Selective ether cleavages: simple routes yielding di- and tri-functional hexaalkoxytriphenylenes

摘要

J. CHEM. SOC. PERKIN TRANS. 1 1995 Selective ether cleavages: simple routes yielding di- and tri-functional hexaalkoxytriphenylenes Fritz Closs,"Lukas HauBling," Philippe Henderson: Helmut Ringsdorf *9b and Peter Schuhmacher a BASF AG, 0-67056 Ludwigshafen, Germany Institut fur Organische Chemie der Universitat Mainz, J. J.-Becher- Weg 18-20, 0-55099 Mainz, Germany Discotic hexasubstituted triphenylene derivatives represent a promising class of materials, e.g. with respect to their photoconductive properties. To tailor the processibility and mesophase behaviour of such materials specifically functionalized cores as precursor molecules for discotic oligomers, polymers and networks or amphiphiles are required. The paper presents various synthetic strategies, all based on selective ether cleavage methods, leading to new highly functionalized triphenylenes.2,3,6,7,10,11-Hexaalkoxytriphenylenes represent one of the most studied class of discotic liquid crystals. Derivatization of these highly symmetric molecules is necessary for varying the molecular architecture as well as for tailoring mesophase prop- erties and processibility. The molecular engineering towards more advanced discotic triphenylenes started with the prepar- ation of discotic main chain and side group polymers' thus leading to enhanced mesophase stabilities and mechanical properties. The synthesis of mono- and di-functional triphenvl- ene monomers was achieved by statistical methods. Meanwhile discotic liquid crystals-in particular triphenylenes-have re-ceived increased attention due to the rapid charge migration along the columnar stacks2 and the fabrication of nano-size materials by mono- and multi-layer technique^.^,^ For the further elaboration of this novel class of materials new synthetic strategies are required for matching the demands of the more sophisticated investigations involving the tailoring of proces- sible materials with defined mesophase and mechanical proper- ties.In a first approach we reported s on the improved synthesis of monofunctional discotic triphenylenes as precursor molecules for oligomeric and polymeric discotics. The next step for the exploration of the potential usefulness of discotic columnar triphenylenes involves the preparation of highly functionalized triphenylene cores e.g.for the preparation of discotic columnar networks or polymerizable amphiphiles. Indeed different re- search groups are presently working on new synthetic routes 5-7 allowing the preparation of compounds that were until recently available only in poor yields or were even unavailable. Until now 2,3,6,7,10,11 -hexaalkoxytriphenylenes have been synthe- sized by trimerization of an o-dialkoxybenzene derivative. Via this route a statistical mixture of triphenylenes carrying at least two different alkoxy groups is available. 1*9A limitation results from the reaction conditions that are incompatible with some interesting functionalities, e.g.hydroxyaryl groups, olefins, some crown ethers and other cationic complexants. A new strategy described by Borner and Jackson passing through a terphenyl intermediate allows the preparation of highly functionalized triphenylene cores (Scheme 1).This sophisticated method is particularly useful for the preparation of triphenylene cores with less than six alkoxy groups. Similarly unsymmetrically substituted triphenylenes have been obtained using arylboronic acids. A simpler approach for functionalized triphenylenes (Scheme 2) has been recently described by Boden et al. ' and Henderson et aL5 This so called 'biphenyl route' allows the possibility of large scale preparation. However this reaction proceeds under the same conditions as the classical trimerization and thus R3 3 Terphyl derivrtive R'DaclR2 + R6Qac'-Br Scheme 1 Synthesis of triphenylene derivatives uiu the 'terphenyl route' OR1 OR'&1' OR' I OR' OR' Scheme 2 Synthesis of triphenylene derivatives uiu the 'biphenyl route' suffers from similar functional limitations.It is consequently necessary to introduce the desired groups at the last step. In the present paper we describe different methods of selective ether cleavage allowing the synthesis of triphenylenes carrying two or three different alkoxy groups with a definite regiochemistry. The triphenylene cores used as starting material are always simple compounds easily available either by the classical trimerization or by the 'biphenyl route'. In order to simplify the following discussion the pentyloxy groups will not be taken in account as 'functional groups'.Thus, for example, compounds 1 and 5 will be considered as difunctional triphenylenes and compounds 13a and 17 as trifunctional cores. Preparation of difunctional triphenylenes The ability of lithium