CONJUGATE ADDITION OF GRIGNARD-REAGENTS TO N-(ALPHA,BETA-UNSATURATED)ACYLPYRAZOLES - DIASTEREOSELECTIVE BETA-ALKYLATION USING 3-PHENYL-L-MENTHOPYRAZOLE
C. Kashima et al., CONJUGATE ADDITION OF GRIGNARD-REAGENTS TO N-(ALPHA,BETA-UNSATURATED)ACYLPYRAZOLES - DIASTEREOSELECTIVE BETA-ALKYLATION USING 3-PHENYL-L-MENTHOPYRAZOLE, Journal of heterocyclic chemistry, 35(3), 1998, pp. 503-511
The conjugate additions of N-(alpha,beta-unsaturated)acylpyrazoles wer
e carried out by the treatment with Grignard reagents in the presence
of cuprous halides. The reaction of a,beta-unsaturated)acyl-3-phenyl-l
-menthopyrazoles 3a-h occurred in higher chemical yields and with asym
metric inductions on beta-position, where the addition of magnesium br
omide as a Lewis acid influenced to the yields and the diastereoselect
ivities. In the case of alpha-methylated a,beta-unsaturated)acyl-3-phe
nyl-l-menthopyrazoles 3i-n, the excellent asymmetric induction on the
alpha-position was also observed through the diastereofacial protonati
on.