Stannylboration alkynes

The stannylboration of alkynes was followed by cross-coupling of the G-Sn bond in the synthesis of stereodefined 1-alkenylboron compounds 143 (Equation (48)).261 There was a large accelerating effect of boryl substituents on thermal ring closing to the methylene cyclobutenes at 140 °G. 

Table 16.4, which is adapted from a comprehensive review by Miyaura from 2001, illustrates the scope and types of catalysts that have been used for the diboration, silylboration, and stannylboration of alkynes. These data illustrate that the simple platinum(O) complex of PPhj is a suitable catalyst for diboration. ° - ° These data also show that both B rin and BjCat add to terminal alkynes, but that the tetraaminodiboron reagent does not. Finally, these data illustrate that palladium complexes of isonitrile ligands catalyze the silylboration of alkynes and that simple Pd(PPhj) catalyzes the stannylboration of terminal alkynes. ... 

The diborations of alkenes and alkynes are thought to occur by the general pathway shown in Scheme 16.15 and analogous silylborations and stannylborations would occur by related mechanisms. By this mechanism, the oxidative addition of the diborane(4), silylborane, or stannylborane reagent leads to a bisboryl, a silylboryl, or a stannylboryl complex. These oxidative addition processes are described in Chapter 6. In brief, Miyaura and Ishiyama, Marder, and Smith all published examples of the oxidative addition of diboron compounds to and Marder has published examples of the oxidative... 

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