o-Quinonoid compounds. Part XI.exo-Selectivity in the Dielsndash;Alder reactions of phenyl-substitutedo-quinonoid dienes

摘要

1654 J.C.S. Perkin Io-Quinonoid Compounds. Part X1.l exo-Selectivity in the Diels-AlderReactions of Phenyl-substituted o-Quinonoid DienesBy David W. Jones and Richard L. Wife, Organic Chemistry Department, The University, Leeds LS2 9JTButa-I ,3-diene, isoprene, cyclopenta-I ,3-diene, dimethyl maleate, norbornadiene, norbornene, cis- but-2-ene,and cyclopentene add to 1.4-diphenyI-2-benzopyran-3-one (2; R 1 = R2 = Ph) to give mostly exo-adducts;only for the addition of furan is the endo-adduct preferred. By comparison with the preferred endo-addition to2-benzopyran-3-one, its 1 -phenyl derivative (2; R1 = Ph, R2 = H), and 1,3-diphenylinden-2-one (15) theexo-selectivity in additions to (2; R1 = R2 = Ph) is attributed to inhibition of secondary interactions by non-coplanar phenyl substituents.1,4-DIPHENYL-2,3-NAPHTHOQUINONE (1) can be generatedas a reactive intermediate by low temperature oxidationof the corresponding catechol and trapped by a varietyof olefins and dienes.2 However the Diels-Alder reac-tions of (1) are exceptional in that in most cases theexo-adduct predominates.Although there are examplesof additions in which the exo-adduct predominates,5 orthe exo- and endo-adducts are formed in similar amounts,6there appears to be little correlation between structureand tendency to exo-addition. In search of such correl-ation, and precedent for the exo-additions to (l), westudied the additions of dienes and olefins to the isolablepyrone (2; R1 = R2 = Ph).lb Similar steric factorsshould operate in additions to (1) and (2; R1 = R2 =Ph) and both compounds would be expected to behave( 1 1 (2)as electron-deficient dienes in Diels-Alder reactionsproceeding with inverse electron demand.With isoprene in benzene at 130 "C the pyrone (2;R1 = R2 = Ph) gives the exo-adduct (3) (60y0), theertdo-adduct (4) (1374, and an adduct tentativelyformulated as (5) (10).The configurations of (3) and(4) as well as the orientation of addition are assigned on1 ( a ) Part X, D. W. Jones and G. Kneen, preceding paper;(b) preliminary communication, D. W. Jones and R. L. Wife,J.C.S. Chem. Comm., 1973, 421.a D. W. Jones and R. L. Wife, J.C.S. Perkin I , 1974, 1; for arelated observation see ref. 3.a D. W. Jones and R. L. Wife, J.C.S. Perkin I, 1972, 2722.4 J.Sauer, Angew. Chem. Internat. Edn., 1967, 6, 16.the basis of the reactions of (3) and (4) with trifluoro-acetic acid (20 "C). The exo-adduct (3) gives the lactone(6) (88) whereas the endo-adduct (4) gives the indane(7) (84). The spectroscopic properties of (6) and (7)(Experimental section) fully support the assignedstructures. In particular the coupling between H, andH, (6.5 Hz) strongly favours a cis-fusion of rings A and Bin both (6) and (7). Molecular models indicate that forthe rigid trans-isomers the dihedral angle between theseprotons is ca. 100" and therefore inconsistent with theobserved coupling constant. However in the moreflexible cis-isomers conformations with dihedral anglesas small as 30" are possible.The formation of (6) and(7) could involve acid-catalysed elimination of (3) and(4) to stereoisomeric acids (8) followed by protonation ofthe double bond see (S) to give stereoisomeric carbo-cations. In the stereoisomer from (3) neutralisation ofthe carbocation site by the cis-carboxy-group gives thelactone (6), but in the stereoisomer from (4) electro-philic attack of the carbocation on the cis-phenyl groupgives the indane acid (7). A similar sequence triggeredby protonation of the double bond in (3) and (4) is alsopossible.In the n.m.r. spectra of (3) and related exo-adducts thesignals for Ha and Hb appear at higher field (6 6.25-6.5and 6.5-6.8) than those of the other aromatic protons,6 ( a ) C. M. Anderson, I. W. McCay, and R. N.Warrener,Tetrahedron Letters, 1970, 2735; (b) M. A. Battiste and C. T.Sprouse, ibid., p. 