Oxidative radical cyclization to pyrroles under reducing conditions. Reductive desulfonylation of α-sulfonylpyrroles with tri-n-butyltin hydride
作者:
Yulia Antonio,
Ma. Elizabeth De La Cruz,
Edvige Galeazzi,
Angel Guzman,
Brian L. Bray,
Robert Greenhouse,
Lilia J. Kurz,
David A. Lustig,
Michael L. Maddox,
Joseph M. Muchowski,
期刊:
Canadian Journal of Chemistry
(NRC Available online 1994)
卷期:
Volume 72,
issue 1
页码: 15-22
ISSN:0008-4042
年代: 1994
DOI:10.1139/v94-004
出版商: NRC Research Press
数据来源: NRC
摘要:
1-(2-Bromobenzyl)-2-alkanesulfonylpyrroles (1c,1d) and 1-(4-bromobutyl)-2-methylsulfonfylpyrrols (8) undergo oxidative radical cyclization with partial or complete reductive desulfonylation to the pyrrolizidine derivatives5and9by an AIBN initiated reaction with tri-n-butyltin hydride. These cyclizations are suggested to proceed via a pseudo SRN1 process involving radical addition to the α position of the pyrrole nucleus not bearing the sulfonyl group. Reductive removal of the alkylsulfonyl moiety is proposed to occur in a second process after completion of the oxidative radical cyclization. The site of the radical addition is supported by deuterium labelling studies. Consistent with the timing of the loss of the sulonyl group is that 2-alkysulfonylpyrroles11are reductively desulfonylated under the same conditions that effect the oxidative radical cyclizations.
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