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

[1] New pyrazole alkaloids from the root bark of Newbouldia laevis [J].

Aladesanmi, AJ ;

Nia, R ;

Nahrstedt, A .

PLANTA MEDICA, 1998, 64 (01) :90-91

[2]

ALADESANMI SA, 1995, PHYTOCHEMISTRY, V35, P1053

[3] Bu3SnH mediated oxidative radical cyclisation onto imidazoles and pyrroles [J].

Aldabbagh, F ;

Bowman, WR ;

Mann, E ;

Slawin, AMZ .

TETRAHEDRON, 1999, 55 (26) :8111-8128

[4] Oxidative radical cyclisations onto imidazoles and pyrroles using Bu3SnH [J].

Aldabbagh, F ;

Bowman, WR ;

Mann, E .

TETRAHEDRON LETTERS, 1997, 38 (45) :7937-7940

[5] Acyl radical cyclisation onto pyrroles [J].

Allin, SM ;

Barton, WRS ;

Bowman, WR ;

McInally, T .

TETRAHEDRON LETTERS, 2001, 42 (44) :7887-7890

[6] New cascade 2-indolylacyl radical addition-cyclization reactions [J].

Bennasar, ML ;

Roca, T ;

Griera, R ;

Bosch, J .

JOURNAL OF ORGANIC CHEMISTRY, 2001, 66 (22) :7547-7551

[7] Cascade radical synthesis of heteroarenes via iminyl radicals [J].

Bowman, WR ;

Bridge, CF ;

Brookes, P ;

Cloonan, MO ;

Leach, DC .

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1, 2002, (01) :58-68

[8] Synthesis of heterocycles by radical cyclisation [J].

Bowman, WR ;

Cloonan, MO ;

Krintel, SL .

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1, 2001, (22) :2885-2902

[9] Bu3SnH mediated oxidative radical cyclisations:: synthesis of 6H-benzo[c]chromen-6-ones [J].

Bowman, WR ;

Mann, E ;

Parr, J .

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1, 2000, (17) :2991-2999

[10] Synthesis of heterocycles by radical cyclisation [J].

Bowman, WR ;

Bridge, CF ;

Brookes, P .

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1, 2000, (01) :1-14

← 1 2 3 →