, 2.0 direct methods riding 661 (block-diagonal) 0.0010 0.075,0.076, 1.54 -0.22,0.32 0.02 0.469(099) J.CHEM. soc. PERKIN TRANS. 1 1994 8 C74H860,.0.83C,H,*0.38C6H,, 1200.9 colourless, block 0.30 x 0.60 x 0.65 Monoclinic 14.5554(13) 35.3802(24) 1 5.0160(1 2) 90 99.782( 7) 90 7620(1) n1tn 4 none 2617 1.05 0.07 21 25 (30-36) 48 0,16/0,40/-17,17 1% 12 421 11 913 0.008 4028, 3.0 direct methods riding 878 (block-diagonal) 0.0015 0.072,0.097, 1.96 -0.36,0.41 0.07 2.55(39) Data collection on an Enraf-Nonius CAD4 diffractometer with graphite-monochromatized Mo-Ka radiation (A0.7093A).All calculations were done on a Silicon Graphics 4D-35TG computer system. column chromatography to yield the title compound as a solid (80 mg, 12%) m.p. 247-249 "C; 6,(200 MHz; CDCl,CDCl,; 363 K) 7.06 (4 H, pseudo-s, ArH), 7.02 and 6.98 [2 x (2 H, d, 4J 2.1, ArH)], 4.94 (2 H, s, OH), 3.92, 3.85 and 3.77 [3 x (2 H, s, CH,)], 3.82 (4 H, s, ArCH,Ar) and 1.23 and 1.17 [2 x (18 H, s, Bur)]; m/z (EI) 660.2 (M+.Calc. for C45H5604: M, 660.4). 5,11,17,23-Tetra-tert-butyl-25-(carboxymethoxy)-26,27,28-trihydroxy calix[4]arene by Hydrolysis of Compound 6a.-A mixture of 1 mol dm-, KOH (1.74 cm3, 1.74 mmol), compound 6a (100 mg, 0.116 mmol), MeOH (25 an3)and water (2 cm3) was refluxed overnight. The clear solution was cooled and added dropwise to a mixture of ice and 1 mol dmP3 HCl to give a precipitate, which was washed with water to yield the title 5,11,17,23,29,35-Hexa-tert-butyl-37,38,39,~-tetrahydroxy-compound (81 mg, 99%) as a solid, m.p. 188-191 "C; m/z (EI) 41,42-(methylenedioxy)calix[6]arene 1lb.-A mixture of com- pound lc (972.6 mg, 1 mmol) and Cs,CO, (977 mg, 3 mmol) in DMF (125 an3)was stirred for 30 min at room temperature. The mixture was warmed to 40 "C and a solution of CH,BrCl (0.2 cm', 3 mmol) in DMF (50cm3) was added at a rate of 6 cm3 h-'.The addition was repeated 4 times, the solvent was evaporated off under reduced pressure and the product mixture was separated by flash-column chromatography (CHCl,) to afford the title compound as a pure solid (149 mg, 15%), m.p. 302-304 "C (decomp.); 6H(200 MHz) 9.1 1 and 7.83 [2 x (2 H, s, OH)], 7.21 (4 H, s, ArH), 7.20, 7.19, 7.15 and 7.07 [4 x (2 H, d, 4J 2.2-2.5, ArH)], 5.10 (2 H, br s, OCH,O), 3.92 and 3.87 [2 x (6 H, s, ArCH,Ar)] and 1.32, 1.316 and 1.25 [3 x (18 H, s, Bu')]; m/z (FD) 984.7 (M+. Calc. for C6&406: M, 984.6). 706.5 (M+. CdC. for C46H5806: M, 706.4). 5,11,17,23-Tetra-tert-butyl-25-[(ethoxycarbonyl)methoxy]-26,27,28-trihydroxycalix[4]arene.-The calixC4larene mono-acid thus obtained (42 mg, 0.06 mmol) was esterified by being refluxed in absolute ethanol (30 cm3) in the presence of conc.H2S04. Work-up gave the title compound (39.7 mg, 91%) as a solid, m.p. 269.5-271.5OC; 6,(400 MHz) 10.23 (1 H, s, OH at C-27), 9.26 (2 H, s, OH at C-26, C-28 OH), 7.09 (2 H, s, ArH), 7.05 (4 H, s ArH), 6.98 (2 H, d, 4J 2.4, ArH), 4.88 (2 H, s, OCH,CO), 4.48, 4.30, 3.43 and 3.42 [4 x (2 H, d, 'J 12.6-14.1, ArCH,Ar)], 4.40 (2 H, q, 7.1, CH,Me), 1.39 (3 H, t, 7.1, CH,Me), 1.23 and 1.19 [2 x (9 H, s, Bu')] and 1.20 (18 H, s, Bu'); m/z (EI) 734.4 (M'. Calc. for C48H6,06: M, 734.5). J. CHEM. SOC. PERKIN TRANS. I 1994 5,11,17,23-Tetra-tert-butyl-25,26-bis(carboxymethoxy)-27,28-dihydroxycalix[4]arene (syn Isomer) by Hydrolysis of Com-pound 6b.