Oxidative radical cyclization on enamide systems using n-Bu3SnH and dilauroyl peroxide
作者:Miguel A. Guerrero、Raymundo Cruz-Almanza、Luis D. Miranda
DOI:10.1016/s0040-4020(03)00764-6
日期:2003.6
Efficient 5-endo and 6-endo oxidative radical cyclizations on enamide systems are described using nBu(3)SnH and dilauroyl peroxide both as initiator and oxidant. Dibenzoyl peroxide and dicumyl peroxide were also tested in the same reaction and the product yields were very similar to those obtained with dilauroyl peroxide. The erythrina ring system was constructed in a two-step sequence featuring this novel process. (C) 2003 Elsevier Science Ltd. All rights reserved.
Is an Iodine Atom Almighty as a Leaving Group for Bu<sub>3</sub>SnH-Mediated Radical Cyclization? The Effect of a Halogen Atom on the 5-Endo-trig Radical Cyclization of <i>N</i>-Vinyl-α-halo Amides
The effect of a halogen atom as a leaving group on Bu3SnH-mediated 5-endo-trig radical cyclization of N-(cyclohex-l-enyl) alpha-halo amides was examined. The cyclization of alpha-chloro amides occurred with a high degree of efficiency, whereas the corresponding alpha-iodo congeners gave only limited quantities of cyclization products. A detailed study revealed that these phenomena could be attributed to the initial conformations of alpha-halo amides. The cyclizing ability of alpha-iodo amides can be restored with Bu3SnCl or Bu3SnF as an additive. The cyclization of an alpha-iodo amide in the presence of Bu3SnF could be applied to a short-step synthesis of lycoranes featuring sequential 5-endo-trig and 6-endo-trig radical cyclizations.