diphenylphosphide (Ph,PLi) to select- ively cleave methyl, ally1 and benzyl aryl ethers is well known from the literature." It has been previously shown that the selectivity can be exploited to afford the 2-hydroxy-3,6,7,10,11- pentapentyloxytriphenylene (95%) and the 2,7-dihydroxy- 3,6,10,11-tetrahexyloxytriphenylene (yield not reported) ' (Scheme 3). By extending this procedure 2,6-dihydroxy-3,7,10,11 -tetra- pentyloxy-, 2,7-dihydroxy-3,6,10,1l-tetrapentyloxy-and 2,ll- dihydroxy-3,6,7,lO-tetrapentyloxy-triphenylenehave been pre- pared while 2,3-dihydroxy-6,7,10,11 -tetrapentyloxytriphenyl-ene has been isolated only in poor yield ( -20%) probably due to the greater instability of the intermediate ortho-dianion and the lower reactivity of the second methoxy group.Indeed, the cleavage of the second methyl requires the use of a large excess of Ph,PLi and is much slower than for the other isomers. As previously shown it is possible to take advantage of this behaviour to prepare a triphenylene carrying two different functional groups. It is worthwhile reporting that the cleavage step is compatible with an olefinic group [Scheme 4, eqn. (l)] while hydroxyalkyl chains are partially cleaved [Scheme 4, eqn.(2)]. Dihydroxytetrapentyloxytriphenylenes are key intermediates for the synthesis of polymerizable derivatives and amphiphiles 1 0- 0- t pento Opent 0- 3 J. CHEM. SOC. PERKIN TRANS. 1 1995 h which can also be polymerized to main chain polymers (e.g. polymalonates 4b)(Scheme 5). Since 2,3-dihydroxy-6,7,10,11-tetrapentyloxytriphenylene which is the target precursor molecule for the preparation of difunctionalized compounds carrying the same functionality in the 2,3 position, is not available by the described selective ether cleavage we followed a different approach. The biphenyl coupling with o-dihydroxybenzene does not yield the corresponding 2,3-dihydroxytriphenylene but one free phe- nolic group is tolerated by the reaction conditions providing the simplest approach for monofunctionalized derivatives.2,3-Difunctionalized cores can be obtained starting from the 2-hydroxy-3-methoxy-6,7,10,11-tetrapentyloxytriphenylene 8 which is synthesized from tetrapentyloxybiphenyl and o-methoxyphenol (7 1 % yield) according to the coupling conditions previously described. It is possible to cleave the 2 1A3 x =1,2 PhZPLi 70-95%J 7\ (OPent)(cx Scheme 3 Preparation of mono- and di-hydroxytriphenylene cores by selective methyl aryl ether cleavage OPent 2 OPent (2) OH pepto 0-n 22.3 R=H.Me n =53 3 7 Scheme 4 Functional compatibility with the ether cleavage J. CHEM. SOC. PERKIN TRANS. I 1995 831 ?Pent i, BrCH&-OSiBu%¶e, ii.ByNF 81% OPent OPent 4 ?Pent 6Pent 6 7 Scheme 5 Synthesis of discoid polymerizable, 7, or amphiphilic, 56, triphenylenes OPmt OPmt i. BuLi ii, BBr,Pent0 8 9 52% Scheme 6 Preparation of the 2,3-dihydroxy-6,7,lO,ll-tetrapentyloxytriphenyleneby ether cleavage with intramolecular assistance 9 10 11 Scheme 7 Synthesis of a 2,3-difunctionalized amphiphilic triphenylene methoxy group with BBr, by means of intramolecular degradation. The functionalization can be carried out by using assistance (Scheme 6). a reactive trifluoromethanesulfonate (triflate) (Scheme 7). Employing the same procedure starting from the 2-hydroxy- 3,6,7,10,11-pentapentyloxytriphenylene,the yield is sometimes reduced (39-5 1%).The 2,3-dihydroxy derivative 9 is unstable Preparation of trifunctional triphenylenes even at low temperature and has to be functionalized rapidly Triphenylenes carrying three polymerizable groups are of par- after isolation. We were interested in the preparation of the ticular interest as cross-linkers for the synthesis of discotic amphiphile 11. However alkylation by 1,2-bromoethanol is too elastomers and networks. They are more easily handled than the slow (75 OC, 24 h) and the dihydroxytriphenylene 9 undergoes corresponding hexafunctional derivatives and the mesophase 832 J. CHEM. SOC. PERKIN TRANS. 1 1995 ?Pent ?Pent pento-OPmt ilR' L12 13a R' = H and R2= Pent (38%) Scheme 8 Simple synthesis of trihydroxytripentyloxytriphenylenes 13b R' = Pent and R2= H (47%) stability is less affected by the functionalization.For this reason we have developed a one step synthesis leading to trihydroxy- tripentyloxytriphenylenesstarting from the easily available 2,3,6,7,10,11-hexapentyloxytriphenylene12 (HPT).? Using a very bulky Lewis acid such as 9-bromo-9-borabicyclo[3.3.1]-nonane (9-BrBBN) l2 allows the cleavage of ohly one pentyl group per benzene ring (Scheme 8). The resulting symmetric (13a) and non-symmetric(l3b) trihydroxytripentyloxytriphenyl-enes can be very easily separated by a simple single chromato- graphy on silica gel. It has to be noted that the corresponding mixture of symmetric and non-symmetric trimethoxytripentyl- oxytriphenylenes immediately available by trimerization