J. Org. Chem., Vol. 37, NO.19, 1972
DIMETHYLFULVENE-VINYLENE CARBONATE REACTION
3015
Diels-Alder Reaction between Dimethylfulvene and Vinylene Carbonate. Configurational Assignments of and Magnetic Anisotropic Studies in Adducts and Related Compounds’ M. Z. H A Q ~ Department of Chemistry, University of Ottawa, Ottawa K I N 6N6, Canada Received December 13, 1971 Nine new 7-isopropylidenebicyclo[2.2.1]hept-5-ene 2,3-disubstituted derivatives were synthesized. Successful approaches include the reaction of dimethylfulvene with vinylene carbonate to afford exo and endo diastereoisomers of 7-isopropyIidenebicyclo[2.2.1] hept-5-ene-2,3-diol carbonate, la and Ib, in the ratio of 3 : 2, respectively. Hydrolysis of la and lb gave the corresponding diols, 2a and 2b. Treatment of the latter two with thiocarbonyldiiniidazole resulted in the formation of the thionocarbonate, 3a and 3b. Catalytic hydrogenation double bond showed a shielding effect of la, 2a, 2b, and 3a reduced the A5g6double bond. As expected, the on the isopropylidene methyl protons, a deshielding on the H-2,3 exo pair, and a shielding influence on the corresponding endo pair. Desulfurization-decarboxylation of 3 with trimethyl phosphite or Rsney nickel to produce 7-isopropylidenebicyclo[2.2.1] hepta-2,5-diene (4) was unsuccessful. Anisotropic effects of the double bonds on cyclopropyl protons in 7,7-dimethylenebicyclo[2.2.1] hept-5-ene and -hepta-2,5-diene are discussed.
Various aspects of the nuclear magnetic resonance spectra of bicyclo [2.2.l]heptanering systems have been studied in recent years. Initial investigations3 furnished relations between spin-spin coupling constants of ring protons and the stereochemistry. Fraser4 established a method of configurational assignment in 5- and 6-substituted norbornenes. Effects of magnetic anisot’ropy5of the double bond on the bridge methylene protons in norbornene and nonbornadiene, however, have been inconsistent and anomalous. Tori and coworkers6 in 1964 incorrectly ascribed the multiplets centered at r 8.92 and 8.67 to the H-7 syn and H-7 anti, respectively. This assignment was based on the anticipated larger diamagnetic shielding of the double bond for H-7 syn compared to H-7 anti. This assignment was later r e v e r ~ e d ,since ~ long-range coupling was observed between the multiplet at 8.67 and H-5,6 endo pair; stereospecific coupling between t’helatter and H-7 syn in accord with the “W-letter” rule3es* was responsible for this reassignment. More recently, other workersg have clearly (1) (a) This work constituted, in part, *he Ph.D. dissertation of M. 2. Haq, University of Ottawa, Ottawa, Canada, 1967, and was done under the supervision of Professor Robert R. Fraser. The author wishes to thank Professor Fraser for his stimulating guidance during the course of this work, for kindly suggesting t h a t he submit the paper as sole author, and for providing invaluable comments and suggestions on the manuscript. Financial help of the National Research Council of Canada in support of this work is also gratefully acknowledged. (b) M . Z. Haq, $bstracts, 163rd National Meeting of the American Chemical Society, Boston, Masa., dpril 1972, ORCN-100. (2) Meloy Laboratories, Inc., 6715 Electronic Drive, Springfield, Va. 22151. (3) (a) W. D. Kumler, W. J. Schoolery, and F. B. Bruchter, Jr., J . Amer. Chem. Soc., 80, 2533 (1958); (b) E. J. Corey, M. Ohno, S. W. Chow, and R . A. Schemer, ibid., 81, 6305 (1959); ( 0 ) F. A. L. Anet, C a n . J . Chem., 89, 789 (1961); (d) M. M. Anderson and P . M. Henry, Chem. I n d . (London) 2053 (1961); (e) J. Meinwald and A. Lewis, J . Amer. Chem. Soc., 