4661; R. Breslow, G. Ryan, and J. T. Groves,J . Amer. Chem. SOC., 1970, 92, 988; (G) M. P. Cava and F. M.Scheel, J . Org. Chem., 1967, 52, 1304.6 ( a ) K. N. Houk, Tetrahedron Letters, 1970, 2621; (b) R. W.LaRochelle and B. M. Trost, Cham. Comm., 1970, 1353; P. J.Machin, A. E. A. Porter, and P. G. Sammes, J.C.S. Perkin I , 1973,404.7 J. M. Holland and D. W. Jones, J . Chem. SOC. ( C ) , 1970,5301976 1655presumably because both phenyl rings can adopt con- adduct predominated. This uniform exo preferenceformations like those shown in 9; N = H, X = provides good analogy for the exo-addition of dienes andMeC(:CH,) appropriate for shielding Ha and Hb. In the olefins to the putative reactive intermediate (1).There isendo-adduct 9; N = MeC(:CH,), X = HI the required also analogy for our ability to trap (1) with cis- but notconformation of one phenyl ring is destabilised by steric with trans-but-2-ene. When equal quantities of cis- andclash with the endo-substituent and only Hb is shielded trans-but-2-ene compete for (2; R1 = R2 = Ph) the(6 6.55-6.8). That the shielded protons are Ha and yield of exo,cis-adduct (11) is three times the combined1 xHb is supported by the spectrum of the exo-adductwhich shows signals for the shielded aromatic protons assinglets. Similar shielding effects were noted in theexo- and endo-adducts of (1) with butadiene where theconfigurations were established chemically.2 This n.m.r.criterion therefore constitutes a convenient and reliablemeans of establishing the endo- or exo-stereochemistry ofadducts derived from (2; R1 = R2 = Ph).It has beenused extensivelyin the present work. For some examplesother n.m.r. evidence further supports the validity of themethod. For the endo-norbornadiene adduct the signalsfor the methylene protons appear at much higher fieldthan for the exo-adduct (Experimental section), andfor the furan adducts similar though smaller shieldingof endo-groups by the phenylene ring provides a checkon the assignments based on the shielding of Ha and Hb.Furthermore for all the adduct pairs described in thisand the preceding paper l a derived from simple olefinsand dienes the exo-adduct has the greater mobility onsilica chromatography. In contrast the endo-adduct hasthe greater RF value when the adducts are derived froman oxygen-containing olefin (furan or dimethyl maleate).By the joint use of these criteria, configurations wereassigned to the adducts from (2; R1 = R2 = Ph) and thefollowing dienophiles : dimethyl maleate, buta-l,3-diene,cyclopenta-l,3-diene, cyclopentene, cis-but-2-ene, nor-yield of the trans-adducts (12) and (13).More rapidreaction of cis- than of trans-but-2-ene with (2; R1 =R2 = Ph) contrasts with more rapid reaction of the samediene with dimethyl fumarate than with dimethylPh ,R3 Phm o Ph(15)(11) R'= R2 = Me, R3 = R' z H(12) R' = R3 = Me, R2 = RZ = H(13) R' R3 = H,(14) R' = R3 = COzMe.R2 = RZ =H(22) R1 = R2 = C02Me, R3 = R' =H amp;:. (23) R' = R2 = H,R2 = RZ = MeR3 = RL = C02 MeA 4 t l 'bsol; 0Ph(16)maleate. The latter result is that expected for conjugateddienophiles.* Whereas the trans-adducts (12) and (13)are formed in similar amounts the fumarate adduct (14)is the major product. Similar behaviour is found forcorresponding additions to the unsubstituted pyrone(2; R1 = R2 = H).l7* exo-Selectivity is associatedbornadiene, and norbornene. In all cases the exo- 8 J. M. Holland and D. W. Jones, J . Chem. SOC. (C), 1970,5361656 J.C.S. Perkin Iwith the presence of phenyl substituents as relatedadditions to the pyrone (2; R1 = R2 = H) are endo-selective.la Whereas (2; R1 = R2 = Ph) reacts withdimethyl maleate to give more exo-adduct (58) thanendo-adduct (25), the diene (2; R1 = Ph, R2 = H)gives more edo-adduct (53) than exo- (9).It isknown that (2; R1 = R2 = H) gives only the endo-adduct with dimethyl maleate.8 Phenyl substituents donot noticeably inhibit endo-addition to the five-memberedring diene system in 1,3-diphenylinden-2-0ne (15), whichgives mainly endo-adducts with dimethyl maleate andcycl~pentadiene.