of o-pentyloxyanisole is extremely difficult to separate by chromato- graphy.9-BrBBN can also be used to provide mono- and di-func- tional derivatives by a statistical approach giving better yields than those previously described.This procedure allows the reaction to be scaled up to kilogram amounts. The two derivatives 13a and 13b can be converted by classical alkylations (Scheme 9) into different trifunctional derivatives OPent OPent OPent OPent RX = Me1 R=Me (86%) 14 = Br-(CH2),HC=CH2 R = (CH&HC=CHZ (78%) 15 Scheme 9 Synthesis of trifunctional triphenylenes (cross-linkers for liquid crystalline networks, derivatives for phase behaviour studies, side-on amphiphiles). The triolefin 15can be used as cross-linker for the preparation of networks having a polysiloxane backbone.The following two examples illustrate how highly functional- ized triphenylenes can be obtained by using either of the two ether cleavages. The C,-symmetric trime thoxytripen tox ytri- phenylene 14a is a useful precursor for the regiocontrolled synthesis of a highly functionalized cross-linker of interest for the preparation of discotic elastomers with permanent director orientation. l3 The addition of 2.5equiv. of Ph,PLi to 14a yields t HPT is synthesized by the same method and in the same yield as the hexahexyloxytriphenylenein ref. 7. a mixture of mono-, di- and tri-hydroxytriphenylenes in which the dihydroxy derivative is the major compound. When using a larger excess of Ph,PLi, degradations are observed and the 2,6,10-trihydroxy-3,7,11-tripentyloxytriphenyleneis never iso- lated in good yield.The mixture of mono-, di- and tri- hydroxytriphenylenes is alkylated with the 8-bromooct-I-ene l4 and the resulting compounds are separated on silica gel (Scheme 10). The last methoxy group of 17 is then cleaved by the same reagent (Ph,PLi) to give the corresponding phenol 18. The latter can be easily converted in two steps into the methacrylate 19 (Scheme 1 1). Viahydrosilylation to polysiloxane backbone it has been shown that the olefinic double bond reacts 70 times faster than the methacrylate thus giving a preformed elastomer which can be oriented by a mechanical field.', The slow reaction of the methacrylate fixes the network anisotropy providing monodomain samples.The regiocontrol provided by the above described synthesis is not always necessary and a shorter procedure yielding regio- isomeric mixtures could be of interest. To achieve this goal, we have protected the hydroxy group of the 2-hydroxy-3,6,7,10,11- pentapentyloxytriphenylene 20 by a bulky silyl group. This re- action furnishes a triphenylene core 21 on which the 9-BrBBN is able to cleave only two pentyl chains (no side-product re- sulting from triple cleavage has been observed) thus showing the principle of protection of a benzene ring by steric hindrance (Scheme 12). The resulting dihydroxy derivatives 22a-d could give a mixture of compounds 13a and 13b by simple desilylation but could also be used to prepare 18.For the latter case a mixture of four regioisomers should be isolated however the three functional groups will always be distributed on the three different benzene rings. The advantage of the suggested syn- thesis is that the overall yield starting from the o-dipentyloxy- benzene should be much higher than for the procedures pre- sented in Schemes 8-11 even if the two regioisomers 13a and 13b (precursors of 14) are used together. In addition compound 22a can be easily separated from the other regioisomers during the column chromatography. This derivative could be used as precursor for the synthesis of a polymerizable amphiphile (Scheme 13). Conclusions The present paper demonstrates the usefulness of different methods of selective ether cleavage to prepare a large series of highly functionalized triphenylenes starting from simple hexa- alkoxy substituted cores.The compounds presented are all of potential interest for basic studies or for the preparation of J. CHEM. soc. PERKIN TRANS. 1 1995 833 OPent ?Pent R20&0 PentO i, Br-(CI12)+H=CH2ii, Silica gel chromatography OMe Y OR' OPent \ ?PentMcoa--(CH2)6-CH=CH2 14a 16a R' =R2 = Me 16b R' =R2 = H 16c R' = H, R2 = Me PentO 17 Pent Scheme 10 Double functionalization of the symmetric derivative 14a with Ph,PLi as selective ether cleavage agent 17 xHoq78% Pent0 ' OPent I O-(CH&-cH=cH2 OPent 29 18 Tfosipj3100%I 41 -opent \A OO"Y Pento-4' opent Okt 21 19 9-BrBBN 77%IScheme 11 Preparation of a highly functionalized triphenylene core useful as a cross-linker for elastomer synthesis liquid crystalline polymers and networks.In addition we think that the developed strategies could be extended to other poly- aromatic systems, e.g. dibenzopyrenes or truxenes. Experimental Phase types and transitions were determined using polarizing microscopy and a DSC 7 (Perkin-Elmer) with heating and 22 cooling rates of 10 K min-'. 