-A mixture of compound 6b (90 mg, 0.095 mmol) and 1 mol dmP3 KOH (1.9 cm3) in MeOH-water (33 cm3-3 cm3) was refluxed overnight.The crude product was purified by flash-column chromatography (CHC1,-MeOH, 5 :1) to give the title compound as a solid (52 mg, 72%), m.p. 275-277 "C (decomp.); m/z (FD) 764.5 (M'. Calc. for C48H6008: M, 764.4). 5,11,17,23-Tetra-tert-butyl-25,26-bis(carboxymethoxy)-27,28-dihydroxycalix[4]arene (anti Isomer) by Hydrolysis of Com-pound &.--A suspension of compound 6c (90 mg, 0.095 mmol) in a mixture of MeOH-water (25 cm3-3 an3)and 1 mol dm-3 KOH (3.77 cm3) was refluxed for 2 days. Work-up as described for compound 6a gave the title compound as a solid (60 mg, 83%), m.p.240-245 "C (decomp.); m/z (FD) 764.5 (M'. Calc. for C48H6008: M, 764.4). Structural Analysis for Calixarenes 6cand 8.-Single crystals of compound 6c were obtained by gas-phase diffusion of n- hexane into a solution of compound 6c in benzene. Single crystals of compound 8 were obtained from a solution in CH,Cl, by gas-phase diffusion of ethanol. Both structures were solved by direct methods using SHELXS8644 which revealed the non-hydrogen atoms of the calixarene core, and were refined using the NRCVAX 45 suite of programs. The remaining non-hydrogen atoms were located in subsequent difference Fourier syntheses. Details of the X-ray experimental conditions, cell data, data collection and refine- ment for molecules 6c-0.2MeOH and 8*0.83C7H8=0.38C6HI4 are summarized in Table 3.Additional material available from the Cambridge Crystal- lographic Data Centre comprises atom coordinates and thermal parameters.* Copies of the structure factor listing are available from the authors. Conclusion.-Reaction of tert-butyl-calix[4]- and -calix[6]- arene with phthaloyl dichloride may be used, in principle, to protect the OH groups of two adjacent phenolic units in a reversible way, while with tert-butylcalix[5]arene the bridging was observed only between two distal OH groups. Further alkylation of the remaining OH groups is possible but, in general, the introduction of the phthaloyl groups as well as the further alkylation leaves room for improvements, while the ester groups can be cleaved again in a clean way.Acknowledgements These studies were supported by the Deutsche Forschungs- gemeinschaft and the European Community. G. F. thanks NSERC Canada for Grants in Aid of Research. We are grateful to Prof. C. D. Gutsche, who kindly provided us with an improved procedure for the preparation of tert-butyl-~alix[5]arene'~ prior to publication and to Prof. M. A. McKervey for sending us a first sample of this compound. *See Instructions for Authors, J. Chem. Soc., Perkin Trans. 1, 1994, issue 1. References 1 For a recent review see: J. D. van Loon, W. Verboom and D. N. Reinhoudt, Org. Prep. Proced. Int., 1992,24,437. 2 K. Iwamoto, K. Araki and S. Shinkai, Tetrahedron, 1991,47,4325.3 S. Caccamese and S. Pappalardo, Chirality, 1993,5, 159. 4 A. M. King, C. P. 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