Formation of the Sn—Boron Bond

Treatment of l,10-distannacyclodeca-2,8,ll,17-tetrayne 100 with electrophiles leads to cleavage of the Sn-C bonds. The reaction of 100 with three different boron halides giving rise to the formation of acetylene derivatives 286 is summarized in Scheme 48 <1997MGM573>. 

The reaction of an allylmetal derivative of group IV (M = Si, Sn or Ge) with aromatic substrates in the presence of the complex iodosylbenzene-boron trifluoride-diethyl ether results in carbon-carbon bond formation realizing the allylation of the aromatic substrate in generally good yields.236,237... 

The reaction of alkenyl epoxides with organometallic species (lithium, magnesium, copper, and boron) affords allylic alcohols, following an Sn and/or Sn mechanism. These processes can accommodate only little organic functionality and exhibit low regio- and/or stereoselectivity. Under smooth conditions, C—C bond formation proceeds by nucleophilic alkylation of vinyl epoxides in the presence of catalytic amounts of zerovalent palladium. Regio- and stereoselectivity can be achieved via the formation of a Tr-allylpal-ladium complex. Trost and Molander and Tsuji and co-workers simultaneously reported the first studies in 1981. Since then, numerous papers have dealt with this subject. Essentially, after chelation and oxidative addition of the palladium onto the vinyl epoxide, the zwitterionic 7r-allylpalladium complex deprotonates the nucleophile, which can in principle attack either carbon 2 (proximal attack) or 4 (distal attack) (Scheme 1). 

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