The subtle co-catalytic intervention of benzophenone in radical cation mediated cyclization - an improved synthesis of 2-(3 ',4 '-Dimethoxyphenyl) indoline
Document Type
Article
Publication Date
1-22-2008
Abstract
The addition of benzophenone to a FeCl(3)/CH(2)Cl(2) mixture in the presence of 3',4'-dimethoxy-2-acetamidostilbene 17 unexpectedly leads to a dramatic improvement in yield of the indoline 20 from 38% (previously reported by us) to 75.4%, after careful examination of a variety of reaction conditions. A catalytic cycle has been proposed that involves not only stilbene radical cations but also Fe(2+) promoted benzophenone ketyl radical formation which enhances cyclisation, suppresses dimerization and accounts for the virtually quantitative recovery of the benzophenone.
Keywords
radical cation, benzophenone, ketyl radical, maleic anhydride, oxidative cyclization, fecl3-promoted synthesis, alkaloids, derivatives, construction, dimerization, duocarmycins, cc-1065
Divisions
CHEMISTRY
Publication Title
Heterocycles
Volume
75
Issue
5
Additional Information
Department of Chemistry, Faculty of Science Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA