Synthesis of p-phenylthio- peri-hydroxy polyaromatic compounds by strong-base-induced [4+2] cycloaddition of 4(phenylthio)homophthalic anhydrides with phenylsulfinyl-dienophiles

A direct and regioselective synthesis of p-phenylthio-substituted peri-hydroxy polyaromatic compounds (9-12) was developed via the strong-base-induced [4+2] cycloaddition of the 4-(phenylthio) homophthalic anhydrides (1a-d) to the phenylsulfinyl-substituted dienophiles (5-8). The sulfinyl group in 5-8 is the key to producing the desired reaction under mild conditions (at 20 degreesC to room temperature) in good yields. A reaction mechanism explaining the remarkable effect of the sulfinyl group is discussed.