J . Ory. Chem., Vol. 37, No. 14, 1972 2361
NOTES a Beckman IR-5, nmr spectra a Varian A-60, spectrometer unless otherwise noted. A consolidated Electrodynamics 21-102 spectrometer was used for obtaining mass spectra. 4-Acetoxy-3-methyl-l-naphthyl-p,p-dimethyl Acrylate (4).-A stirring solution of 26.05 g (0.12 mol) of menadiol-1-acetate7 and 17.2 g (0.145 mol) of p,p-dimethylacryloyl chloride8 in 200 ml of chloroform was refluxed for 2.5 hr under nitrogen and cooled to 25", followed by addition of 200 ml of water. The customary work-up afforded a viscous oil. Crystallization from hexane gave 35.0 g (97.394) of 4 as white crystals: mp 101-103'; ir (CHC18) v 1755, 1735 cm-l; nmr (CDC18) T 8.02 (d, 3 H, J = 1.2 Hz), 7.77 (d, 3 H , J = 1.0 Hz), 7.72 (s, 3 H ) , 7.61 (s, 3 H), 3.93 (m, 1 H ) , 2.86' (broad s, 1 H ) , and 2.34 (m, 4 H ) . Two recrystallizations from ether increased the melting point to 103-104.5". Anal. Calcd. for C18H1gOa: C, 72.47; H, 6.08. Found: C, 72.59; H , 6.26. 3- (3-Methyl-2-butenoyl)-4-hydroxy-2-methyl1-naphthylAcetate (5).-To a mechanically stirred suspension of aluminum chloride (14.3 g, 0.107 mol, 4 equiv) in 100 ml of methylene chloride was added, over a 10-min period, a solution of 8.0 g (0.0268 mol) of 4 in 50 ml of methylene chloride. The reaction was monitored by ir and continued until, after about 2.0 hr, the 1735cm-' absorption was replaced by the 1635-cm-l absorption of the enol. Only a small amount of the cyclized ketone 6 was detectable by a peak a t 1685 cm-'. The reaction mixture was then poured onto a mixture of 600 g of ice and 100 ml of hycrochloric acid, stirred for 15 min, and separated. The aqueous layer was extracted four times with 100-ml portions of methylene chloride and the combined organic phases were worked up in the usual way. There was obtained 8.28 g of crude 5 as a n orange gum: ir (CHC13) v 1755, 1635 cm-'; nmr (CDC18) T 8.04 (d, 3 H , J = 1.25 Hz), 7.83 (d, 3 H , J = 1.0 Ha), 7.65 (s, 3 H ) , 7.58 (s, 3 H), 4.45 (m, 1 H ) , 2.5 (m, 3 H ) , 1.53 (m, 1 H ) , and -3.08 (s, 1 H). Purification of this intermediate was not attempted in view of its facile cyclization. 6-Acetoxy-3,4-dihydro-2,2,5-trimethyl-2H-naphtho [ 1,241pyran-4-one(6).-A solution of 35.0 g (0.117 mol) of crude 5 in 100 ml of benzene containing 19.7 ml(O.141 mol) of triethylaminewas stirred for 12 hr a t room temperature. Evaporation of the solvent and recrystallization from hexane gave 25.3 g (72.5%, based on 4) of 6. Two further recrystallizations from ether afforded 16.2 g of 6 as yellow crystals: mp 142-143'; ir (CSn, IR-7) v 1765, 1683 cm-I; nmr (CDCl8) T 8.49 (s, 6 H ) , 7.59 (s, 3 H ) , 7.45 (s, 3 H ) , 7.24 (s, 2 H ) , 2.54 (m, 3 H ) and 1.73 (m, 1 H ) ; mass spectrum m/e 298 (RI), 255. Anal. Calcd for Cl6H,,O4: C, 72.47; H , 6.08. Found: C, 72.43; H , 5.87. 3,4-Dihydro-4,6-dihydroxy-2,2,5-trimethyl-2H-naphtho [ 1,241pyran (7).