Alkenylboronic acids, Michael

Scheme 4.36 Enantioselective Michael addition of alkenylboronic acids and alke-nylboronates to enones.

Scheme 19.29 Enantioselective Michael addition of a, B-unsaturated ketones with alkenylboronic acids catalysed by thiourea 22.

J. Michael Chong of the University of Waterloo has found (J. Am. Chem. Soc. 2007, 129, 4908) that the Binol-mediated enantioselective conjugate addition of alkenylboronic acids such as 22 required the additional activation of the aryl ketone. Shun-Jun Li of... 

Rhodium(i) complexes are excellent catalysts for the 1,4-addition of aryl- or 1-alkenylboron, -silicon, and -tin compounds to a,/3-unsaturated carbonyl compounds. In contrast, there are few reports on the palladium(n) complex-catalyzed 1,4-addition to enones126,126a for the easy formation of C-bound enolate, which will result in /3-hydride elimination product of Heck reaction. Previously, Cacchi et al. described the palladium(n)-catalyzed Michael addition of ArHgCl or SnAr4 to enones in acidic water.127 Recently, Miyaura and co-workers reported the 1,4-addition of arylboronic acids and boroxines to a,/3-unsaturated carbonyl compounds. A cationic palladium(n) complex [Pd(dppe)(PhCN)2](SbF6)2 was found to be an excellent catalyst for this reaction (dppe = l,2-bis(diphenyl-phosphine)ethane Scheme 42).128... 

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