Unexpected One-Pot Synthesis of 3-Cinnamoyl-3-hydroxyphthalide Derivatives

A new and simple method to prepare 3-cinnamoyl-3-hy-droxyphthalide derivatives from 2-hydroxy-3-methyl-1,4-naphthoqui-none and substituted benzaldehydes was unexpectedly uncovered. There action was conveniently performed in DMSO at 100 degrees C with K3PO4 as a base and AlCl3 as a catalyst. We propose that the reaction proceeds bya cascade process involving nucleophilic addition followed by demethylation and rearrangement. The products were typically obtained in moderate to good yields. The highest yield (95%) was obtained when the reaction of 2-bromobenzaldehyde was performed for 24 hours. X-ray crystallography of the product derived from 2-fluorobenzaldehydeunequivocally confirmed the structure of the hydroxyphthalide derivatives