~ In the present work we have shownthat this endo-preference extends to cyclopentene,butadiene, and norbornadiene. It is likely thereforethat the phenyl groups inhibit endo-addition by a stericrather than an electronic effect. Greater coplanarity ofthe phenyl substituents and the diene system should bepossible in (15) than in (16). In the latter, steric inter-actions of the type shown prevent full coplanarity. Theortho-hydrogen atoms of non-coplanar phenyl groups willnormally favour endo-addition.1'actions are reduced the exo-adduct may be favoured bysteric effects.Thus in the enzdo-transition state (17) threeto occupy more sterically demanding environments thanin the exo-transition state (18). In agreement theexo-preference in addition to (2; R1 = R2 = Ph)decreases with the effective size of the olefin substituents.For cis-but-2-ene and cyclopentene only the exo-adductsare isolated. For cyclopentadiene the exo : endo ratio is4 : 1; for norbornadiene it is 1.5 : 1; for furan the endo-adduct predominates ; and for cyclopropene only theemlo-adduct is reported.1deg; For the norbornadieneaddition steric interactions with the C-3 and C-5 hydrogenatoms would be diminished.This trend will continuefor the furan addition, and for the cyclopropene additioninteraction of this type will be absent. The C-4 hydrogenatom interacts mainly with the diene system and this maythe exo-i~omer.~ Related effects may destabilise theendo-transition states in additions to 1,2-diphenylbuta-diene l2 and the 3,4-diphenylcyclopentadienone (19).5aThe latter gives mostly exo-adducts with certain cyclo-butenes and steric destabilisation of the endo-transitionstates has been proposed as an e~planation.~" In agree-m wLcbsol;/vw vvvvv(17 1 (18)shield C-4a and C-8a and so impede the interactions which P hWhen such inter- phMemethylene hydrogen atoms of cyclopentene (0) appear (1 9 1 ( 2 0 I ( 2 1 )ment we find that addition of the effectively smallernorbornadiene to (19) gives only the endo-adduct (20) ,l3The configuration of (20) is supported by the appearanceof the AB system for the methylene protons at verysimilar 6 values in (20) and in the alcohol obtained byreduction with lithium aluminium hydride. That addi-tions to (19) are subject to steric control owing to non-coplanarity of the phenyl groups and the diene systemis indicated by the greater ertdo-selectivity observed inadditions to (21).14 These observations are of someimportance as the diene (19) has been used to test fordiene-alkyl group interactions 6a~15 and the results havebeen used to contest the conclusions of others.l6well be a favourable attractive interaction.la EXPERIMENTALPhenY1 to Promoteselectivity in the addition of norbornadiene to For general details see the preceding papr.laAdditions to 1,4-DiphenyZ-2-benzopyra~~-3-one.--(a) Di- 1~3-diphenylbenzoclfuran.This gives Only the exO- methyl fumarate (155 mg), acetic anhydride (5 ml), and thea d d ~ c t , ~ ~ whereas addition of norbornadiene to benzo- title compound (80 nig) were boiled under reflux in a nitro-clfuran itself gives exo- and endo-adducts in the ratio ca. gen atmosphere (2.6 h). Removal of solvent and the1.8 : 1. This could indicate lack of complete coplanarity excess of dienophile under high vacuum at 100 "C gave aof the phenyl groups with this five-membered ring diene crude product that crystallised from benzene to give thesystem.Nevertheless addition of cyclopentene to 1,3- d i k t (14) (1,2,3,4-tetrahydro-2,3-bisnzethoxycarbonyZ- 1,4-diphenylbenzocfuran is strongly endo-selective. The di~~en~zna~hthazene~l~~~car~ozactone~ (85 mg, T2) , m*p*182.5-184.5" (from methanol) (Found: C, 73.35; H, 5.2. major adduct obtained by Wittig and Burger l1 has the C,,H,,O, requires C, 73.3; H, 5.2), v,, 1 775, 1 770, endo-configuration, for it is prepared by catalytic reduc- 6oo, 