Copper-Catalyzed Reductive Ireland-Claisen Rearrangements of Propargylic Acrylates and Allylic Allenoates.

Siyuan Guo, Kong Ching Wong, Stephan Scheeff, Zhuo He, Wesley Ting Kwok Chan, Kam-Hung Low, Pauline Chiu

The Journal of organic chemistry 2022 Jan 07

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The copper-catalyzed reductive Ireland-Claisen rearrangement of propargylic acrylates led to 3,4-allenoic acids. The use of silanes or pinacolborane as stoichiometric reducing agents and triethylphosphite as a ligand facilitated the divergent and complementary selectivity for the synthesis of diastereomeric anti- and syn-rearranged products, respectively. Copper-catalyzed reductive Ireland-Claisen rearrangement of allylic 2,3-allenoates proceeded effectively only when pinacolborane was used as a reductant to generate various 1,5-dienes in excellent yields and with good diastereoselectivities in some cases. Mechanistic studies showed that the silyl and boron enolates, rather than the copper enolate, underwent a stereospecific rearrangement via a chairlike transition state to afford the corresponding Claisen rearrangement products.

Citation

Siyuan Guo, Kong Ching Wong, Stephan Scheeff, Zhuo He, Wesley Ting Kwok Chan, Kam-Hung Low, Pauline Chiu. Copper-Catalyzed Reductive Ireland-Claisen Rearrangements of Propargylic Acrylates and Allylic Allenoates. The Journal of organic chemistry. 2022 Jan 07;87(1):429-452