-A solution of 8.0 g (0.0268 mol) of 6 in 400 ml of ether was added gradually to a suspension of 4.8 g (0.126 mol) of lithium aluminum hydride in 200 ml of ether. After a 6-hr period the excess hydride was destroyed by slow addition of 10 ml of 95% ethanol and then by addition of water until bubbling ceased. The ethereal solution was decanted from the solids, the latter were leached with ether, and the combined ether phases were washed and evaporated. The solid residue was stirred with hexane, washed with hexane, and air dried, yielding 5.88 g (90.57,) of 7 as tan crystals, mp 153-155" dec. Two recrystallizations from acetone-carbon tetrachloride gave white crystals of 7 : mp 138-140'; ir (KBr, IR-7) v 3410 cm-l (s); nmr (1OyoDMSO-d6-CDC18) T 8.57 (s, 3 H ) , 8.53 (s, 3 H ) , 7.89 (d, 2 H), 7.54 (6, 3 H), 6.06 (d, 1 H ) , 5.08 (m, 1 H ) , 2.63 (m, 2 H ) , and 1.92 (m, 2 H ) ; mass spectrum m/e 240 (Ill - H20). Anal. Calcd for C16H1803: C, 74.39; H, 7.02. Found: C, 74.61; H , 7.11. 2,2,5-Trirnethyl-ZH-naphtho [ 1,241pyranyl-6 Acetate @).-A solution of 10.05 g (0.039 mol) of diol 7 in 50 ml of acetyl chloride was stirred for 25 min a t room temperature and then concentrated to a dark solid. Benzene (75 ml) was added and the solution was refluxed for 12 hr, cooled, treated with Darco G-60, filtered through Super-Cel, and finally evaporated under reduced pressure. Crystallization from hexane afforded 9.15 g (8070 yield) of 8 as tan crystals, mp 115-118'. Two recrystallizations from ether-hexane gave 8 as white crystals: mp 121.5-122.5'; ir (CHC1,) v 1750 cm-'; nmr (CDC13)T 8.54 (s, 6 H), 7.80 (s, 3 H ) , (7) R. R. Raker, T. H. Davies, L. McElroy, and G. H. Carlson, J . Amer. Chem. Soc., 6 4 , 1096 (1942). (8) W. Bridge, R . G. Heys, and A. Robertson, J . Chem. Soc., 283 (1937).
7.63 (s, 3 H ) , 4.4, 3.48 (q, 2 H , J = 10.0 Hz), 2.34 (m, 3 H ) , and 1.84 (m, 1H ) ; mass spectrum m/e 282 (M). Anal. Calcd for C18H1803: C, 76.57; H, 6.43. Found: C, 76.84; H , 6.55. 3,4-Dihydro-6-methoxy-2,2,5-trimethyl-2H-naphtho [ 1,241pyran-4-01@).-To a cooled ( 5 " ) solution of 1.06 g (4.1 mmol) of 7 in 35 ml of D M F under nitrogen was added 0.21 g (4.6 mmol) of sodium hydride dispersion. The mixture was stirred for 10 min after the gas evolution subsided, followed by addition of 1.98 g (0.014 mol) of methyl iodide. After stirring for 0.5 hr the reaction mixture was poured into 200 ml of water and 100 ml of chloroform and worked up in the usual way. The product crystallized from hexane (0.912 g, 8.5% yield) as tan crystals: mp 127-129'; nmr (10% D>TSO-d6-CDC13) T 8.57 (s, 3 H ) , 8.53 ( 6 , 3 H ) , 7.92 (d, 2 H , J = 4.5 Hz), 7.52 (s, 3 H ) , 6.20 (s, 3 €I), 5.1 (m, 1 H ) , 2.58 (m, 2 H ) , and 1.96 (m, 4 H ) ; mass spectrum m/e 272 (M), 254,239. 6-Methoxy-2,2,5-trimethyl-2H-naphtho [ 1,241pyran (lo).