Synthesis of photochromic thieno-2H-chromene derivatives

摘要

Syntheses of photochromic thieno-2H-chromenes from hydroxybenzo[b]thiophenes and 1,l-diphenyl-2-propyn-l-ol ~e an acid catalyst are described. The hydroxybenzo[b]thiophenes were prepared by demethylation of meth-~‘vbenzo[b]thiophenes with pyridinium chloride or boron tribromide. The precursors were synthesized in two steps, iich involved the reaction of methoxythiophenols with 3-broinobutan-2-one in an alkaline medium, to give ketoar-~jifides. followed by cyclization using phosphorus pentoxide or polyphosphoric acid. The photochromic behaviour the target compounds was evaluated with the aid of the usual spectrokinetic parameters, and the results were cam-red to data from reference compounds that are benzoannellated in the 5,6 and 7,8 positions of the 2H-chromene system.