Domino syntheses of five-, six- and seven-membered O-, N- and S-heterocycles from α-, β- and γ-substituted carboxylic esters

Abstract

By a one-pot procedure, tetronic acids, tetronates, coumarins, benzoxepinones and their N- and S-analogues are readily accessible from keteneylidene(triphenyl)phosphorane 2 and carboxylic esters bearing OH, NHR or SH groups in an α-, β- or γ-position by an addition/Wittig olefination/(Claisen rearrangement) sequence. This cascade can be controlled by temperature variation. Extension of this procedure by a further addition step yielding annulated bisheterocycles such as the furoquinolone 28 is possible in some cases.