-A solution of 4.55 g (0.0167 mol) of 9 in 40 ml of acetyl chloride was stirred for 0.5 hr a t room temperature. Concentration of the dark solution gave a solid to which was added 150 ml of benzene and the solution was refluxed for 12 hr. After cooling to 25', the solution was diluted with 200 ml of water and worked up as usual. The resultant dark oil was chromatographed on 100 g of silica gel. The hexane eluates were combined and evaporated, affording 4.0 g (94.5%)of 10,a viscous, yellow oil which crystallized upon standing: nmr (CDC13) T 8.55 (s, 6 H ) , 7.63 (s, 3 H ) , 6.2 (s, 3 H), 4.48, 3.43 (9, 2 H, J = 10.0 Hz), 2.58 (m, 2 H ) , and 1.92 (m, 2 H ) ; mass spectrum m/e 254 (M). An analytical sample was prepared by repeated chromatography on basic alumina (hexane). Anal. Calcd for C17Hlb02: C, 80.28; H , 7.13. Found: C, 80.36; H , 7.07. 2,2,5-Trimethyl-2H-naphtho[ 1,2-b]pyran-6-01 (1l).-A sample of 0.258 E 11.0 mmol) of the diol 7 was heated for 15 min a t 160" under nitrogen and evaporated for 1 hr in vacuo a t 50", affording alcohol 11: ir (CHC13) v 3600, 3400 em-'; nmr (10% DMSO-dcCDC1,) T 8.62 (s, 6 H ) , 7.7 (s, 3 H ) , 4.46, 3.49 (9, 2 H , J = 10.0 Hz), 2.75 (m, 2 H ) , 2.52 (broad s, 1 H ) , and 1.99 (m, 2 H ) . Not appreciable amounts of impurities were noted in the nmr spectrum. Further attempts a t purification resulted in oxidative decomposition of the pyranol 1 1. 2-(~,~~-Dimethylallyl)-3-methyl-1,4-naphthoquinone (3).-A solution of 8.0 g (26.8 mmol) of enol 5 dissolved in 100 ml of anhydrous ether was added slowly to 8.0 g (0.211 mol) of lithium aluminum hydride suspended in 150 ml of ether. The mixture was stirred overnight a t room temperature, the excess hydride was deromposed with a minimum amount of water, and the ether supernatant was worked up as described earlier. The 10,20, and 40% benzene-hexane eluates of an alumina chromatography were combined after ir examination, giving 2.32 g (36.1%) of 3: ir (CHCl3) v 1660 cm-l (vs); nmr (CDC13) T 8.31 (d, 3 H , J = 1.25 Hz), 8.22 (d, 3 H , J = 1.0 Hz), 7.83 (s, 3 H ) , 6.35 (broad d, 2 H , J = 7.0 Hz), 4.97 (broad t, 1 H, J = 7.0 Ha), and 2.17 (multiplet, 4 H ) . Y
Registry N0.-3, 957-78-8; 4, 34638-45-4; 5 , 3463846-53 6 , 34638-47-6; 7, 34638-48-7; 8, 16511-15-23 9, 34638-50-1 ; 10, 34638-51-2; 11, 34638-52-3.
A Convenient Synthesis of Benzocyclobutene J. HODGE ?VIARKGRAF, * SALVATORE J. BASTA,^ PETER Ilf. W E G E ~
AND
Department of Chemistry, Williams College, Williamstown, Massachusetts 01167 Received January 31, 1972
In connection with current studies on strained heterocyclic systems, we required a supply of benzocyclobutene (2).2 The preferred pathways to this compound (1) Based on the Honors theses, Williams College, of 9. J. Baata (1972) and P. M.Wege (19713. (2) For a recent review of benLocyclobutene and its derivatives, see I. L. Klundt, Chem. Rev., 70, 471 (1970).
