Ricerc@Sapienza

The investigation on tandem addition/cyclization reactions of β-(2-aminophenyl)-α,β-ynones with arylisocyanates/benzoyl isothiocyanate is reported. Experimental results show the suitable conditions to selectively direct the reaction outcome towards the product of 6-exo-dig N-, O-, or S-annulation of the in situ generated alkynyl urea/thiourea intermediate. The reaction of a variety of β-(2-aminophenyl)-α,β-ynones with aryl isocyanates/benzoyl isothiocyanate led to the selective formation of quinazoline orbenzoxazine/benzothiazine derivatives, respectively. Density functional theory calculations provide a plausible rationale for the reaction outcome