Stereoselective Synthesis of Allenyl Alcohols by Cobalt(III)‐Catalyzed Sequential C−H Bond Addition to 1,3‐Enynes and Aldehydes

Abstract

An efficient and stereoselective CoIII‐catalyzed sequential C−H bond addition to 1,3‐enynes and aldehydes is disclosed. This transformation represents the first example of sequential C−H bond additions to 1,3‐enynes and a second coupling partner and provides the first example of preparing allenes by C−H bond addition to 1,3‐enynes. A wide range of aldehydes, C−H bond substrates and 1,3‐enynes with large substituents on the alkynes are effective substrates. The allenyl alcohol products can be further converted to dihydrofurans with high stereoselectivity either in situ or under Ag‐mediated cyclization conditions. The allenyl silyl group can also be transferred to the adjacent alcohol by a Brook rearrangement. Moreover, a mechanism for the transformation is proposed supported by X‐ray structural characterization of a cobaltacycle intermediate.