The Retro-Michael Reaction of 1,5-Dicarbonyl Compounds: Scope and Limitation

摘要

Under catalysis of NaOH or KOH adsorbed on glass wool and by using steam distillation, (20R,S)-4,4,5,14-tetramethyl-18,19-dinor-13,17-seco-5#beta#, 8#alpha#, 9#alpha#, 10#alpha#, 14#beta#-cholestane-13,17-dione (1) and 3,14-dioxo-14,15-seco-5#alpha#-cholestan-15-al (4) gave good yield (>59%) of the corresponding tricyclic compounds (8a,8b and 10a) via a retro-Michael reaction at 250 deg C. While 5-oxo-4-nor-3,5-secocholestan-3-oic acid (6) and ethyl 5-oxo-4-nor-3,5-secocholestan-3-oate (7) afforded low yield (<15%) of the retro-Michael cleavage products (12a, 12b) at the same conditions. Thus, the retro-Michael reaction worked well for 1,5-diketones and 1,5-keto aldehydes but gave poor yield for 1,5-keto esters and 1,5-keto acids.