2362
J . Ory. Chem., Vol. $7, No. 14, 1972
NOTES
have previously involved high temperature pyrolyses in vacuo (without or with ultraviolet irradiation) of 1,3dihydroisothianaphthene 2,2-dioxide3v4 or hydrogenation of 1,2-diiodobenzocyclobutene.6 The former method requires special apparatus, while the latter procedure involves lengthy purifications and a specially aged catalyst system. Mindful of these limitations, we directed our attention to benzocyclobutenyl acetate (l),which is readily available from the cycloaddition of bensyne to vinyl acetateU6Although there are no reports in the literature of the reductive cleavage of 1 to 2, the hydrogenolyses of benzylic and allylic esters are known. Two such procedures were studied in the present case. Treatment of 1 with tributyltin hydride failed t o give any benzocyclobutene under the same free radical initiation conditions developed by Khoo and Lee7 for a variety of benzylic esters; vpc analysis indicated that only starting material was recovered. The conversion of 1 t o 2 was smoothly effected, however, by a dissolving metal reduction analogous t o the Henbest reaction. That process, which is a reductive cleavage of allylic acetates by lithium in ethylamine, is the key step in the reduction of a,b-unsaturated ketones
0
r
1
3
4
1
the acetoxy radical. It is interesting that cleavage to the benzylic carbanion occurs as readily as it does, since this species is otherwise difficult to generate. Finnegan has reported that treatment of 2 with butylpotassium or amylsodium resulted in nuclear metalation ortho t o the four-membered ring to give anion 5." It has also
@CQl 5
6
been observed that hydrogen exchange at C-2 of 1,2dihydroeyclobuta [blquinoline (6) could not be effected by sodium ethoxide in ethanol-0-d.12 To our knowledge this reduction has not previously been applied to the cleavage of benzylic esters. Work is currently in progress to define the influence of the ester moiety and the range of benzylic groups.
2. Ac,O
Experimental Section
Rl
to the corresponding 0lefin.*1~I n the present study some attention was directed toward the choice of solvent. Ethylamine was incffectual and ethylenediamine'O afforded five products, none of which was 2; from the vpc analysis is was inferred that o-xylene and o-tolualdehyde were included in the product mixture. Liquid ammonia proved satisfactory as the solvent and moderately good yields of 2 n-cre obtained. By this route benzocyclobutene is available in two steps by standard procedures.
m 0 Ac 1
In this reaction, which proceeds via the anion radical 3, the intermediate anion 4 is produced by the loss of
Li, NH, I - B ~ O H ,THF.
2
(3) (a) 17.1. P. Cava and A. A . Deana, J . Amer. Chem. Soc., 81, 4266 (1959); (b) J. A . Oliver and P. A . Ongley, Chem. I n d . (London), 1024 (1965). (4) Y. Odaira, K. Yamaji, and S. Tsutsumi, Bull. Chem. Soc. J a p . , 37, 1410 (1964). ( 5 ) (a) M. P. Cava and D. R. Kapier, J . Amer. Chem. Soc., 80, 2255 (1958); (b) M. P. Cava and D. R . Kapier, ibid.,79, 1701 (1957). (6) H. H. Wasserman and ,J. Solodar, ibid.. 87, 4002 (1965). (7) L. E. Khoo and H. H. Lee, Z'etraliedron. Lett., 4851 (1968). (8) A . S. Hallswortli, H. B. Henhest, and T. I. Wrigley, J . Chem. Soe., 1969 (1U57). (9) (a) P. &I. McCurry, Jr., Tetrahedron Lett., 1841 (1971); (b) P. M . McCurry, Jr., ibid., 1845 (1971); ( c ) D. Caine and F. N. Tuller, J . Amer. Chem. Soc., 93, 6311 (1971). (10) IT. C. Brown, S. Ikegami, and J. €1. Kawakami, J . O w . Chem., 31, 3243 (1970).
