syn-Selective α-Boration-Arylation of Alkynes: Concise Access to Configurationally Defined Tetrasubstituted Alkenes
Prachi Shah1, Maciej Dajek1, Urszula Klimczak1
1Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
Abstract:
Hydro- and heteroboration of alkynes typically delivers a boron substituent at the β-position. Herein, syn-selective α-borylation-arylation is accomplished through a one-pot Ni-catalyzed carbomagnesiation followed by borylation. The regio- and stereoselectivity is established in the carbometalation step, while utilization of B(pin)H is essential for high efficiency of borylation of the sterically hindered vinylmagnesium intermediate. The resulting trisubstituted vinyl boronates are versatile building blocks, in particular, for the synthesis of configurationally defined tetrasubstituted olefins through cross-coupling. A two-step synthesis of Tamoxifen is presented.
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