180, and 15. cm-l, ,.85--7.1configuration of which rests on n.m.r. comparison with (1 H, d, J 6 H ~ ) , and 3-62 (6 H, s); m/e 411 (m - OMe),lo R. E. Moerck andM. A. Battiste, J.C.S. Chem. Comm., 1972,l1 G. Wittig and T. F. Burger, Annalen, 1960, 632, 85.l2 P.C. Jain, Y . N. Mukerjee, and N. Anand, J . Amer. Chem.l3 Cf. K. Mackenzie, J . Chem. SOC., 1960, 473.,43,tion Of the corresponding cyclopentadiene adduct, the (13 H, m), 6.65-6.35 (1 H, m), 3.84 (1 H, d, J 6 Hz), 3-64398, 3M9, 366, 338~ and 307 4*6j 4*1, 157 43, and loo* 9 J. amp;I. Holland and D. W. Jones, J . Chem. SOG. (C), 1971, 608.14 D. W. Jones, J.G.S. Chem. Comm., 1975, 199.l6 K. N. Houk and L. J. Luskus, J . Amer. Chem. SOC., 1971, 93,4606.l6 Y. Kobuke, T. Fueno, and J. Furukawa J . Amer. Chem.SOC., 1970,92, 6548; Y . Kobuke, T. Sugimoto, J. Furukawa, andT. Fueno, ibid., 1972, 94, 3633.1171.SOC., 1974, 96, 29961976(b) Dimethyl maleate (2 ml), acetic anhydride (5 ml), andthe title compound (200 mg) were boiled under reflux undernitrogen (16 h).The crude product obtained by evapor-ation at 100 "C in high vacuum crystallised from benzene togive the exo-adduct (22) (132 mg, 45), m.p. 264-267'(from benzene-petroleum) (Found: C, 73.1; H, 5.l),vmX. 1777, 1600, 1585, 1215, 1 140, 767, and 698 cm-l,6 7.9-7.0 (12 H, m), 6.9-6.6 (1 H, m), 6.6-6.35 (1 H, m),4 and 3.98 (2 H, inner lines of AB system), 3.56 (3 H, s),and 3.4 (3 H, s); m/e 411 (M - OMe), 398 (M - CO,),379, 366, 338, and 307 (0.9, 2.4, 2.6, 13.5, 50, and 100).The mother liquor (145 mg) was chromatographed on silica(35 g). Elution with benzene-ether (19 : 1) afforded thefumarate adduct (14) (30 mg, lo), identical with thecompound described in (a) (mixed m.p. and n.m.r. and i.r.spectra).Continued elution gave the endo-adduct (23)(39 mg, 13y0), m.p. 216-218" (from benzene-petroleum)(Found: 73.6; H, 5.15), vmX. 1 768, 1 760, 1 757, 1 730,1 605, 1 210, 1 017, 972, 750, and 703 cm-1, 6 7.8-7.2 (l4H,m), 4.25 (2 H, apparent s), 3.54 (3 H, s), and 3.47 (3 H, s);m/e 411, 398, 396, 365, 338, and 307 (2.3, 15, 28, 38, 65, and100). The dimethyl maleate used in this experimentcontained a small amount ((0.5 by g.1.c.) of dimethylfumarate. The experiment was therefore repeated withdimethyl maleate freed of the fumarate ester by preparativeg.1.c. lJ4-Dipheny1-2-benzopyran-3-one (100 mg) and di-methyl maleate (250 mg) in acetic anhydride (5 ml) wereboiled under reflux (40 h). After removal of solvent andthe excess of dienophile the n.m.r.spectrum of the crudeproduct indicated the presence of the exo-adduct (22) (58),the endo-adduct (23) (25), and the fumarate adduct (14)(2.8). Dimethyl maleate was not isomerised to thefumarate ester under the reaction conditions (n.m.r.).The reaction of pure dimethyl maleate with 1,4-diphenyl-2-benzopyran-3-one in refluxing xylene (22 h) under nitrogengave a small amount of the fumarate adduct (14) (t.1.c.).(c) Buta-lJ3-diene (1 ml), benzene (5 ml), and the titlecompound (200 mg) were heated in a bomb immersed in anoil-bath at 130 "C (19 h). Chromatography of the producton silica in benzene gave the exo-adduct (24) (100 mg, 43),m.p. 146-149' (from benzene-petroleum) (Found: C,85.35; H, 5.7. C,,H,,O, requires C, 85.3; H, 5.7), vm,1740, 1635, 1600, 1180, 915, 760, 740, and 700 cm-l,6 7.8-7.25 (10 H, m), 7.25-6.9 (2 H, m), 6.8-6.5 (1 H, m),6.5-6.25 (1 H, m), 6.15-5.5 (1 H, m, vinyl), 5.354.95(2 H, m, vinyl), 3.65-3.2 (1 H, m, allylic), 2.88 (1 H, dd,J 13 and 10 Hz), and 2.4 (1 H, dd, J 13 and 5 Hz); m/e352 (M+), 308 (M - CO,), 298 (M - C,H,), 280, and 270(3.7, 29, 43, 15, and 100Yo).Further elution gave the endo-adduct (25) (39 nig, 17),m.p. 230-232' (from benzene-petroleum) (Found : C,85.35; H, 5.7), vmx 1745, 1 645, 1600, 1210, 740, and715 cm-l, 6 7.9-7.1 (13 H, m), 6.85-6.6 (1 H, m), 5.3-5.05 (3 K, m, vinyl), 4.0-3.5 (1 H, m, allylic), 3.04 (1 H, dd,J 13.5 and 10 Hz), and 2.17 (1 H, dd, J 13.5 and 3 Hz); m/e352, 308, 298, 280, and 270 (5, 100, 18, 46, and 76).