'H NMR were recorded on a 200 a R' =R4 = Pent &R2 =R3 =H (17%) MHz FT-NMR spectrometer AC-200 Bruker; Jvalues are given b R' =R3 =Pentand R2 =R' =H in Hz. IR spectra were measured on an FT-IR 5 DXC Nicolet c R'=R3 =H mdR2= R4=Pent }03%) spectrometer.The mass spectrometer used was a Finnigan d R' =R4 =H dR2= R3 =Pent(27.5%) MAT 95. Scheme 12 Double ether cleavages by steric protection of a single benzene ring Synthesis of 2,lldihydroxy-3,6,7,1O-tetrapentyloxytri-mp 74-82 "C (Found: C, 74.25; H, 8.9. C24H3404 requires C, phenylene4 74.57; H, 8.87); 6,(200 MHz; CDCl,) 7.08-6.88 (6 H, m, ArH), The dimethoxydipentyloxybiphenyl(mixture of 3 isomers) was 4.06and4.02(4H,2 x t, J6.6and6.8,0CH2),3.91 and3.88(6 prepared from o-pentyloxyanisole via iodination and Ullmann- H, 2 x s, OCH,), 1.92-1.78 (4 H, m, OCH,CH,), 1.50-1.37 [8 coupling following the same procedure as for the synthesis of H, m, OCH,CH,(CH,),] and0.92 [6 H, t, J6.8, O(CH,),CH3]; to give a mixture of isomers m/z (EI) 387 (M+,3,3',4,4'-tetrapentylo~ybiphenyl,~ 100%).(77% on a 150 g scale), R, 0.25 (CH,Cl,-light petroleum, 2: 1) 2,ll -Dimethoxy-3,6,7,lO-triphenylenewas prepared via the R2 OPent I /" .O .-& R' = hyhphilic group R~ = polymerisable group 'OPent R' Scheme 13 Possible preparation of a polymerizable amphiphile de-rived from triphenylene 'biphenyl route' by coupling the dimethoxydipentyloxybi-phenyl prepared above with dipentyloxybenzene. The 2,ll-isomer was separated from the 2,6-and the 2,7-isomers by columnchromatography (CH,CI,-light petroleum, 2 :1) R,(2, 11) 0.5, R,(2,6 and 2,7) 0.7, at the 10 g scale: 9% of 2,ll-isomer and 30% of 2,6-and 2,7-isomers. Data for the 2,ll -isomer mp 106 "C; 6,(400 MHz; CDCl,) 7.82, 7.81 and 7.80 (6 H, 3 x s, ArH), 4.24 and 4.22 (8 H, 2 x t, J6.8 and 6.5, OCH,), 4.08 (6 H, s, OCH,), 2.03-1.88 (8 H, m, OCH,CH2), 1.61-1.39 [16 H, m, OCH,CH,(CH,),] and 0.96 [12 H, t, J7.O,O(CH2),CH,]; m/z (EI) 632 (M+, 100%).The cleavage of the two methyl groups was achieved fol-lowing the previously described method. 5,1 A mixture of 2,ll-dimethoxy-3,6,7,10-triphenylene(1.60 g, 2.5 mmol) and BuLi (7.5 mmol, 3 equiv.) and diphenylphosphine (7.5 mmol, 3 equiv.) was refluxed until cleavage was completed ( -1 h). The reaction was monitored by TLC [CH,Cl,-hexane, 3 :2, &(reagent) 0.4, R,(product) 0.21. The reaction mixture was purified by silica gel chromatography to give the diphenol 4 (1.15 g, 7573, mp 142.5 "C; vm,,(KBr)/cm-' 3540 and 3400 (free and bonded OH) and 2870 and 2950 (CH arom.); dH(4O0MHz; CDC1,) 7.92,7.79 and 7.73 (6 H, 3 x s, ArH), 5.85 (2 H, s, OH), 4.26 and 4.21 (8 H, 2 x t, J 6.4 and 6.5, OCH,), 2.05-1.85 (8 H, m, OCH,CH,), 1.61-1.39 [16 H, m, OCH,CH,(CH,),] and0.95 [12 H, t, J7.0, O(CH,),CH,]; the structure was confirmed by NOE spectro-scopy: ArHirrad(7.92) --+OHenh,OHirrad---ArHenh(7.92) and OCH,""' (4.26), ArHirrad(7.79) -ArHenh(7.73) and OCH,enh (4.21), ArHirrad (7.73) --, ArHenh (7.79) and OCHzenh(4.26); m/z(El) 604 (M', 17%) and 57 (100, Butyl').Synthesis of the 2,6-and 2,7dihydroxytetrapentyloxy-triphenylenes A mixture of 2,6-and 2,7-dimethoxytetrapentyloxytriphenyl-enes was submitted to the same ether cleavage conditions as for the 2,ll-isomer.The two products (83% global yield) were separated by silica gel chromatography (CH,Cl,-hexane, 3 :2) to give the 2,6-isomer (0.73 g, 14%), R, (CH,Cl,-hexane, 4: 1) 0.65; mp 82.5 "C and the 2,7-isomer (3.51 g, 6673, R, (CH,CI,-hexane, 4: 1) 0.56, mp 180 "C; 6,(200 and 400 MHz) and m/z (EI) in agreement with the suggested structures. Synthesis of amphiphiles2,l l-bis(6-hydroxyhexyloxy)-3,6,7,10-tetrapentyloxytriphenylene5 and 2,1l-bis(3-hydroxypropoxy)-3,6,7,lO-tetrapentyloxytriphenylene6 Alkylation was performed following the previously described procedure. l4 Both non protected and silicon protected o-bromo alcohols can be used for the alkylation step but the protected one allows a longer reflux time, sometimes necessary to com-J.CHEM. SOC. PERKIN TRANS. I 1995 plete the reaction, without increasing the risk of polyether formation. The reactions were monitored by TLC. The mixtures were then extracted with CH,Cl, and dried over MgSO,. The crude disilylated intermediate was dissolved in THF (to give a solution of 0.05 mol drn-,) and Bu,NF (2 equiv. per silyl group) was added. The reaction was heated for 2 h at 50 "C. CH,Cl, was then added and the mixture was washed with water. The organic phase was dried over MgSO,. The crude amphiphiles 5 and 6 were purified by silica gel chromatography. For 5, eluent: CH,Cl,-AcOEt, 3 :2, R, 0.3 gives pure com-pound 5 (105 mg, 81% from 95 mg of 4); phase behaviour: c 65 "C (& 55 "C) i (Found: C, 74.4; H, 9.5. C50H7608requires C, 74.59; H, 9.5%); dH(200 MHz; CDCI,) 7.81 (6 H, s, ArH), 4.21 (12 H, t, J6.6, ArOCH,), 3.67 (4 H, t, J5.8, CH,OH), 