Me3SiCl/HMPA accelerated conjugate addition of catalytic copper reagent. Stereoselective synthesis of enol silyl ether of aldehyde
✍ Scribed by Yoshiaki Horiguchi; Satoshi Matsuzawa; Eiichi Nakamura; Isao Kuwajima
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- French
- Weight
- 277 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Copper-catalyzed conjugate addition of the Grignard reagents in the presence of Me3SiCl and HMPA proceeds in much higher yield than the reaction of conventional organocopper reagents and shows very good regio-, stereo-, and chemoselectivities. Conjugate addition of organocopper reagents,' originated from Kharasch's catalytic prototype, 2 undoubtedly ranks among the most important synthetic reactions. lb During the evolutionary course of organocopper chemistry, a belief in the superiority of stoichiometric to catalytic reagents has been cultivated; for the classical catalytic procedure is less reproducible and less selective.lb We wish to report here that the presence of Me3SiCl and hexamethylphosphoric triamide (HMPA) during the catalytic addition reaction removes many of the drawbacks of the classical catalytic procedure, and, more importantly, opens new avenues of selectivities that have not been available even by stoichiometric reagents.3 5 mol% Cu'