(d) Isoprene (6 ml), benzene (15 ml), and 1,4-diphenyl-2-benzopyran-3-one (400 mg) were heated in a bomb immersedin an oil-bath a t 130 "C (19 h).Chromatography of theproduct on silica in benzene gave the exo-adduct (3) (295mg, 60) , m.p. 139-141" (from benzene-petroleum)(Found: C, 85.2; H, 5.8. C,,H2,0, requires C, 85.3; H,6.0), vmaX 1750, 1 740, 1640, 1595, 1 175, and 700 cm-1,6 7.9-7.25 (10 H, m), 7.25-6.9 (2 H, m), 6.8-6.5 (1 H, m),6.5-6.25 (1 H, m), 4 . 9 4 . 7 5 (2 H, m, vinyl), 3.37 (1 H, dd,J 10 and 6.5 Hz, allylic), 2.91 (1 H, dd, J 13 and 10 Hz,methylene), 2.36 (1 H, dd, J 13 and 6.5 Hz, methylene),and 1.66 (3 H, t , J 1 Hz, CHJ; m/e 366 (M'), 348(M - H,O), 322 (M - CO,), 305, 290, 280, and 270 (8.7,0.7, 5.8, 3.3, 32, 100, and 54).Further elution gave theexo-adduct isomer (5) (47 mg, lo), m.p. 183-184" (frombenzene-petroleum) (Found: C, 85.15; H, 6.1) , v-1 745, 1 630, 1600, 1 192, 1003, 752, 747, and 706 cm-l,6 7.9-6.9 (12 H, m), 6.85-6.5 (2 H, m), 6.0-4.7 (3 H,ABX system, vinyl), 2.56 (1 H, d, J 5 Hz, CH,), 2.47 (1 H,d, J 5 Hz, CH,), and 1.68 (3 H, s, Me); m/e 366, 351, 348,333, 321, 311, 305, 298, 294, 291, and 270 (15.4, 1.0, 1.8,0.77, 15.4, 6.3, 10.6, 71, 9.6, 8.3, and looyo).Continued elution of the column gave the endo-adduct (4)(64 mg, 13), m.p. 229-232" (from benzene-petroleum)(Found: C, 85.0; H, 6.0), v,, 1745, 1640, 1600, 1 200,745, and 700 cm-1, 6 7.8-7 (13 H, m), 6.8-6.56 (1 H, m),4.85-4.68 (2 H, m, vinyl), 3.65 (1 H, dd, J 10.5 and 5.0Hz, allylic), 3.05 (1 H, dd, J 13.5 and 10.5 Hz, CH,), and2.15 (1 H, dd, J 13.5 and 5 Hz, CH,); m/e 366, 348, 320, 305,289, 280, 276, and 270 (1.5, 0.6, 53, 100, 27, 13, 13, and 9).(e) Cyclopenta-l,3-diene (0.25 ml), benzene (5 ml), andl,P-diphenyl-2-benzopyran-3-one (80 mg) were set aside inthe dark (8 h).Chromatography of the product in benzene-ether (24 : 1) gave first the exo-adduct (80 mg), m.p. 257-261" (from chloroform-ethanol) (Found: C, 85.5; H, 5.75.C2,H2,02 requires C, 85.7; H, 5.5), vmx. 1740 and 1750cm-1, 6 8.0-7.3 (10 H, m), 7.3-7.0 (2 H, m), 6.72-6.52(1 H, m), 6.52-6.28 (1 H, m), 5.84 (2 H, m, olefinic),4.2-3.9 (1 H, m, allylic methine), 3.7-3.22 (1 H, m, meth-ine), and 2.71-2.38 (2 H, m, CH,). Continued elutiongave the endo-adduct (20 mg), m.p.227-231" (decomp.)(from chlorofonn-ethanol) (Found: C, 85.9; H, 5.65),vmx. 1 745 cm-l, 6 (9OMHz) 7.77-7.31 (10 H, m), 7.31-7.12(2 H, m), 7.12-6.94 (1 H, m), 6.94-6.81 (1 H, m), 5.55(1 H, m, olefinic), 5.34 (1 H, m, olefinic), 4.29 (1 H, dquint,J 9 and ca. 2 Hz, allylic methine), 3.86 (1 H, td, J 9 and4 Hz, methine), 2.84 (1 H, ddq, J 17, 9, and 2 Hz) , and 1.95(1 H, dm, J 17 and GU. 1.5 Hz).(f) Cyclopentene (2 ml) , benzene (8 ml) , and 1 ,Cdiphenyl-2-benzopyran-3-one (75 mg) were kept in the dark (48 h).The n.m.r. spectrum (ZHJpyridine) of the crude productobtained by evaporation under reduced pressure showed thepresence of only one adduct. Crystallisation from methyl-ene chloride-methanol gave the exo-adduct (76 mg, 82y0),m.p.254-257' (Found: C, 85.0; H, 6.2. C2amp;202requires C, 85.1; H, 6.1), vmx. 1 745, 1 600, 975, 755, and700 cm-l, 6 8.0-7.3 (10 H, m), 7.25-6.9 (2 H, m), 6.8-6.6 (1 H, m), 6.6-6.4 (1 H, m), 3.3-2.9 (2 H, m, methine),2.25-1.2 (6 H, m, CH,).(g) cis-But-2-ene (1.8 ml), trans-but-2-ene (1.8 ml),benzene (6 ml) , and 1 ,Pdipheny1-2-benzopyran-3-one(100 mg) were kept in a sealed bomb (15 days). Chromato-graphy of the product on silica in benzene gave first theexo,cis-adduct (11) (60 mg), m.p. 225-228" (from chloro-form-ethanol) (Found: C, 84.65; H, 6.35. CZ5H,,O2requires C, 84.7; H, 6.3), vmk 1745 cm-l, 6 8.0-7.28(10 H, m), 6.9-7.28 (2 H, m), 6.9-6.55 (1 H, m), 6.45-6.13 (1 H, m), 3.2-2.6 (2 H, m, methine), 0.96 (3 H, d,J 7 Hz), and 1.13 (3 H, d, J 7 Hz).Continued elutiongave the trans-adduct (12) (11 mg), m.p. 202-204' (fromchlorofonn-ethanol) (Found: C, 84.8; H, 6.2y0), vmaX1735 and 1745 cm-l, 6 7.91-7.29 (10 