反应详情

温度

-30 °C

A solution of n-butyl lithium (1.06M. in hexane, 1.13 ml) was added to a solution of diisopropylamine (0.17 ml) in dry THF (8 ml) at -30° C. under dry argon. After stirring at -30° C. for 10 minutes the mixture was cooled to -76° C. and treated with a solution of 1-t-butyldimethylsilyl-4-tritylthioazetidin-2-one (1) (459 mg) in dr THF (4 ml). After a further 15 minutes at -76° C. the stirred mixture was treated with a solution of 4-formyl-1-methylpyrazole (132 mg) (I. L. Finar and G. H. Lord, J. Chem. Soc. 1957, 3314) in dry THF (1 ml). After 20 minutes at -76° C. the stirred mixture was treated with saturated ammonium chloride solution (5 ml) and worked up as for Preparation 1(a) to give two fractions. The less polar fraction contained a trans-isomer (Isomer A) of the title azetidinone (12) (165 mg), an amorphous solid, νmax (CHCl3) 3600-3100, 1735 cm-1 ; δppm (CDCl3) 0.92 (9H, s), 1.1-1.8 (1H, br. signal, exch. D2O), 3.32 (1H, dd, J2 and 2 Hz), 3.50 (1H, d, J2 Hz), 3.76 (3H, s), 4.46 (1H, d, J2 Hz), 7.10-7.60 (17H, m), the Me2Si signals were obscured by the TMS signal. [Found (diethylamine chemical ionisation): MH+, 570 and M+Et2NH]+, 643]. The more polar fraction contained the other trans-isomer (Isomer B) of the title azetidinone (12) (185 mg), an amorphous solid, νmax (CHCl3) 3600-3100, 1735 cm-1 ; δppm (CDCl3) 0.80 (9H, s), 1.7-2.5 (1H, br. signal, exch. D2O), 3.59 (1H, dd, J6 and 2 Hz), 3.70 (3H, s), 3.87 (2H, 2d, J2 Hz and J6 Hz), 6.91 (1H, s), 7.10-7.50 (16H, m), the Me2Si signals were obscured by the TMS signal. [Found (diethylamine chemical ionisation): MH+, 570].

1. temperaturewas cooled to -76° C.
2. customto give two fractions