Conjugate addition of grignard reagents to N-(α,β-unsaturated)acylpyrazoles. Diastereoselective β-alkylation using 3-phenyl-l-menthopyrazole

✍ Scribed by Choji Kashima; Katsumi Takahashi; Kiyoshi Fukusaka; Akira Hosomi

• Book ID: 102892850
• Publisher: Journal of Heterocyclic Chemistry
• Year: 1998
• Tongue: English
• Weight: 649 KB
• Volume: 35
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570350303

✦ Synopsis

Abstract

The conjugate additions of N‐(α,β‐unsaturated)acylpyrazoles were carried out by the treatment with Grignard reagents in the presence of cuprous halides. The reaction of 2‐(α,β‐unsaturated)acyl‐3‐phenyl‐l‐menthopyrazoles 3a‐h occurred in higher chemical yields and with asymmetric inductions on β‐position, where the addition of magnesium bromide as a Lewis acid influenced to the yields and the diastereoselectivities. In the case of α‐methylated 2‐(α,β‐unsaturated)acyl‐3‐phenyl‐l‐menthopyrazoles 3i‐n, the excellent asymmetric induction on the α‐position was also observed through the diastereofacial protonation.