H, m), 7.25-7.0(3 H, m), 6.18-6.44 (1 H, m), 2.9-2.39 (1 H, m, methine),2.39-1.9 (1 H, m, methine), 1.28 (3 H, d, J 7 Hz), and 0.91658 J.C.S. Perkin I(3 H, d, J 7 Hz) : then the trans-adduct (13) (1 1 mg), m.p.185-187" (from chloroform-ethanol) (Found: C, 84.8;H, 6.2), vmaX 1 755 cm-l, 6 7.86-7.32 (10 H, m), 7.32-7.0(3 H, m), 6.9-6.6 (1 H, m), 2.95-2.4 (1 H, m, methine),2.4-1.79 (1 H, m, methine), 1.08 (3 H, d, J 7 Hz), and 0.87(3 H, d, J 7 Hz) . Further elution gave o-dibenzoylbenzene(8 mg) and 1,4-diphenyl-2-benzopyran-3-one (6 mg).The separate reactions of cis- and trans-but-2-ene with1,4-diphenyl-2-benzopyran-3-one gave the cis-adduct (1 1) ,and a mixture of the trans-adducts ( 12) and (1 3), respectively.(h) Norborna-2,5-diene (0.5 g), benzene (5 ml), and 1,4-diphenyl-2-benzopyran-3-one were kept in the dark (18 h) .Chromatography of the product on silica in benzene gavethe exo-adduct (60 mg), m.p.236-239" (from chloroform-ethanol) (Found: C, 86.15; H, 5.7. C28H2202 requiresC, 86.1; H, 5.7), vmax. 1 750 cm-l, 6 7.85-7.3 (10 H, m),6.84-7.3 (2 H, m), 6.6-6.84 (1 H, m), 6.25-6.6 (3 H, m,overlapping, olefinic and aromatic H), 3.09br (1 H, s),2.98-2.5 (3 H, m), 2.24br (1 H, d, J 10.5 Hz, CH,), and 1.3(1 H, d, J 10.5 Hz, CH,). Continued elution gave theendo-adduct (42 mg), m.p. 195-198" (decomp,) (from chloro-form-ethanol) (Found: C, 86.25; H, 5.75), vmx.1748cm-l, 6 8.0-7.34 (10 H, m), 7.3P-6.9 (4 H, m), 6.7-6.2(2 H, m, olefinic), 2.8-3.2 (4 H, m, methine), 0.71br (1 H, d,J 10 Hz, CH,), and -0.55br (1 H, d, J 10 Hz, CH,).(i) Norborn-2-ene (0.5 g) and 1,4-dipheny1-2-benzopyran-one (100 mg) were treated as described in (h) . Chromato-graphy of the product on silica in benzene-ether (24 : 1) gavethe exo-adduct (100 mg), ni.p. 250-252" (from chloroform-ethanol) (Found: C, 85.75; H, 6.15. C,,H,,O, requires C,85.7; H, 6.2y0), vmaX. 1 743 cm-l, 6 7.8-7.3 (10 H, m),7.25-6.98 (2 H, m), 6.8-6.5 (1 H, m), 6.5-6.25 (1 H, m),2.8-2.32 (2 H, m), 2.32-1.82 (2 H, m), 1.82-1.09 (5 H, m),and 0.9 (1 H, d, J 10.5 Hz, CH,).Continued elution gavethe endo-adduct (34 mg), m.p. 250-255" (decomp.) (fromchloroform-ethanol) (Found: C, 85.7; H, 6.0), vmax.1 740 cni-l, 6 8.0-7.35 (10 H, m), 6.9-7.35 (4 H, m), 3.0and 2.81 (2 H, AB system, J 8 Hz), 2.38br (2 H, s, bridge-head methine), 1.73-1.21 (4 H, m), 0.35br (1 H, d, J 10 Hz),and -0.82br (1 H, d, J 10 Hz).( j ) Furan (2.5 ml), benzene (5 ml), and 1,4-diphenyl-2-benzopyran-3-one (100 mg) were kept in the dark (3 weeks),and the product was chromatographed on silica in benzene-ether (97.5 : 2.5) to give first the endo-adduct (64 mg), m.p.250-254" (decomp.) (from chloroform-ethanol) (Found :C, 82.3; H, 4.7. C2,Hl8O3 requires C, 82.0; H, 4.95),vmax. 1 750 cm-l, 6 6.7-8.0 (14 13, m, aromatic), 5.91 (1 H,dd, J 3 and 2 Hz, vinyl HCO), 5.66 (1 H, d, J 10 Hz, HCO),4.85 (1 H, dd, J 3 and 2 Hz, vinyl HC-CO), and 4.45 (1 H,dt, J 10 and 2 Hz, HCCO) ; then the exo-adduct (9 mg), m.p.242-243" (from benzene-petroleum) (Found : C , 82.15 ;H, 5.05y0), vmax.1 757 cm-l, 6 (90 MHz), 7.41 (10 H, m),7.08 (2 H, ni), 6.66 (1 H, m), 6.41 (2 H, m, aromatic andvinylic HCO), 5.41 (1 H, d, J 9.75 Hz, HCO), 4.95br (1 H, s,vinylic HCCO), and 4.25br (1 H, d, J 9.75 and 1.5 Hz).Reaction of the Adduct (3) with Trifluoroacetic Acid.-Theexo-adduct (3) (20 mg) was kept in trifluoroacetic acid (0.5ml) (15.3 h). The product was diluted with water (20 ml)and extracted into methylene chloride (100 ml). Theextracts were washed with saturated sodium hydrogencarbonate solution and water, dried (MgSO,), and evaporatedto give 3a, 9b-dihyd~o-3,3-dimethyl-5,9b-di~henylnaj5htho 1,2-c furan-l(3H)-one (6) (17.5 mg, 88), m.p.195-196" (frombenzene-petroleum) (Found : C, 85.4; H, 5.9. C,,H,,O,requires C, 85.3; H, 6.0y0), v,, 1 750, 1 260, and 700 cm-l,vmx (CHCI,) 1 760 cm-l, A,, 231, 262sh, 264, and 272sh nm(E 22 100, 6 050, 6 525, and G 450), 6 7.9-7.6 (1 H, m),7.5-6.9 (13 H, m), 5.72 (1 H, d, J 6.5 Hz, vinyl), 3.3 (1 H,d, J 6.5 Hz), 1.6 (3 H, s, Me), and 1.26 (3 H, s, Me); m/e366 (M'), 322 (M - CO,), 320 (M - CH,O,), 307, 291, and280 (M - C4H602) (1.5, 0.75, 0.33, 1.1, 1.2, and 100).Reaction of the Adduct (4) with Trifiuoroacetic Acid.