2.05-1.85 (12 H, m, OCH,CH,), 1.70-1.30 [28 H, m, OCH,CH,-(CH,),, or ,,I and 0.95 (12 H, t, J 7.0, CH,); m/z (FD) 806 ([M + l]', 100%).For 6, eluent: CH,CI,-AcOEt, 1 : 1, R, 0.35 gives pure com-pound 6 (0.84 g, 56% from 1.26g of 4); phase behaviour: c 87 "C D,99 "C D,118 "C i; 6,(200 MHz; CDCl,) 7.83, 7.81 and 7.78 (6 H, 3 x s, ArH), 4.42 [4 H, t, J 5.7, OCH,(CH,),OH], 4.22 and4.21(8H,2 x t,J6.5and6.7,0CH2Bu),3.96(4H,t,J5.2, CH,OH), 2.24-2.15 (4 H, m, OCH,CH2CH,0H), 1.98-1.85 (8 H, m, OCH,CH,Pr), 1.63-1.37 [16 H, m, OCH,CH,-(CH,),] and 0.96 (I2 H, t, J 6.9, CH,); m/z (FD) 721 ([M + l]', 100%). Synthesis of 2,ll -bis[3-(acryloyloxy)propoxy] -3,6,7,10-tetrapentyloxytriphenylene7 Compound 6 (0.75 g, 1.04mmol), diisopropylethylamine (0.544 cm3, 3.12 mmol), acryloyl chloride (0.28 g, 3.12 mmol) and 2,6-di-tert-butyl-p-cresol (70 mg, 0.32 mmol) were added at 0 "C under argon to CH,Cl, (20 cm3).The reaction was stirred for 2 h at room temperature and then washed with K2C03.The organic phase was dried over MgSO,.The crude diacrylate was purified by silica gel chromatography (CH,Cl,-AcOEt, 150: 1) to give pure diacrylate 7 (0.83 g, 96%), R,(CH,Cl,-AcOEt, 100: 1) 0.5; mp 86OC (Found: C, 72.5; H, 8.3. C,,H,,O,, requires C, 72.43; H, 8.26%);6,(200 MHz; CDCl,) 7.85 and 7.82 (6 H, 2 x s, ArH), 6.43 (2 H, dd, J,,,,, 17.1, J,,, 1.5, COCHKH,), 6.13 (2 H,dd,Jcis10.2,J,,,,, 17.2,COCH=CH2), 5.82 (2 H, dd, Jcis10.3,J,,, 1.6,COCHXH,), 4.48 [4 H, t, J6.4, OCH,(CH,),OCO], 4.33 [4 H, t, J 6.2, O(CH,),CH,OCO], 4.22 and 4.21 (8 H, 2 x t, J6.5 and 6.6,0CH2Bu),2.33-2.27 (4 H, m, OCH,CH,CH,OCO), 2.01-1.87 (8 H, m, OCH,CH,Pr), 1.59-1.39 [16 H, m, O(CH,),(CH,),] and 0.96 (12 H, t, J7.0, CH,); m/z (FD) 830 ([M + l]', 100%).Synthesis of 2,3-dihydroxy-6,7,10,1 l-tetrapentyloxytri-phenylene 9 Butyllithium (1.5 mol dm-, in hexane; 0.26 cm3,0.39 mmol) was added at -78 "C and under argon to a solution of compound 8 (0.24 g, 0.39 mmol) CH,Cl, (10 cm3). BBr, (0.43 cm3, 0.39 mmol) was then added to the mixture at -78 "C. The mixture was stirred for 90 min at room temperature and then the reaction was quenched with water and again stirred for 30 min.The mixture was extracted with CH,CI, and the organic solution was dried over MgS0, to afford the crude diphenol9 which was purified by silica gel chromatography (CH,Cl,-AcOEt, 1 :O then 19: 1) to give the pure compound (122 mg, 52%) as a white solid which cannot be stored, R,(CH,Cl,) 0.1; mp 130 "C; 6&00 MHz; CDC1,) 7.87, 7.78 and 7.75 (6 H, 3 x s,ArH),5.66(2H,s,OH),4.20and4.15(8H,2x t,J6.6 and 6.6, OCH,), 2.05-1.85 (8 H, m, OCH,CH,), 1.65-1.35 [16 H, m, O(CH,),(CH,),] and 0.93 and 0.94 (12 H, 2 x t, J 7.0 and 7.0, CH,); m/z (EI) 604 (M', 100%). J. CHEM. SOC. PERKIN TRANS. I 1995 Synthesis of 2,3-bis(2-benzyloxyethoxy)-6,7,10,11-tetra-pentyloxytriphenylene 10 Compound 9 (0.100 g, 0.17 mmol) and pentan-2-one (4 cm3) were introduced into a two necked flask equipped with a reflux condenser under argon.After complete dissolution, K,CO, (0.9g, 6.6 mmol) and benzyloxyethyl trifluoromethanesulfonate (0.141 g. 0.5 mmol) were added and the reaction was heated at 75 "C for 1 h. The reaction was monitored by TLC. The reaction mixture was extracted with CH,CI2 and the organic solution was dried over MgSO, to afford the crude dibenzyl derivative 10 which was purified by silica gel chromatography (CH,CI,-hexane, 3:2 then 4: 1) to give the pure product (93 mg, 65%), R,(CH,Cl,) 0.44; phase behaviour: c' 71.5"C (Dh 62 "C) i (Found: C, 77.2; H, 8.4. C,,H,,O, requires C, 77.03; H, 8.31%); SH(200 MHz; CDCI,) 7.92, 7.81 and 7.79 (6 H, 3 x s, triph ArH), 7.50-7.20 (10 H, m, benz ArH), 4.66 (4 H, s, OCH,Ph), 4.42 (4 H, t, J 4.7, OCH,CH,OCH,Ph), 4.21 and 4.16 (8 H, 2 x t, J 6.6 and 6.6, OCH,Bu), 3.93 (4 H, t, J 5.0, OCH,CH,OCH,Ph), 2.0C1.85 (8 H, m, OCH,CH,Pr), 1.65-1.35 [I6 H, m, O(CH,),(CH,),] and0.95 (12 H, t, J7.1.CH,); nr/z (FD) 873 (M ', 100%). Synthesis of 2,3-bis(2-hydroxyethoxy)-6,7,10,11-tetra-pentyloxytriphenylene 1 1 Compound 10 (80 mg, 0.092 mmol) and cyclohexene (1 cm3) were introduced into a two necked flask equipped with a reflux condenser and flushed with argon. After complete dissolution, ethanol (2 cm3) and Pd(OH),/C (20%; 10 mg) were added and the reaction was heated at 75 "C for -4 h. The reaction was monitored by TLC. The reaction was then diluted with CH,Cl, and filtered through Celite.Purification by silica gel chromato- graphy (CH,CI,-AcOEt, I : 1 then 0: I) gave amphiphile 11 (49 mg, 78%). R,(AcOEt) 0.65; phase behaviour: c 128 "C D, 139 "C i(Found: C. 72.4; H, 8.8. C42H6008 requiresC, 72.80; H, 8.73%); SH(200 MHz; CDCI,) 7.82,7.76 and 7.70 (6 H, 3 x s, ArH), 4.30 (4 H, t, J 4.1, OCH,CH,OH), 4.21 and 4.16 (8 H, 2 x t, J 6.6 and 6.6, OCH,Bu), 4.04 (4 H, br s, OCH,CH,OH), 3.68 (2 H, br s, OH), 2.00-1.85 (8 H, m, OCH,CH,Pr), 1.65-1.35 1116 H, m, O(CH,),(CH,),] and 0.96 (12 H, t, J 7.0, CH,); mi: (EI) 693 (M + . 