Efficient one-pot preparation of bis(pyrazino[2′,3′:4,5]thieno[3,2- d]pyrimidin-4-yl)benzenes based on an aza–Wittig/mediated annulation strategy

Abstract

Aza–Wittig mediated annulation provides a highly facile and straightforward one-pot strategy for the synthesis of bis(pyrazino[2′,3′:4,5]thieno[3,2- d]pyrimidin-4-yl)benzenes 5 and 7. A tandem aza–Wittig reaction of iminophosphorane 2 with 1,4- or 1,3-phenylene diisocyanate, followed by intramolecular heteroconjugate addition annulation after addition of a nucleophilic reagent (amine, phenol, thiophenol or ROH), in presence of catalytic K 2CO 3 or NaOR, gives selectively the functionalized bis(pyrazinothienopyrimidinones) 5 and 7.