Diastereodivergent formal [4 + 1] cycloaddition of azoalkenes as one-carbon synthons

Abstract

The first diastereodivergent formal [4 ​+ ​1] cycloaddition reactions of azoalkenes with p-quinone methides (p-QMs) have been accomplished. The reported reaction occurred via a domino oxa-1,4-addition/1,6-addition process, allowing the use of common azoalkenes as C1 synthons. A broad range of 2,3-dihydrobenzofurans was smoothly prepared in good yields and with reversible diastereoselectivities. The steric hindrance and hydrogen-bonding interaction were proposed to account for the two different modes of diastereo-control. The projected reaction features the employment of azoalkene as carbene-like C1 synthon, mild conditions, broad substrate scope and tunable diastereoselectivity.

Keywords

• Azoalkene
• One-carbon synthon
• Diastereodivergent
• [4 + 1] Cycloaddition
• para-Quinone methides