-Theendo-adduct (4) (60 mg) was set aside with trifluoroaceticacid (5 ml) (15.3 h) and the product worked up as describedabove. Acidification of the sodium hydrogen carbonateextract gave 7,l lb-dihydro-7,7-dimethyl-5-phenyl-6aH-benzocfluoreute-1 lb-carboxylic acid (7) (50 mg, 84), m.p.251-259" (from benzene-petroleum) (Found : C, 85.05 ;H, 6.0), v,,, 2 600-2 400, 1 700, and 1 690 cm-1, hx230, 259sh, 265, and 272 nm (c 24 600, 5 245, 6 370, and6 710), 6 10.93-10.53br (1 H, s, exch.D,O), 7.95-7.7 (1 H,m), 7.6-6.85 (12 H, m), 6.05 (1 H, d, J 6.5 Hz, vinyl),3.6 (1 H, d, J 6.5 Hz), 1.45 (3 H, s, Me), and 0.8 (3 H, s, Me);mle 366 (M'), 348 (M - H,O), 338 (M - CO), 333,320,305,and 291 (39, 10, 2, 8.5, 100, 52, and 50).Addition of l-Phenyl-2-benzopyran-3-one to DimethylMaleate.-Dimethyl maleate (260 mg) , o-benzoylphenyl-acetic acid (200 mg), and acetic anhydride (5 ml) wereboiled under reflux in a nitrogen atmosphere (4 h).Thesolvent and the excess of dienophile were removed a t 100 "Cin high vacuum and the residue was chromatographed onsilica in benzene-ether (9 : 1) to give the endo-adduct(173 mg, 53)' m.p. 141-142" (from benzene-petroleum)(Found: C, 69.15; H, 4.9. C21H1806 requires C, 68.9; H,4.9), v,, 1775, 1750, 1740, 1225, and 985 cm-1, 67.8-6.95 (9 H, m), 4.36 (1 H, d, J 2 Hz, HC-CO-0), 4.08(1 H, d, J 11 Hz, methine), 3.66 (1 H, dd, J 11 and 2 Hz,methine), 3.56 (3 H, s), and 3.5 (3 H, s ) ; m/e 366 (M+), 334,322, 320, 306, 289, 275, and 262 (1.8, 12.5, 6.5, 10, 4.3, 100,16, and 22.5). Continued elution gave the exo-adduct(30 mg, 9), m.p.135-137 and 160-162" (from benzene-petroleum) (Found: C , 68.85; H, 5.1), v,, 1 775, 1 760,1 740, and 1 230 cm-l, 6 7.8-7.0 (8 H, ni), 6.9-6.65 (1 H, m) ,4.42 (1 H, d, J 1.5 Hz, HC*CO*O), 3.83 (1 H, d, J 11 Hz,methine), 3.2 (1 H, dd, J 11 and 1.5 Hz, methine), 3.72(3 H, s), and 3.38 (3 H, s); m/e 366, 324, 321, 293, 289, 263,and 262 (6.7, 25, 50, 82, 6.4, 99, and 100).Additzon of Buta-1 , 3-diene to 1,3-Diphenylinden-2-one.-1,3-Dibromo- 1,3-diphenylindan-2-0ne (600 mg) , sodiumiodide (1.16 g), and butadiene (12 ml) in acetone (30 ml)were heated under nitrogen in a bomb immersed in an oil-bath a t 60-70 "C (8 h). The product was diluted withmethylene chloride, and washed with sodium thiosulphatesolution and water. Evaporation of the dried (MgSO,)solution and chromatography of the residue on silica inbenzene gave the endo-adduct (123 mg, 75), m.p.170-172"(from methanol) (Found: C, 89.0; H, 6.2. C,,H,,Orequires C, 89.25; H, 6.0y0), vmx 1770, 1645, 930, 750,740, and 700 cm-l, 6 7.6-6.7 (14 H, m), 5.45-5.0 (3 H, m,vinyl), 4.0-3.5 (1 H, m, allylic), 3.0 (1 H, dd, J 12 and 10Hz, CH,), and 1.75 (1 H, dd, J 12 and 5 Hz, CH,) ; m/e 336(M+), 308 (M - CO), 293, 280, 267, and 252 (3, 100, 13, 35,55, and 20).The earlier fractions from the column were impure;purification was achieved by chromatography on silica inbenzene-petroleum (3 : 7) which gave the exo-adduct (10nig, 2.3) as a gum (Found: M+, 336.152. C,SH,,Orequires M , 336.151), v,,.(film) 1 770, 1 645, 1 610, and 700cm-1, 6 7.73-7.1 (12 H, m), 6.9-6.72 (2 H, m), 5.95-5.45 (1 H, m, vinyl), 5.22-4.95 (2 H, m, vinyl), 3.2G2.81976 1659(1 H, m, allylic), and 2.49 and 2.4 (2 H, s and d, J 1 Hz,deceptively simple AB part of ABX system).Addition of Cyclopentene to 1,3-Diphenylinden-2-one.