Silaborative dimerization

Silaborative dimerization of two molecules of internal alkynes in the presence of a silylborate is catalyzed by Ni(0) generated in situ [155],... 

The same type of bis-functionalization has been reported for the palladium-catalyzed borylstannylative carbocy-cyclization of 1,6-, 1,5-, 1,7-diynes, bis-propargylamine, and ether.377 It should be noted that even 1,2-dialkylidene cyclobutane can be obtained in reasonable yield. Ito has proposed the related silaborative reaction involving nickel(O) catalysis.378 This reaction has been performed in an intra- and intermolecular fashion. The intramolecular reaction allows the formation of cyclic dienes and the intermolecular process proceeds through a dimerization of alkynes to give acyclic dienes. 

Suginome et al. discovered that the use of Ni(acac)2 and DIBAL-H as a reductant results in the double insertion of alkynes 280 across the B-Si bond in silaborane 281 to afford silaborated butadienes 282-284 (acac = acetylaceto-nate). NMR experiments revealed the stereoselective formation of head-to-head dimerization product 282 as the... 

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