1354 zyxwvutsrqponm J. Org. Chem. 1992,57,1354-1362 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Found H, 7.07; C, 75.55; N, 5.18. Acetamide of 2e: mp l e 1 4 1 OC (from methanol);'H NMR 6 1.97 (3 H, a), 3.03 (1 H, dd, J zyxwvu = 13.6 and 7.1 Hz), 3.09 (1 H, dd, J = 13.6 and 6.4 Hz), 3.70 (3 H, s), 3.83 (3 H, s), 5.24 (1 H, q, J = 7.1 zyxwvutsr Hz), 5.89 (1 H, br d), 6.42 (1 H, s), 6.59 (1 H, d, J = 8.1 Hz), 6.75 (1 H, d, J = 8.1 Hz), 7.17-7.30 (3 H, m); 13C NMR 6 23.38, zyxwvu 42.11,54.52,55.72,55.86, 111.07,112.62,121.42,126.75,127.42, 128.58,129.58,141.39,147.81,148.71,169.34; MS mle 299 (M'), 241 (M - NHAc). Anal. Calcd for C18HzlN03: H, 7.07; C, 72.21; N, 4.68. Found: H, 7.02; C, 71.98; N, 4.63. Acetamide of 2f: 'H NMR 6 1.96 (3 H, s), 3.02 (2 H, d, J = 7.08 Hz), 5.20 (1 H, q, J = 7.6 Hz), 5.88 (1 H, br d), 5.90 (2 H, s), 6.00 (d, J = 7.7 Hz), 6.53 (1 H, s), 6.67 (1 H, d, J = 7.7 Hz), 7.16-7.37 (5 H, m); 13C NMR 6 23.42,42.21,54.64, 100.85, 108.07, 109.61,122.31,126.64,127.46,128.60,130.99,141.35,146.21,147.54, 169.29;MS mle 282 (M - l), 223. Acetamide of 2g 'w NMR 6 23.04,42.82,54.47,55.12,98.73, 107.33, 126.73, 127.19, 128.41, 140.00, 142.00, 160.60, 169.71. Acetamide of 3g 'w NMR 6 22.98,42.60,54.81,55.18,99.02, 104.97, 126.41, 128.23, 129.24, 137.78, 144.54, 160.82, 169.71. Acetamide of ti. 13C NMR 6 21.03,23.37,42.06,54.38,126.63, 127.34, 128.52, 129.04, 129.16, 134.05, 136.07, 141.58, 169.35. Acetamide of 3i: 'w NMR 6 21.07,23.37,42.41,54.18,126.50, 126.57, 128.30, 129.24, 129.31, 137.06, 137.42, 138.40, 169.29. Acetamide of 2j: '% NMR 6 23.38,41.76,54.53,126.69,127.65, 128.68, 130.63, 132.38, 135.80, 140.90, 169.38. Acetamide of 3j '% NMR 6 23.31,42.38,53.85,126.78,128.01, 128.43, 128.48, 129.24, 133.09, 136.79, 140.09, 169.38. Acetamide of 2 k mp 154-155 "C; 'H NMR 6 1.93 (3 H, e), 2.99 (1 H, dd, J = 13.7 and 7.3 Hz), 3.06 (1 H, dd, J = 13.7 and 6.9 Hz), 3.77 (3 H, s), 3.79 (3 H, s), 5.17 (1 H, q, J = 7.3 Hz), 5.9H.02 (1 H, br d, J = 7.8 Hz), 6.75-6.85 (4 H, m), 6.96 (2 H, d, J = 8.6 Hz), 7.13 (2 H, d, J = 6.4 Hz); 13C NMR 6 23.32,41.59, 54.14, 55.17,55.25,113.71, 113.90, 127.85, 129.48,130.29,133.70, 158.22, 158.79, 169.25; MS mle 296, 241. Acetamide of 21: 'H NMR 6 1.92 (3 H, s), 2.99 (2 H, d, J = 7.0 Hz), 3.73 (6 H, s), 3.76 (3 H, s), 5.15 (1 H, t, J = 7.0 Hz), 5.87 (1 H, br d), 6.26 (1 H, s), 6.34 (2 H, e), 6.76 (2 H, d, J = 8.6 Hz), 6.79 (2 H, d, J = 8.6 Hz); 13C NMR 6 23.35,41.54,54.62,55.32, 98.99, 104.89,113.76,130.27,160.04,129.24,144.12,169.36; MS mle 329 (M+), 270 (M - NH2Ac). trans-la, 103-30-0; trans-lb, 52805-92-2; trans-lc, 14064-41-6;trans-ld, 1694-19-5; trans-le, 3892-92-0; trans-lf, 51003-16-8; trans-lg, 21956-56-9; trans-lh, 74809-43-1; trans-li, 1860-17-9; trans-lj, 1657-50-7; trans-lk, 15638.149; trans-11, 22255-22-7; 2a acetamide derivative, 2155-90-0; 2b acetamide derivative, 138435-22-0; 2c acetamide derivative, 13843523-1; 2d acetamide derivative, 93172-54-4; 28 acetamide derivative, 76306-60-0; 2f acetamide derivative, 76306-61-1; 2g acetamide derivative, 138435-24-2; 2i acetamide derivative, 138435-253; 2j acetamide derivative, 138435-266; 2k acetamide derivative, 