Radical cyclisation onto pyrazoles: synthesis of withasomnine

被引：56

作者：

Allin, SM ^{[1
]}

Barton, WRS

Bowman, WR

McInally, T

机构：

[1] Univ Loughborough, Dept Chem, Loughborough LE11 3TU, Leics, England

[2] AstraZeneca R&D Charnwood, Loughborough LE11 5RH, Leics, England

来源：

TETRAHEDRON LETTERS | 2002年 / 43卷 / 23期

基金：

英国工程与自然科学研究理事会;

关键词：

radical cyclisation; pyrazoles; withasomnine; tributyltin hydride; 1,2-b]-fused bicyclic pyrazoles;

D O I：

10.1016/S0040-4039(02)00763-3

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

A novel synthetic protocol for the synthesis of [1,2-b]-fused bicyclic pyrazoles has been developed using radical cyclisation. The protocol uses cyclisation of pyrazole-1-(omega-alkyl) radicals generated from 1-[omega-(phenylselenyl)alkyl]-pyrazole precursors. The pyrazole natural product, withasomnine (3-phenyl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole), and larger ring analogues have been synthesised in good yield using the protocol. A Bu3SnH-mediated oxidative cyclisation mechanism is facilitated by azo or Et3B radical initiators acting as oxidants of the intermediate pi-radicals. (C) 2002 Elsevier Science Ltd. All rights reserved.

引用

页码：4191 / 4193

页数：3

共 25 条

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