Dialkenylgermanes as Precursors of Silsesquioxane‐based Macromolecular Structures

Herein we report a study of highly efficient platinum‐catalyzed hydrosilylation of dialkenylgermanes with silsesquioxanes and spherosilicates. The use of divinyl‐ and diallylgermanes allowed the synthesis of new classes of compounds, i. e., dumbbell‐type systems, silsesquioxanes with alkenyl pendant group, and oligomeric derivatives. The results are supported by detailed data from in situ FT‐IR and NMR measurements, enabling precise monitoring of the reaction progress and determination of regioselectivity of the formed products.     

Remote stereocontrol using functionalized allylmetal reagents

Alk-2-enyl(trialkyl)stannanes with heteroatom substituents at the 4-, 5-, and 6-positions are transmetallated stereoselectively using tin(IV) halides to generate allyltin trihalides, which react with aldehydes to give (3Z)-homoallylic alcohols with efficient 1,5-, 1,6-, and 1,7-stereocontrol. This chemistry has been used to develop new strategies for natural product synthesis. Because of the toxicity of organotin reagents and the problems in removing organotin residues from reaction products, alternative procedures that avoid the use of organotin reagents have been investigated. To date, alk-2-enylgermanium reagents have been shown to deliver effective 1,5- and 1,6-stereocontrol, which is analogous to that observed for the organotin compounds. Organobismuth intermediates, which can be generated from allyl bromides and zinc-bismuth(III)iodide, react with aldehydes with efficient 1,5-stereocontrol which is complementary to that observed with the organo-stannanes or -germanes in that (3E)-homoallylic alcohols are obtained.