Boiling points are uncorrected. Instrumental data were obtained from a Perkin-Elmer 237-B infrared spectrophotometer; a Cary 14 ultraviolet spectrometer; a Varian T-60 nuclear magnetic resonance spectrometer, with tetramethylsilane as an internal standard; an AEI MS-9 mass spectrometer; and a Varian Aerograph 202B gas chromatograph, with a 12-ft 10yo Dow 710 column. Benzocyclobutene (2 ).-To a magnetically stirred solution of lithium (0.57 g, 0.082 g-atom) in liquid ammonia (46 ml) contained under a nitrogen atmosphere in a flask cooled by n Dry Ice-acetone bath was added dropwise a solution of benzocyclobutenyl acetatee (6 0 g, 0.037 mol) and tert-butyl alcohol (2.75 g, 0.037 mol) in anhydrous tetrahydrofuran (16 ml). The reaction solution was stirred for 2 . 5 hr a t Dry Ice-acetone temperature: warmed to room temperature, quenched by the addition of solid ammonium chloride, diluted with water, alloRTed to remain overnight, and extracted with diethyl ether. The combined extract was washed (dilute HC1, water, and saturated KaC1 solution), dried (MgSO,), concentrated (vpc analysis of the residue indicated the presence of only 2 ) , and distilled to give 1.6 g (42%) of 2: bp 70-71" (50 mm); 12% 1.5404; ir (film) 1462, 779, 715 cm-l; nmr (CCla) 6 3.16 (s, 4); uv max (9570 EtOH) 259.5 nm (e 1230), 265.5 (1855), 271.3 (1830); mass spectrum (70 eV) m/e (re1 intensity) 104 (loo), 103 (47), 78 (3X), 77 (19), 51 (20), 30 (10). The above spect'ral data were identical wit.h those obtained with an anthentic sample of 2 prepared by the hydrogenolysis of 1,2-diiodobenzocyclobuteneP
Registry No.--2,4026-23-7. Acknowledgment.-Acknowledgment is made t o the donors of the Petxoleum Research Fund, administered by the American Chemical Society, for support of this research. In addition, funds from a grant to IVilliams (11) R . 4 . Finnegan, ibid., 30, 1333 (1965). (12) J. H. hlarkgraf, R. J. K a t t , W.L. Scott, and R . S . Shefrin, i b i d . , 34, 4131 (1969).
J. Orq. Chem., Vol. 37, No. 14, 1976 2363
NOTES College from the Alfred P. Sloan Foundation are gratefully acknowledged. The authors also thank Dr. Walter J. McMurray (Yale University School of Medicine) , through whose courtesy the mass spectral data were obtained.
1
2
3
Cyclopentenones. A n Efficient Synthesis of cis-Jasmone 8
4 employing diisobutylaluminum hydride in toluene at
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 16615 Received January 6 , 1976
cisJasmone ( 9 ) is found in the flower oils of several varieties of Jasminum and is indispensable in the reproduction of jasmine fragrance from substances of synthetic origin. Total syntheses of cis-jasmone have been reported;' however, the routes employed are lengthy and suffer from low over-all yields. Jasmone has received considerable attention as a result of new methods of synthesizing 1,4diketones which have been key intermediates leading to the cyclopentenone system. We have developed a synthesis which allows the production of cis-jasmone in -40% over-all yield from the readily available cyclopentadiene. I n addition, cyclopentadiene is easily transformed into A3-cyclopentenones with substitution adjacent to the carbonyl function (e.q., 6). A3-Cyclopentenones of type 6 are poten-
-78". The cis double bond present in jasmone was introduced in 7001, yield by treatment of the hemiacetal 4 with the ylide derived from propyltriphenylphosphonium bromide in dimethyl ~ulfoxide.~The resulting alcohol could be oxidized with Jones reagent a t 0" in acetone to afford a quantitative yield of the A3-2-(cis2-penteny1)cyclopentenone(6). Initial attempts to isomerize the A3-cyclopentenone 6 to the more stable a,p-unsaturated ketone 7 employing aqueous sodium hydroxide-ethanol proved disappointing. The predominant product 'was the desired dienone 7; however, the yields ranged from 50 to 60%. Isomerization of the double bond mas successfully accomplished in 90% yield with 2% aqueous sodium hydroxide at -70". The dienone 7 was transformed into cis-jasmone (9) by addition of methyllithium followed
