J . Org. C h e m . 1988, 53,196-198
196
shown in Table 11). The mixture was mixed with 2% Na2C03 (200 mL) and was extracted with ether (100 mL X 4). The extract was washed with 1% Na2CO3(100 mL X 2), dried with MgS04, and concentrated. Kugelrohr distillation of the residual oil gave a mixture of isomers 5 and 6. Their structures were confirmed by 'H NMR, GC-MS, and IR spectra. The ratios obtained from peak areas by GLC were corrected according to response Factors obtained from mixtures of known concentrations of 5 and 6 (see Table 11). N-Methyl-N-(2,2-dimethylpropyl)benzylamine (8). T o a mixture of N-methylbenzylamine (2.45 g, 20 mmol) and 30% NaOH (7 g) was added pivaloyl chloride (2.60 g, 22 mmol) a t 0 "C with vigorous stirring. After the mixture was stirred for 1 h at room temperature, water was added to the mixture. The ethereal extract of the reaction mixture was washed with water, dried, and evaporated to give 3.88 g (94%) of N-benzyl-Nmethylpivalamide: bp 160 "C (12 mmHg, Kugelrohr); 'H NMR (CDC13) 6 1.34 (9, 9 H, CH3), 2.96 (s, 3 H, NCHB), 4.63 (s, 2 H, NCH2C), 7.2 (m, 5 H); IR (Nujol) 1635 cm-'; exact mass calcd for C13HlgNO 205.1466, obsd 205.1476. Then a solution of N-benzyl-N-methylpivalamide (1.527 g, 7.4 "01) in ether (5 mL) was added slowly to a suspension of LiAlH4 (440 mg, 12 mmol) in ether (5 mL). After the mixture was stirred for 1.5 h at room temperature, the reaction was quenched with a saturated aqueous solution of potassium sodium tartrate, and extracted with ether. The ethereal extract was dried (MgS04), concentrated, and distilled to give 1.343 g (95%) of 8: bp 140 "C (120 mmHg, Kugelrohr) [lit. bp 38-41 "C (0.7 mmHgI7]. Registry No. la, 51951-99-6; lb,111267-94-8; IC, 111267-95-9; Id,111267-96-0;le,111267-97-1;2f,54600-29-2;2g, 17877-17-7; 3a,111267-98-2;3b,111267-99-3;3c,111268-00-9;3d,111268-01-0; 3e,111268-02-1;3f,111290-73-4;3g,111268-03-2;5a,91338-96-4; 5b,70160-72-4;5c,70161-02-3;5d,70160-91-7;5e, 6565-69-1;5f, 91562-61-7; 5g, 51180-63-3; 6a,73676-26-3; 6b,70160-93-9; 6d, 70160-97-3;6e,5300-21-0; 6f,6908-75-4;6g,332-14-9; 7,103-83-3; 8,68723-29-5; PhCH2NHMe, 103-67-3;PhCH2NHPr-i, 102-97-6; t-BuNH2,75-64-9; PhCHZNHEt, 14321-27-8;ClCHZTMS, 234480-1; TMSCH,NHBu-t, 79250-80-9; PhCH,Br, 100-39-0; C(Me,)COCl, 3282-30-2; C(Me3)CON(Me)CH2Ph,73551-24-3; N-cyclohexylbenzylamine, 4383-25-9. (7) Gribble, G. W.; Jasinski, J. M.; Pellicone, J. T.; Panetta, J. A. Synthesis 1978, 766. (8) Jones, F. N.; Hauser, C. R. J . Org. Chem. 1962, 27, 1542. (9) Babayan, A. T.; Tagmazyan, K. Ts.; Babayan, G. T. Dokl. Akad. Nauk Arm. SSR 1966,42, 23; Chem. Abstr. 1966,65, 2149g. (10) Wellcome Foundation Ltd. Br. Pat. 881 265, 1961; Chem. Abstr. 1962, 57, 8500a. (11) Fery, L. P. A.; Hove, L. van Bull. Sac. Chim. Belg. 1959,68,65; Chem. Abstr. 1961, 55, 1604f.
Photosensitized C o p e Rearrangement of syn -7-( 1,2-Butadienyl)bicyclo[2.2.l]hept-2-ene [syn -7-(3-Methylallenyl)n0rbornene]~ James A. Duncan,* Luann Y. Aki, Michael J. Absalon, Katy S. Kwong, and Robert T. Hendricks
Department
Chemistry, Lewis and Clark College, Portland, Oregon 97219
of
H
I
H
1
2
3
M
H
I
CH,I
4
5
1
6
vinyl systems.2 For example,2b at 250 "C, syn-7ethenyl-anti-7-methoxynorbornene (4) and its anti,syn epimer 5 were found to give the same formal Cope product, l-methoxy-3a,6,7,7a-tetrahydroindene; 2-methoxybicyclo[3.2.2]nona-2,6-diene, a formal [ 1,3] sigmatropic shift product, was also formed in each case. These results were interpreted in terms of biradical processes initiated by cleavage of the 1,7-bond in 4 or 5. Furthermore, Bersan3 has found that the parent vinyl hydrocarbon syn-7ethenylnorbornene is stable at 250 "C, and at 320 "C it decomposes without rearrangement. Thus, the allenyl group affords an improved pathway for rearrangement relative to a vinyl group in these systems, and we have interpretedlb the 1 2 thermal rearrangement in terms of an orbital symmetry allowed4 [,2, + .2, + (T2s+ T2a)1 augmented eight-electron pericyclic Cope process. We now report on a comparative study of the separate triplet-sensitized photochemistry of bicyclic allenes 1 and 3. In the p a d b we separated small amounts (