88, 2769 (1961); (f) K. B. Wiberg, B. R. Lowny, and B. Nist, i b i d . , 84, 1954 (1962); (9) K. L. Williamson, ibid., 86, 516 (1963); (h) J. I . Musher, Mol. Phys., 6, 93 (1963); (i) J. Meinwald, Y. C. Meinwald, and T. N. Baker, 111, J . Amer. Chem. Soc., 86, 2613 (1963); (j) J. C. Davis, Jr., and T. V. Van Auken, ibid., 87, 3900 (1965); (k) F. A. L. Anet, H. H. Lee, and J. L. Sudmeier, {bid., 89, 4431 (1967). (4) R. R . Fraser, Can. J . Chem., 40, 78 (1962). ( 5 ) Magnetic anisotropic effects can be calculated employing Nakagawa and coworkerso equation provided that the molecular geometry is known. (6) K. Tori, Y. Hata, R . Muneyuki, Y. Takano, T . Tsuji, and H. Tanida, Can. J . Chem., 42, 926 (1964). (7) K. Tori, A. K . Aono, Y. Hata, R. Muneyuki, T. Tsuji, and H. Tanida, Tetrahedron Lett., No. 1, 9 (1966). (8) For a review, see S. Sternhell, Rev. Pure A p p l . Chem., 14, 15 (1964). (9) (a) B. Franzus, W. C. Baird, Jr., N. F. Chamberlain, T. Hines, and E. I. Snyder, J . Amer. Chem. Soc., 90, 3721 (1968); (b) A. P. Marchand and J. E. Rose, ibid., 90, 3724 (1968).
demonstrated that H-7 syn in nonbornene absorbs1° at lower field than H-7 anti, thus confirming Tori’s later results.7 Furthermore, in norbornadiene,6 the bridge methylene protons experience an unusual deshielding and appear a t r 8.02, whereas in norbornane these protons absorb at 8.80. If the additivity principle of shielding effects could be applied, the signal of bridge methylene protons should appear at r 8.80. This unexpected shielding and deshielding influence of the bridge protons prompted us to undertake the present study. We originally wished to synthesize 7-isopropylidene derivatives of norbornane, norbornene, and norbornadiene to study the anisotropic effects of the double bonds on the isopropylidene methyl protons and see if unusual deshielding similar to that observed in norbornadiene is encountered. This aim, however, could not be accomplished, since we were not successful in synthesizing these compounds. This paper reports (i) syntheses and configurational assignments of 7-isopropylidenebicyclo [2.2.1lhept-5ene-2,3-diol carbonates and their derivatives, and (ii) anisotropic effects of the A5t6 double bond on the isopropylidene methyl protons and H-2,3 exo-endo pairs. I n addition, effects of the double bonds on the chemical shifts of the cyclopropyl protons in 7,7-dimethylenebicyclo L2.2.1]hept-5-ene15 and -hepta-2,5-diene have been examined and the results compared with those of Toris,’ on norbornanes.
Results and Discussion The reaction of dimethylfulvene with vinylene carbonate afforded a mixture of exo and endo isomers of (10) The reverse should be expected according to the suggestions of Jackman,l1 Pople,** and ApSimon and coworkers.18 For a detailed account of mbgnetic anisotropy of the double bond and theoretical consideration, see ref 11-14. (11) L. M. Jackman and S. Sternhell, “Applications of Nilclear Magnetic Resonance Spectroscopy in Organic Chemistry,” Pergamon Press, New York, N. Y., 1969, p 83. (12) (a) J. A. Pople, J . Chem. Phys., 81, 53 (1962); (b) ibzd., 81, 60 (1962).
(13) (a) J. W. ApSimon, W. G. Craig, P. V. Demarco, D. W. Mathieson, L. Saunders, and W. B. Whalley, Chem. Commun., No. i2, 359 (1966); (b) J. W. ApSimon, W. G. Craig, P. V. Demarco, D. W. Mathieson, and W. B. Whalley, Tetrahedron, 28, 2375 (1967). (14) H. Conroy in ”Advances in Organic Chemistry: Methods and Results,” R . A. Raphael, C. E. Taylor, and H. Wynberg, Ed., Interscience, New York, N. Y., 1960, p 265. (15) Synthetic procedures known.16 (16) K. Alder, H. J. Ache, and F. H. Flock, Chem. Ber., 98, 1888 (1960).
