Ethyl 2-(diphenylmethyleneamino)acetate → Ethyl 2-(diphenylmethyleneamino)-2-(pent-4-enyl)hept-6-enoate

Participants

Reaction Conditions

Reaction Steps

A procedure previously described for dialkylation of N-(diphenylmethylene)glycine ethyl ester was used after modifications (see Denmark, S. E.; Stavenger, R. A.; Faucher, A.-M.; Edwards, J. P. J. Org. Chem. 1997, 62, 3375-3389): To a stirred solution of N-(diphenylmethylene)glycine ethyl ester 10 (13.63 g, 51 mmol) in THF (250 mL) was added a solution of KHMDS (11.2 g, 56.1 mmol, 1.1 equiv.) in THF (56 mL) via a cannula at −78° C. over 15 min. After stirring at −78° C. for 1 h, the resulting orange-colored solution was treated with 5-iodo-1-pentene (12 g, 61.2 mmol, 1.2 equiv.). The reaction mixture was allowed to warm to room temperature and stirred for 2 h. The resulting suspension was cooled to −40° C. and another solution of KHMDS (15.3 g, 76.5 mmol, 1.5 equiv.) in THF (77 mL) was added via a cannula over 15 min and stirred for 1 h. 5-iodo-1-pentene (16 g, 81.6 mmol, 1.6 equiv.) was then quickly added to the burgundy-colored mixture, and the reaction was left to warm to room temperature overnight (16 h). The reaction was quenched by addition of saturated NH4Cl solution in water (100 mL). The organics were extracted with ethyl acetate (2×150 mL), washed with Na2S2O3 solution and then with brine. The organic layer was dried over MgSO4, filtered, and concentrated under reduced pressure. The resulting residue was dried in vacuo overnight and used for the next reaction without further purification: 1H-NMR (400 MHz, CDCl3) δ 7.83-7.12 (m, 10H), 5.80 (m, 2H), 5.02 (dd, J=17.2, 1.6 Hz, 2H), 4.96 (dd, J=10.4, 1.6 Hz, 2H), 3.74 (q, J=6.8 Hz, 2H), 2.05 (dd, J=14.0, 7.2 Hz, 4H), 1.92 (m, 4H), 1.45 (m, 4H), 1.13 (t, J=6.8 Hz, 3H); 13C-NMR (100 MHz, CDCl3) δ 174.8, 166.0, 141.3, 138.9, 128.5, 128.2, 127.9, 115.0, 69.2, 60.5, 37.5, 34.4, 23.3, 14.2; HRMS (ESI) m/z for C27H34NO2 [M+H]+ calcd 404.2589. found 404.2577.

Provenance & Evidence