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Please login or sign up for a free trial to access the full content. Variation 5: Copper-Catalyzed Addition of Diboron Reagents to Alkynes

DOI: 10.1055/sos-SD-106-00088

Vaultier, M.; Pucheault, M.Science of Synthesis Knowledge Updates, (20124308.

Nucleophilic borylcopper species, prepared by treating bis(pinacolato)diboron with copper(I) chloride and potassium acetate in dimethylformamide, undergo addition to alkynes to give the corresponding alkenylboronates.[‌20‌] This method can be extended to provide an efficient synthesis of β-borylated α,β-alkenic esters 32 from α,β-acetylenic esters 31 by using a copper–phosphine catalyst based on ligand 30 (Xantphos) (Scheme 13).[‌21‌] The product of syn-addition to the triple bond is obtained almost exclusively, except in the case of the β-tert-butyl-substituted ester 31 (R1 = t-Bu).

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