1OUX). Synthesis of 2,6,10-trihydroxy-3,7,11-tripentyloxytri-phenylene 13a and 2,6,1l-trihydroxy-3,7,1O-tripentyl-oxytriphenylene 13b 2,3,6,7,10,11-Hexapentyloxytriphenylene 12(0.300g,0.4mmol), CH,CI, (3 cm3) and 9-bromo-9-borabicyclo[3.3. Ilnonane (9- BrBBN) (1 mol dm-, in CH,CI,; 1.81 cm', 1.8 mmol, 4.5 equiv.) were introduced into a flask under argon.The reaction mixture was stirred for 30 h at room temperature and then slowly quenched by the addition of 2-aminoethanol (0.1 1 cm', 1.8 mmol). Water was added to the mixture which was then extracted with CH,Cl,. The organic phase was dried over MgSO, and purified by silica gel chromatography (CH,CI,- hexane, 3 :2 then I :0)to give pure compounds 13a (81 mg, 38%) and 13b (101 mg, 47%). Compound 13a, R,(CH ,CI,-hexane 3 :2) 0.51 ; mp 140 "C; v,,J KBr)/cm 3540 and 3450 (free and bonded OH) and 2870, 2950 and 2970 (CH arom.); dH(200 MHz; CDCI,) 7.90 and 7.77 (6 H, 2 x s, ArH), 5.88 (3 H, s, OH), 4.24 (6 H, t, J6.6, OCH,), 2.05-1.85 (6 H, m, OCH,CH,), 1.65-1.35 [I2 H, m, O(CH,),- (CH,),] and 0.96 (9 H, t, J6.9, CH,); m/z (EI) 534 (M+,100%).Compound 13b, R,(CH,CI,-hexane 3 :2) 0.16; mp 146 "C; 6H(200MHz;CDC13)7.91,7.90,7.76,7.70and7.69(6H,5x s, ArH),5.87,5.85and5.84(3H,3x s,OH),4.26and4.23(6H,t, J6.3 and 5.3. OCH,), 2.05-1.80(6 H, m, OCH,CH,), 1.65-1.35 [I2 H, m. O(CH,),(CH,),] and 0.96 (9 H,t, J 7.0, CH,); m/z (El) 534 (M', 100%). 835 Statistic preparation of mono- and di-functional triphenylenes by means of 9-BrBBN Compound 12 (1.1 kg, I .48 mol), CH,CI, (3 dm3) and 9-BrBBN (1 mol dm-, in CH,CI,; 1.67 dm3, 1.67 mol, 1.13 equiv.) were introduced into a flask under argon. The reaction was stirred for 30 h at room temperature.The solvent was then distilled off and acetic anhydride (2.5 dm3) and concentrated H2S04 (10 cm3) were added to the residue. The mixture was heated for 15 min at 120 "C and then ice (5 dm3) was introduced into the flask. The mixture was stirred for 30 min and then filtered and the residue was washed with water and methanol and purified by prepar- ative HPLC (Zorbax PRO 10-Silica gel, spherical, 10 m, 300 x 440 mm, hexane-AcOEt, 97: 3, 70 dm3 h-', 20-25 bar, 280 nm) to give unchanged compound 12 (283 g, 26%), mono- acetoxypentapentyloxytriphenylene(434 g, 39%) and diacetyl- oxytetrapentyloxytriphenylene(I 10 g, 10%). When working with 2.5 equiv. of 9-BrBBN monoacetoxypentapentyloxytri-phenylene (2073, diacetoxytetrapentyloxytriphenylene (30%) and triacetoxytripentyloxytriphenylene(5%) were isolated.For analytical data see ref. 1. Preparation of the trimethoxytripentyloxytriphenylenes 14a and 14b Compound 13a was alkylated following the previously reported method.', The residue was purified by silica gel chromato- graphy (CH,CI,-hexane, 3 :2) to give pure compound 14a (88 mg, 86%). Compound 13b has been alkylated by the same procedure. Compound 14a, R,(CH2CI,)0.50; mp 146 "C (Found: C, 75.0; H, 8.3. C36H4806 requires C, 74.97; H, 8.39%); 6,(200 MHz; CDCI,) 7.82 and 7.79 (6 H, 2 x s, ArH), 4.24 (6 H, t, J 6.8, OCH,), 4.09 (9 H, s, OCH,), 2.05-1.88 (6 H, m, OCH,CH,), 1.65-1.35 [12 H, m, O(CH,),(CH,),] and 0.96 (9 H. t, J 7.0, CH,).Compound 14b (non symmetric isomer), R,(CH,CI,) 0.4; mp 118 "C; v,,,(KBr)/cm~' 2870, 2950 and 2970 (CH arom.); 6,- (200 MHz; CDCI,) 7.83-7.78 (6 H, m, ArH), 4.24 (6 H, t, J6.8, OCH,), 4.09 (9 H, s, OCH,), 2.05-1.88 (6 H, m, OCH,CH,), 1.65-1.35 [I2 H, m, O(CH,),(CH,),] and 0.96 (9 H, t, J 7.0, CH,); m/z (EI) 576 (M', 100%).Preparation of non symmetric 2,6,1l-tris[(oct-ll-en-l -yl)- oxy] tripentyloxytriphenylene15 Compound 13b was alkylated by the previously reported method.', The residue was purified by silica gel chromato- graphy (CH,CI,-hexane, 1 :2 then I : 1) to give pure non sym- metric compound 15 (70 mg, 78%), R,(CH,CI,-hexane, 1 : I) 0.5; phase behaviour: c 29 "C Dh 47 "C (Found: C, 79.0; H, 9.4. C5,Hs406 requires C, 79.12; H, 9.78%; dH(200 MHz; CDCI,) 7.81 (6 H, s, ArH), 5.81 (3 H, tdd, J,,,,, 17.0, Jcis10.2 and J 6.6, CH,CH=CH,), 4.99 (3 H, d, J,,,,, 17.0, CH,CH=CH,), 4.93 (3 H, d, Jcis9.6, CH2CH=CH,), 4.21 (12 H, t, J 6.5, OCH,), 2.05-1.82 (1 8 H, m, CH,CH=CH, and OCH,CH,), I .65-1.35 [30 H, m, O(CH2)2(CH2)12 or 31] and 0.95 (9 H, t, J 7.0, CH,); m/: (EI) 866 (M', 100%).Prepamtbn of a mixture of tripkesyienes f6a, 168 and rec The cleavage of the methyl groups was achieved foflowing the previously described method. '*' Starting with compound 14a (0.88 g, 3.83 mmol), BuLi (2.5 equiv.) and diphenylphosphine (2.5 equiv.), the cleavage was achieved by refluxing the mixture for 30 min. The reaction was monitored by TLC. The crude reaction mixture was purified by silica gei chromatography.Only the fractions containing compound 16c were collected (CH,Cl,-hexane, 3 :2) to give a 16c enriched mixture (714 