3016 J . Org. Chem., Vol. 37, N o . 10, 1978
HAQ TABLE I
NMRSPECTRAL DATAI N Compd
T
UNITSa OF 7-ISOPROPYLIDENEBICYCLO[2.2.1]HEPTANE DERIVATIVES OH
H-5, H-6
H-2, H-3
H-1, H-4
H methyls
la
a
3.81 5.60 6.50 (6, SP 2 Hz) (8) (t, SP 2 Hz) lb 3.70 5.22 6.32 ( t JsP Hz) ( t J sp (qi, SP 2 He) 2a 3.82 7.12 6.34 6.84 (t, SP 2 Hz) (br 8 ) (9 ) (t, SP 2 HE) 2b 3.62 7.46 5.92 6.50 ( t J sp Hz) (br 8 ) ( t J sp Hz) (qiJ sP Hz) 3a 3.78 5.18 6.37 ( t J sp Hz) (8) ( t JsP 3b 3.64 4.82 6.21 ( t Jsp IEz) ( t Jsp (qi,sp 2 H z ) Peak multiplets are represented by br, broad band; m, multiplet; qi, quintet; s, singlet; sp, spacing; t, triplet
w
the adduct 1 in the ratio of 3:2, respectively (Scheme
I). This conclusion was based on the nmr spectrum of the product, which showed two sets of bands (four peaks each) in the intensity ratio of 3:2. Fractional crystallization of the mixed adduct 1 gave pure carbonates la and lb. Hydrolysis of la and l b gaverise to 2a and 2b, which on treatment with thiocarbonyldiimidazole resulted in the formation of 3a and 3b, respectively. Compounds 5a, 6a, 6b, and 7a (see Table 11) were prepared by the catalytic reduction of la, 2a, 2b, and 3a, respectively. Attempts to produce 4 through the reaction of 3 with trimethyl phosphite17 or Raney nickel were unsuccessful. Attempted oxidative decarboxylation1s of 7isopropylidenebicyclo [2.2.l]hept 5 -ene-exo-2,3-dicarboxylic acidle using lead tetraacetate also failed. Configurational Assignments of 74sopropylidenebicyclo [2.2. l]heptd-ene-Z,3-diol Carbonate (1) and Its Derivatives. -Elemental analysis and mass, infrared, and nmr spectral data confirmed the gross structure of 1 (see Experimental Section for details). In la a singlet at r 5.60 (2 protons) was ascribed to the H-2,3 endo pair, since no coupling wit’h the bridgehead protons is ~ b s e r v e d . ~In lb,20 there appeared a triplet at r 5.22 (2 protons) reasonably a ~ c r i b e d ~ ~to- ~the + * H-2,3 ~~~~ exo pair now spin coupled to the bridgehead protons; the latter now appeared as a quintet. The configurations of 2a, 2b, 3a, and 3b follow from their precursors and were confirmed by the multiplicities of the H-2,3 pair (see Experimental Section and Table I). Reduction Products of 7-Isopropylidenebicyclo[2.2.1]hept-S-ene-2,3-diol Carbonate (1) and Its Derivatives. -The structures of the hydrogenation products 5a, 6a, 6b, and 7a follow from their respect’ive unsaturated counterparts and were confirmed by their elemental analyses and infrared and nmr spectral data (see EX-
dimethylfulvene
8.33 (9 )
8.42 8.34 (9)
8.46 is)
8.35 (S )
8.41 (SI
SCHEME Ia
+
= ):[o
-
vinylene c’arbonate
1
2
-
(17) Olefinic bonds can be obtained smoothly from 12-diols. See E. J. Corey a n d R . A. E. Winter, J . Amer. Chem. Soc., 85, 2677 (1963). (18) Numerous examples of oxidative decarboxylation of dicarboxylic acids t o produce double bonds including examples in bicyclic systems are known, e . g . , (a) C. A. Grob and A . Weiss, Helv. Chim. Acta, 48, 1390-(1960); (b) E. E. van Tamelen and S. P. Pappas, J . Amer. Chem. Soc., 85, 3297 (1963); (0) E. J. Corey and J. Casanova, Jr., Ibid., 86, 165 (1963); (d) R . Criegee, C. 0. Edens, J r . , and B. Graham in “Newer Methods of Preparative Organic Chemistry,” Interscience, New York, N. Y . , 1948, p 1. (19) (a) D. Craig, J. J. Shipman, J. Kiehl, F. Widmer, R . Fowler, and A. Hawthorne, J . Amer. Chem. Soo., 78, 4573 (1954); (b) I
