An unexpected Michael type addition-deacylpyrazole involving coumarin-3-formylpyrazoles under mild conditions

Abstract

The first Michael type addition-deacylpyrazole involving α,β-unsaturated pyrazolamides was accomplished by utilizing DMAP as catalyst in mild condition. The protocol enables the access to various oxindole-substituted dihydrocoumarins from coumarin-3-formylpyrazoles and 3-acetoxy oxindoles in excellent yields (up to 99 % yield) with acceptable diastereoselectivities (up to >95:5 dr). In this work, the acylpyrazole group of coumarin-3-formylpyrazoles acted as a temporary activating group for the first time. Detailed mechanistic studies were performed with high resolution mass spectrometry (HRMS) analysis.