An efficient synthesis of 4-isochromanones via Parham-type cyclization with Weinreb amide

The synthesis of 4-isochromanones via Parham-type cyclization with Weinreb amide as the internal electrophilic group, t-BuLi as the lithium reagent was described. The reaction was efficient and could be completed in one minute. The application scope of this new protocol was investigated and the desired products could be obtained in good to excellent yields. Besides, the synthetic potential of this method was further demonstrated by the synthesis of natural product (±)-XJP, which was obtained in six steps with overall yield up to 54%.

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