Study on the Base-Catalyzed Reverse Vinylogous Aldol Reaction of (4aβ,5β)-4,4a,5,6,7,8-Hexahydro- 5-hydroxy-1,4a-dimethylnaphthalen-2(3<i>H</i>)-one under Robinson Annulation Conditions
作者:Joshua N. Payette、Tadashi Honda、Hidenori Yoshizawa、Frank G. Favaloro、Gordon W. Gribble
DOI:10.1021/jo0520036
日期:2006.1.1
We have proposed a pathway for the base-catalyzed reverse vinylogous aldol reaction of (-)-(4a beta,5 beta)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one [(-)-8] under Robinson annulation conditions. For confirmation, 4-(2,6-dimethyl-3-oxocyclohex-1-enyl)butanal (11) and 4-(2,6-dimethyl-5-oxocyclohex-1-enyl)butanal (12), both of which potentially produce enolate 1, were synthesized regioselectively. Unexpectedly, 11 gave a complex mixture, including only a trace amount of (+/-)-8 (less than 5% yield), under these basic conditions. To the contrary, 12 cleanly afforded (+/-)-8 in 66% yield. This result provides evidence for our proposed mechanism of the above reaction.