New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4 H -3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence.

A new efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4 H -3,1-benzothiazines via sequential Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution reaction has been developed. The three-component Passerini reactions of 2-azidobenzaldehydes 1 , benzoic acid ( 2 ), and isocyanides 3 produced the azide intermediates 4 , which were treated sequentially with triphenylphosphine, isocyanates (or CS 2 ), and secondary amines to give polysubstituted 3,4-dihydroquinazolines 8 and 4 H -3,1-benzothiazines 11 in good overall yields through consecutive Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution reactions.