93172-56-6; 21 acetamide derivative, 138435-27-5;3b acetamide derivative, 138435-28-6; 3c acetamide derivative, 138435-29-7;3g acetamidederivative, 13843530-0; 31 acetamide derivative, 138435-31-1; 3j acetamide derivative, 138458-90-9. Supplementary Material Available: 'H NMR spectra for the acetamides of 2a-g,i-1 and 3b,c,e,g,i,j (24 pages). This material is contained in many libraries on microfiche, immediately follows this article in the microfii version of the journal, and zy can be ordered from the ACS zyxw see any current masthead page for ordering information. Registry No. Force Field Modeling of Transition Structures of Intramolecular Ene Reactions and ab Initio Transition Structures for an Activated Enophile Bert E. Thomas IV, R. J. Loncharich, and K. N. Houk* Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024-1669 Received May 20,1991 (Revised Manuscript Received November 19,1991) A modification of Allinger's MM2 force field has been developed to rationalize and predict the stereochemistries of intramolecular ene reactions. "hh force field reproduces the stereochemical trends ohserved for intramolecular ene reactions with unactivated enophiles, but gives poor results with activated enophiles. Ab initio molecular orbital calculations on the ene reaction of acrylonitrilewith propene were performed to investigate the change in the transition structure caused by activating substituents. Introduction The intramolecular ene reaction'i2 has been used fre- quently in organic synthesis for the formation of five- and six-membered rings, with control of the stereochemistry in the products. With activating substituents and catalysis A ~~~~ ~~ (1) (a) Hoffmann, H. M. R. Angew-Chem., zyxwvutsrqpo Int. Ed. Engl. 1969,8,556. (b) Oppolzer, W.; Snieckus, V. Angew. Chem., zyxwvutsrqp Int. Ed. Engl. 1978,17,476. (2) (a) Taber, D. F. Intramolecular Diels-Alder and Ene Reactions; Springer-Verlag: New York, 1984. (b) Carruthers, W. Cycloaddition Reactiom in Organic Synthesis; Pergamon Press: Oxford, 1990; Chapter 5. by Lewis acids, reaction temperatures are usually lower and there is greater control of stereochemistry than in simple hydrocarbon cases.3~~ The stereochemistry about the forming CC bond is usually cis for fivemembered rings and trans for six-membered rings. The relationship be- tween the stereochemistries of substituents on the tether and the stereochemistry of CC bond formation is not as easily predicted. In this paper, we present a simple modification of AUinger's MM2 force field6 which modela the transition structures of intramolecular ene reactions (3) Snider, B. B. Acc. Chem. Res. 1980, 13,426. (4) (a) Tietze, L. F.; Beifd, Y. Synthesis 1988,359. (b) Maruoka, K.; Hoshino, Y.; Shirasaka, T.; Yamamoh, H. Tetrahedron Lett. 1988,2Q, 3967. (c) Salomon, M. F.; Pardo, S. N.; Salomon, R. G. J. Org. Chem. 1984,49, 2446. (5) (a) Burkert, U.; Allinger, N. L. Molecular Mechanics; Americaa Chemical Society: Washington DC, 1982. (b) Allinger, N. L. J. Am. Chem. Soc. 1977, 79, 8127. (c) Allinger, N. L.; Yuh, Y. H. Molecular Mechanics 11, QCPE No. 395, Indiana University, Bloomington, IN. 0 1992 American Chemical Society