-The 1,3-diphenylinden-2-one dimer (1 10 mg), cyclo-pentene (1.5 ml), and xylene (6 ml) were heated in a bombplaced in an oil-bath at 156 "C (18 h).Evaporation of theproduct and chromatography of the residue on silica inbenzene gave the exo-adduct (30 mg), m.p. 124-127" (frombenzene-petroleum) (Found: C, 88.9; H, 6.45. C,,H,,Orequires C , 89.1; H, 6.3), vmx. 1 770, 1 605, 1 598, and1 580 cm-l, S 8.0-7.25 (10 H, m), 7.25-6.88 (2 H, m),6.88-6.54 (2 H, m), 3.04-2.7 (2 H, m, methine), and 2.5-0.8 (6 H, complex resonance, CH,).Continued elutiongave the endo-adduct (77 mg), m.p. 190-192" (from benzene-petroleum) (Found: C, 89.4; H, 6.45y0), vmaX 1 770, 1 760,1601, and 1580 cm-l, 6 7.3-7.5 (10 H, m), 7.3-7.0 (2 H,m), 7.0-6.7 (2 H, m), 3.5-3.11 (2 H, m, methine), 2.39-1.66 (2 H, complex m, CH,), and 1.66-0.5 (4 H, complex m,Addition of Norborna-2,5-diene to 1,3-Diphenylinden-2-one.-The l,S-diphenylinden-2-one dimer (60 mg), norborna-diene (2 ml) , and xylene (3 ml) were heated in a bomb placedin an oil-bath at 150 "C ( 5 h). Evaporation of the productand chromatography on silica in benzene gave the endo-adduct (70 mg), m.p. 183-185" (from chloroform+thanol)(Found: C, 89.7; H, 5.85. C,,H2,0 requires C, 89.8; H,5.9), vmaX.1 780, 1 604, and 1 582 cm-l, 6 7.65-7.3 (10 H,m), 7.3-7.05 (2 H, m), 6.98-6.65 (2 H, m), 6.38 (2 H, m,olefinic), 3.0 (2 H, m, bridgehead methine), 2.79br (2 H, s,methine), 0.66br (1 H, d, J 10 Hz, CH,), and -0.62br (1 H,d, J 10 Hz, CH,).Reduction of the Norbornadiene-l,3-Diphenylinden-2-oneAdduct.-To the foregoing adduct (50 mg) in ether (10 ml),lithium aluminium hydride (100 mg) was added, and themixture was boiled under reflux for 1.5 h. Water was addeddropwise to the product until the colour changed from greyt o white and the mixture was then boiled under reflux for 1 h.The product was filtered off and the filter-pad washedthoroughly with ether. The combined filtrate and washingswere dried (MgSO,) and evaporated to give the alcohol(45 rng), m.p.223-225" (from chloroform-ethanol) (Found :C, 89.5; H, 6.5. C,,H,,O requires C, 89.3; H, 6.4),( 3 3 2 ) .v,, 3 560, 3 460, 1 600, and 1 114 cm-1, 8 (CDC1,-D,O)7.7-7.22(lOH,m),7.22-6.95(2H,m),6.95-6.6(2H,m),6.35br (2 H, s, olefinic), 4.47 (1 H, s, HCO), 3.05 (2 H, s,methine), 2.66br (2 H, s, bridgehead methine), 0.65 (1 H,d, J 10 Hz, CH,), and -0.86 (1 H, d, J 10 Hz, CH,). In theabsence of D,O the OH resonance appeared at 1.88br (s) andthe singlet at 4.47 was broadened.Addition of Norborna-2,5-diene to 2,5-Dirnethyl-3,4-diphenylcyclopenta-2,4-dienone.-The 2,5-dimethyl-3,4-di-phenylcyclopenta-2,4-dienone dimer ( 100 mg) , norborna-2,5-diene (1 ml), and toluene ( 5 ml) were boiled under refluxuntil the solution was colourless (ca. 2 h). Evaporation at100 "C under high vacuum and trituration with ethanolgave the endo-adduct (94 mg), m.p. 159-167" (decomp.)(from chloroform-ethanol) (Found: C, 88.3; H, 6.7.C,,H,,O requires C, 88.6; H, 6.9), vmaX 1 762, 1 772, and1 600 cm-1, 6 7.35-6.9 (10 H, m), 6.29 (2 H, m, olefinic),3.02 (2 H, quint, J ca. 2 Hz, bridgehead methine), 2.53br(1 H, d, J 9 Hz, CH,), 2.0br (2 H, s, methine), 1.25 7 H (6 H,s, 2 x Me and 1 H, d, J 9 Hz, CH,).Reduction of this adduct as in the preceding experimentand crystallisation from chloroform-ethanol gave thealcohol, m.p. 193-195" (Found: C, 88.0; H, 7.4. C,,H,,Orequires C, 88.1; H, 7.4y0), vmx 3 350br cm-l, 6 (CD,),SO7.4-6.9br (10 H, s), 6.3br (2 H, s, vinyl), 5.49 (1 H, d, Jca. 5 Hz, HCO), 2.71br (2 H, s, bridgehead methine), 2.46(1 H, d, J 9 Hz, CH,), 2.17 (2 H, s, methine), 1.18 (1 H, d,J 9 Hz, CH,), and 0.97 (6 H, s, CH,) ; the OH resonance wasobscured by the peak due to water in the solvent.Reduction of Cyclopentadiene-1 ,3-Diphe~ylbenzo c furanA dducts.-Hydrogenation of the endo-cyclopentadiene-1 ,3-diphenylbenzocfuran adduct over platinum at atmo-spheric pressure (20 "C) in the usual way gave the majorcyclopentene-l,3-diphenylbenzocfuran adduct describedby Wittig and Burger,ll m.p. 134-136". Correspondingreduction of the exo-cyclopentadiene-1,3-diphenylbenzoc-furan adduct gave the minor cyclopentene-1 ,3-diphenyl-benzocfuran adduct, m.p. 207-209". The exo-cyclo-pentene adduct was unchanged after being heated in boilingtoluene (18 h) t.l.c. over silica in benzene-petroleum (2 : 3).6/2621 Received, 23rd Decembev, 1975