n
0 9
J0 6
5
4
PAUL A. GRIECO
7
tially versatile intermediates and, moreover, they can be expected to equilibrate to the more stable a,p-unsaturated ketone (e.q., 7). The starting point for the present synthetic scheme was the position-specific addition of dichloroketene to cyclopentadiene.2 Treatment of a solution of cyclopentadiene and dichloroacetyl chloride in hexane a t 0" with an excess of dry triethylamine in hexane resulted in an 85% yield of 7,7-dichlorobicyclo [3.2.0]hept-2-en6-one (1). Dechlorination was effected with excess zinc dust in glacial acetic acid a t -60" for approximately 1 hr to afford the bicyclic ketone 2 in >90% yield. Treatment of a solution of 2 in glacial acetic acid with 30% aqueous hydrogen peroxide a t 0" for 24 hr produced in 90% yield the bicyclic lactone 3.3 The lactone 3 was reduced quantitatively to the hemiacetal (1) (a) L. Crombie and 6. H. Harper, J . Chem. SOC.,869 (1952); (b) S. H. Harper and R. J. D. Smith, ibid., 1512 (1955); (e) J. H. Amin, R. K. Razden, and S. C. Bhattacharyya, Perfum. Essent. Oil Rec., 49, 502 (1958); (d) G. Stork and R . Borch, J . Amer. Chem. SOC.,86, 936 (1964); (e) K. S. Sido, Y . Kawasima, and T . Isida, Perfum. Essent. 0 2 2 Rec., 67, 364 (1966); (f) G. Btichi and R . Wuest, J . O w . Chem., 31, 977 (1966); (g) L. Crombie, P. Hemesley, and G. Pattenden, J. Chem. Sac. C, 1024 (1969); (h) J. E. MoMurry and T. E. Glass, Tetrahedron Lett., 2575 (1971); (i) G. Stork, F. Rouessac, and 0. Gringore, J . Amer. Chem. Sac., 93, 3091 (1971); ( j ) G. Bttchi and B. Egger, J . Org. Chem.. 36, 2021 (1971); (k) J. E. McMurry and J. Melton, J . Amer. Chem. Sac., 93, 5309 (1971). (2) H. C. Stevens, D. A. Reioh, D. R . Brandt, K. R. Fountain, a n d E . J. Gaughan, ibid., 87, 5257 (1965); L. Ghosea, R. Montaigne, and P. Mollet, Tetrahedron Lett., 135 (1966). (3) E. J. Corey, 2. Arnold, and J. Hutton, ibid., 307 (1970).
by oxidation of the resulting carbinol 8 with chromium trioxide.lj cis-Jasmone (9), Y~~~~~ 1685 and 1640 ern-', was characterized by its 2,4-dinitrophenylhyd r a ~ o n e . ~Ir and nmr spectra of synthetic cis-jasmone were identical with those of an authentic sample.6 The present synthesis allows the conversion of cyclopentadiene to cis-jasmone (9) in seven steps with an over-all yield of -40%. Experimental Section Microanalyses were performed by the Spang Microanalytical Laboratories, Ann Arbor, Mich. Melting and boiling points are uncorrected. The following spectrometers were used: nuclear magnetic resonance (nmr), Varian T-60 and A-60D (in S units, with TMS as internal reference in CCl, unless stated otherwise); infrared (ir), Perkin-Elmer Model 247 and Beckman IR-8; mass spectrometer (mass spectrum) LKB-9. Vapor phase chromatography (vpc) analyses were performed on a Varian Aerograph Model 90-P instrument using silicone rubber SE-30 and Carbowax 20 M columns. Pre-coated PLC silica gel F-254 Merck plates were used for preparative tlc. 7,7-Dichlorobicyclo[3.2.0] hept-2-en-6-one (l).-To a vigorously stirred solution of 27.2 g of freshly distilled cyclopentadiene, 30.5 g of dichloroacetyl chloride, and 200 ml of hexane (dried over molecular sieves) was added 21.7 g of dry triethylamine in 200 ml of hexane over a period of 1.5 hr. After stirring for 15 hr under an atmosphere of nitrogen, the reaction mixture was filtered and (4) R. Greenwald, M. Chaykovsky, and E. J. Corey, J . Org. Chem., 28, 1128 (1963); E. Hamanaka, Ph.D. Thesis, Harvard University, Cambridge, 1967. The cis geometry for the double bond in 5 is identicated by the absence of the absorption characteristic of trans CH=CH- a t 10.3-10.4 P . The subsequent synthetic transformations also allow the cis assignment. ( 5 ) Y . R. Naves and .4.V. Grampoloff, Helu. Chim. Acta, 26, 1500 (1942). (6) Kindly supplied by International Flavors and Fragranoes, Union Beach, N. J.