mg, -85%), R,(CH,Cl2) 16a 0.57,16b0.69 and 16c0.63;dH(16c,200 MHz; CDCl,) 7.92,7.81,7.78,7.75 and 7.74 (6 H, 5 x s, ArH), 5.90(1.4H, brs,0H),4.27and4.24(6H72x t, J7.1 and5.4, OCH,), 4.08 (3 H, s, OCH,), 2.05-1.85 (6 H, m, OCH,CH,), 1.65-1.35 C12 H, m, OCH,CH,(CH,),] and 0.97 and 0.96 [9 H, 2 x t, J 6.9 and 6.9, O(CH2),CH,], m/z (16c, EI) 548 (M+, 100%). Synthesis of Zmethoxy-6,lO-bis[ (oct-7-en-l-yl)oxy]- 3,7,1l-tripentyloxytriphenylene 17 A mixture of compounds 16a, 16b and 16c was alkylated following the previously reported method. l4 The residue was purified by silica gel chromatography (CH,Cl,-hexane, 1 :1) to give pure compound 17 (370 mg, 37%), R,(17) 0.72, R,(mono- olefin) 0.62, R,(triolefin) 0.80; mp 50 "C (Found: C, 78.0; H, 9.4.CS0H7,O6 requires C, 78.08; H, 9.44%); v,,,(KBr)/cm-' 2850 and 2950 (CH arom., olefin); dH(200 MHz; CDCl,) 7.85-7.75 (6 H, m, ArH), 5.81 (2 H, tdd, J,,,,, 17.0, Jcis10.2 and J 6.5, CH,CH=CH,), 4.98 (2 H, d, J,,,,, 17.0, CH,CH=CH,), 4.92 (2 H, d, Jcis10.2, CH,CH=CH2), 4.24 and 4.21 (10 H, 2 x t, J6.4, OCH,), 4.08 (3 H, s, OCH,), 2.15-1.85 (14 H, m, CH,CH=CH, and OCH,CH,), 1.65-1.35 [24 H, m, O(CH,),(CH,)[, or ,]] and 0.95 (9 H, t, J 7.0, CH,); m/z (EI) 768 (M', 100%). Synthesis of 2-hydroxy-6,10-bis[ (oct-7-en-l-yl)oxy]-3,7,11-tripent yloxytriphenylene 18 The cleavage of the methyl group was achieved following the previously described method.l1 Starting with compound 17 (0.388 g, 0.5 mmol), BuLi (1.4 equiv.) and diphenylphosphine (1.4 equiv.), the cleavage was completed by refluxing the mixture 1 h. The reaction was monitored by TLC [Aluminiumoxid 60 F254 type E, CH,Cl,-hexane, 3 :2, R,(17) 0.3, Rf(18) 0.01. The residue was purified by silica gel chromatography (CH,Cl,- hexane, 3 :2, R,0.4) to give the title compound (297 mg, 78%), mp 58 "C; v,,,(KBr)/cm-' 3550 (free OH), 3450 (bonded OH) and 2850 and 2950 (CH arom., olefin); dH(200 MHz; CDC1,) 7.94,7.8 1,7.80 and 7.75 (6 H, 4 x s, ArH), 5.89 (1 H, s, OH), 5.8 1 (2 H, tdd, J,,,,, 17.0, Jcis10.2 and J 6.6, CH,CH=CH,), 4.99 (2 H, d, J,,,,, 17.0, CH,CH=CH,), 4.93 (2 H, d, Jris10.0, CH,CH=CH,), 4.324.14 (10 H, m, OCH,), 2.15-1.82 (14 H, m, CH,CH=CH, and OCH,CH,) and 1.68-1.35 [24 H, m, O(CH,),(CH,)[, 0.96 (9 H,t, J 7-07 CH3); m/z (El) 754 or ,117 (M+, 100%).Synthesis of 2-[3-(methacryloyloxy)propoxy]-6,1O-bis-[(oct-7-en-l-yl)oxy]-3,7,11-tripentyloxytriphenylene 19 First, compound 18 was alkylated following the previously reported method.', The residue was purified by silica gel chromatography (CH,Cl,-AcOEt, 1 :0 then 19 :1) to give the pure intermediate (239 mg, 77%), R,(CH,Cl,-AcOEt, 19: 1) 0.65; mp 76.5 "C; v,,,(KBr)/cn-' 3400 (OH) and 2850 and 2940 (CH arom., olefin); dH(200 MHz; CDCl,) 7.81 and 7.78 (6 H, 2 x s, ArH), 5.81 (2 H, tdd, J,,,,, 17.0, Jcis10.2 and J 6.6, CH,CH=CH,), 4.99 (2 H, d, J,,,,, 17.3, CH,CH=CH,), 4.93 (2 H, d, Jcis10.3, CH,CH=CH,), 4.42 [2 H, t, J 5.7, OCH2- (CH,),OHJ, 4.21 [lo H, t, J6.3, OCH,(CH,)[, or sl], 3.96 (2 H, dt, J 5.7 and 5.7, CH,OH), 2.90 (1 H, s, OH), 2.25-1.87 [16 H, m, OCH,CH,CH,OH, CH,CH=CH, and OCH,CH,-(CH2)[2 or 4119 1*68-1*35 C24 H7 m7 O(CH,),(CH,)[, or 311 and 0.96 (9 H, t, J 6.9, CH,); m/z (EI) 812 (M+, 100%).This inter- mediate was acylated to provide 19 (see second step). Secondly, the intermediate triphenylene derivative (194 mg, 0.24mmol), diisopropylethylamine (0.22 cm3, 1.25 mmol), acryl- oyl chloride (0.12 cm3, 1.25 mmol) and 2,6-di-tert-butyl-p- J. CHEM. SOC. PERKIN TRANS. 1 1995 cresol(50 mg, 0.23 mmol) were added at 0 "C and under argon to CH,Cl, (2.5 cm3).The reaction was stirred 4 h at room temperature and then washed with aqueous K2C03. The organic phase was dried over MgSO,. The crude diacrylate was purified by silica gel chromatography (CH,Cl,-hexane 3 :2 then 1 :0) to give pure compound 19 (169 mg, 80%),R,(CH,CI,) 0.65; phase behaviour: c 51 "C (D,,43 "C) i (Found: C, 76.2; H, 9.1. C,,H8,O8 requires C, 76.33; H, 9.15%); v,,,(KBr)/cm-' 2860 and 2950 (CH arom., olefin) and 1725 (CO); dH(200 MHz; CDCl,) 7.84 and 7.81 (6 H, 2 x s, ArH), 6.1 1 [l H, s, OCOC-(CH,)=CH,], 5.81 (2 H, tdd, J,,, 17.0, Jcis10.2 and J 6.6, CH,CH=CH,), 5.54 [l H, s, OCOC(CH,)=CH,], 4.99 (2 H, d, J,,,,, 15.5, CH,CH=CH,), 4.93 (2 H, d, Jcis9.5, CH,CH=CH,), 4.45 [2 H, t, J 6.3, OCH,(CH,),OCO], 4.32 (2 H, t, J 6.2, CH,OCO), 4.21 [lo H, t, J 6.5, OCH,(CH,)I, or 511, 2.38-2.22 (2 H, m, OCH,CH,CH,O), 2.15-1.85 [17 H, m, OCOC-(CH,)=CH,, CH,CH=CH, and OCH,CH,(CH,)[, or ,]I, 1.68- 1.35 [24 H, m, O(CH,),(CH,)[, or ,,I and 0.95 (9 H, t, J 7.0, CH,CH,); m/z (EI) 881 (M', 100%).Synthesis of 2-(triisopropylsilyloxy)-3,6,7,10,1 l-penta-pentyloxytriphenylene 21 Compound 20 (0.5 g, 0.74 mmol), diisopropylethylamine (0.16 cm', 0.89 mmol) and triisopropylsilyl trifluoromethanesulfon- ate (0.26 cm3, 0.96 mmol) were added under argon to CH,Cl, (5 cm3). The reaction mixture was