Study on the base-catalyzed reverse vinylogous aldol reaction of (4abeta,5beta)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one under Robinson annulation conditions.
[reaction: see text] We have proposed a pathway for the base-catalyzed reverse vinylogous aldol reaction of (-)-(4abeta,5beta)-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 I, 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.
Payette
Joshua N
JN
Department of Chemistry, Dartmouth College, 6128 Burke Laboratory, Hanover, New Hampshire 03755, USA.
Honda
Tadashi
T
Yoshizawa
Hidenori
H
Favaloro
Frank G
FG
Gribble
Gordon W
GW
D002384:Catalysis; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry*
C511884:(4abeta,5beta)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one; D009281:Naphthalenes; D009930:Organic Chemicals; D014753:Vinyl Compounds