Polymer-Supported Aza-Wittig Reaction

A perfluoroalkyl-tagged triphenylphosphine and aminomethyl polystyrene based solid-phase bound phosphine were applied for the parallel synthesis of 4(3ff)-quinazolinones (2) via the intramolecular aza-Wittig reaction by Bannwarth et al. [169]. Both reagents provide a library of 2 by a simple work-up procedure in good yields. A diverse library of benzodiazepine-quinazolinone alkaloids (the circumdatin family, cf 3.3) has been prepared by Thomas with a polymer supported phosphine-mediated intramolecular aza-Wittig reaction as the key step, a novel modified Eguchi aza-Wittig protocol (Scheme 9) [ 170]. The multi-arrayed library generation strategy starts out from readily accessible benzodiazepinediones 50 and anthranilic acids, and all library members were purified by preparative reversed-phase HPLC, yielding 283 isolated pure products 51a,b and 52a,b from 384 individual reactions.

Scheme 9 Benzodiazepine-quinazoline alkaloids library by polymer supported phosphine-mediated aza-Wittig reaction [170]

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