stirred for 1 h at room temperature and then washed with water. The organic phase was dried over MgS0,. The crude product was purified by silica gel chromatography (CH,Cl,-hexane, 1 :2 then 1 :1) to give pure compound 21 (0.615 g, loo%), Rf(CH,C1,-hexane, 1 :2) 0.27; mp 40OC; v,,,(KBr)/cm-' 2860 and 2950 (CH arom.); dH(200 MHz; CDCl,) 7.87, 7.80 and 7.74 (6 H, 3 x s, ArH), 4.284.12 (10 H, m, OCH,), 2.03-1.83 (10 H, m, OCH,CH,), 1.65-1.25 (23 H, m, O(CH,),(CH,), and Si[CH(CH,),],}, 1.16 (18 H, d, J 6.8, Si[CH(CH,),],} and 1.35-0.70 [33 H (including the doublet at 1.16), m, CH,CH,]; m/z (EI) 831 ([M + l]', 100%).Synthesis of dihydroxy-triisopropylsilyloxytripentyloxy-triphenylenes 22a, 22b, 2% and 22d Compound 21 (0.5 g, 0.6 mmol), CH,C12 (5 cm3) and 9-BrBBN (1 mol dmP3 in CH,Cl,; 1.5 cm3, 1.5 mmol, 2.5 equiv.), were introduced into a flask under argon. The reaction mixture was stirred for 30 h at room temperature and then was slowly quenched by the addition of 2-aminoethanol (0.1 cm3, 1.6 mmol).Water was added to the mixture and then it was extracted with CH,Cl,. The organic phase was dried over MgSO, and purified by silica gel chromatography (CH,Cl,- hexane, 1 :1 then 3: 2 then 1 :O). The column affords pure compound 22a (69 mg, 17%), pure compound 22d (137 mg, 33%) and a mixture of compounds 22b and 22c (114 mg, 27.5%). Compound 22a, R,(CH,Cl,-hexane, 3: 2) 0.14; mp 141 "C; dH(200 MHz; CDCl,) 7.91, 7.90, 7.84, 7.73, 7.71 and 7.69 (6 H, 6 x s, ArH), 5.86 and 5.84 (2 H, 2 x s, OH), 4.324.12 (6 H, m, OCH,), 2.05-1.88 (6 H, m, OCH,CH,), 1.65-1.25 (15 H, m, O(CH,),(CH,), and Si[CH(CH,),],}, 1.17 { 18 H, d, J 6.7, Si[CH(CH,),],} and 0.96 and 0.95 (9 H, 2 x t, J 6.8 and 6.8, CH,CH,); m/z(FD) 691 ([M + l]', 100%).Compounds 22b and 22c, R,(CH,Cl,-hexane, 3: 2) 0.61; dH-(200 MHz; CDCl,) 7.95-7.70 (6 H, m, ArH), 5.90-5.86 (2 H, m, OH), 4.32-4.10 (6 H, m, OCH,), 2.05-1.88 (6 H, m, OCH,CH,), 1.65-1.25 (15 H, m, O(CH,),(CH,), and Si[CH(CH,),],}, 1.16 and 1.15 { 18 H, 2 x d, J 6.7 and 6.7, Si[CH(CH,),],} and 0.96 and 0.95 (9 H, 2 x t, J 7.0 and 7.0, CH,CH,); m/z (FD) 691 ([M + l]+, 100%). J. CHEM. SOC. PERKIN TRANS. 1 1995 Compound 22d,R,(CH,Cl,-hexane, 3 :2) 0.54;mp 1 10 "C; 5 P. Henderson, H. Ringsdorf and P. Schuhmacher, Liq. Cryst., in the press. (LC 4.06/769) 6,(200 MHz; CDCl,) 7.95-7.68 (6 H, m,ArH), 5.89and 5.86 6 R. C. Borner and R. F. W. Jackson, J. Chem. SOC.,Chem. Commun., (2H,2 x s,0H),4.324.10(6H,m,0CH2),2.05-1.85(6H,m,1994,845.OCH,CH,), 1.65-1.25 (15 H, m, O(CH,),(CH,), and SiCCH- (CH3)J3), 1.17 (18 H, d, J6.6,Si[CH(CH,),],) and 1.00and 0.88 (9H, m,CH,CH,); m/z (FD) 691 ([M + 1]+, 100%).References 1 W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983,4,807; W. Kreuder, H. Ringsdorfand P. Tschirner, Makromol. Chem., Rapid Commun., 1985,6,367. 2 D. Adam, F. Closs, T. Frey, D. Funhoff, D. Haarer, H. Ringsdorf, P. Schuhmacher and K. Siemensmeyer, Phys. Rev. Lett., 1993, 70, 457; D. Adam, F. Closs, T. Frey, D. Funhoff, D. Haarer, H. Ringsdorf, P. Schuhmacher and K. Siemensmeyer, Ber. Bunsenges. Phys. Chem., 1993,97,1366; D. Adam, P. Schuhmacher, J. Simmerer, L. HauDling, K. Siemensmeyer, K. H. Etzbach, H.Ringsdorf and D. Haarer, Nature, 1994,371, 141. 3 C. Catry, M. Van der Auweraer, F. De Schryver, H. Bengs, L. HauDling, 0. Karthaus and H. Ringsdorf, Makromol. Chem., 1993, 194, 2985; M. Van der Auweraer, C. Catry, L. Feng Chi, 0.Karthaus, W. Knoll, H. Ringsdorf, M. Sawodny and C. Urban, Thin Solid Films, 1992, 210121 1, 39. 4 (a) N. C. Maliszewskyj, P. A. Heiney, J. Y. Josefowicz, J. P. McCauley, Jr. and A. B. Smith 111, Science, 1994, 264, 77; (b) M. Vandevyver, P.-A. Albouy, C. Mingotaud, J. Perez, A. Barraud, 0.Karthaus and H. Ringsdorf, Mol. Cryst. Liq. Cryst., 1993, 235, 51. 7 N. Boden, R. J. Bushby and A. N. Cammidge, J. Chem. SOC., Chem. Commun., 1994,465. 8 I. M. Matheson, 0.C. Musgrave and C. J. Webster, J. Chem. Soc., Chem. Commun., 1965,278; N. Boden, R. C. Borner, R. J. Bushby, A. N. Cammidge and M. V. Jesudason, Liq. Cryst., 1993,15, 851. 9 H. T. Nguyen, M. C. Bernaud, G. Sigaud and C. Destrade, Mol. Cryst. Liq. Cryst., 1981,65, 307. 10 J. W. Goodby, M. Hird, K. J. Toyne and T. Watson, J. Chem. Soc., Chem. Commun., 1994,1701. 11 R. E. Ireland and D. M. Walba, Org. Synth., Coll. Vol. VI, 1988,567; F. G. Mann and M. J. Pragnell, J. Chem. SOC., 1965,4120. 12 M. V. Bhatt, J. Organomet. Chem., 1978,156,221. 13 H. Bengs, H. Finkelmann, J. Kupfer, H. Ringsdorf and P. Schuhmacher, Makromol. Chem., Rapid Commun., 1993, 14, 445; J. Kupfer and H. Finkelmann, Makromol. Chem., Rapid Commun., 1991, 12, 717. 14 S. Bauer, H. Fischer and H. Ringsdorf, Angew. Chem., 1993, 105, 1658;Angew. Chem., Int. Ed. Engl., 1993,32, 1589. 15 S. Hanessian, T. J. Liak and B. Vnasse, Synthesis, 1981, 396. Paper 4/063921 Received 19th October 1994 Accepted 29th November 1994