M. Tori, Kenji Hisazumi, Tomonari Wada
Mar 12, 1999
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0
Influential Citations
14
Citations
Journal
Tetrahedron-asymmetry
Abstract
Abstract The imine of ( rac )-2,3-dimethylcyclohexanone 10a with ( S )-(−)-phenylethylamine was reacted with methyl acrylate to yield methyl (1′ S ,6′ R )-3-(1′,6′-dimethyl-2′-oxocyclohexyl)propanoate 4a in 26% (97% ee) after hydrolysis. When (2 RS ,3 R )-2,3-dimethylcyclohexanone 10b was used, the same product 4b was obtained in 59% yield (>99.5% ee) after hydrolysis. When (2 RS ,3 R )-2,3-dimethylcyclohexanone 10b and ( R )-(+)-phenylethylamine were used, the reaction underwent in only 5% yield, the products being 4c , 12 , 13 , 14 , and 15 . Thus, the reaction of 3b with methyl acrylate is a matched case, while that of 3c is a mismatched case. These phenomena are explained by the nonbonded interaction of methyl acrylate with chiral phenylethylamine and the methyl group at the 6′-position of the cyclohexanone ring in the transition state. The propanoate product 4b was successfully transformed into liverwort sesquiterpene (+)-trifarienol A 1 and (−)-trifarienol B 2 in 10 steps. We have developed an HPLC method to determine the ees of 2,2-disubstituted and 2,2,3-trisubstituted cyclohexanones using the corresponding pentafluorophenyl esters.