SONOCHEMICAL INITIATION OF RADICAL-CHAIN REACTIONS - HYDROSTANNATION AND HYDROXYSTANNATION OF C-C MULTIPLE BONDS

Irradiation of R(3)SnH with ultrasound generates tin radicals in the region of hot sonochemical cavities, which then undergo useful synthetic reactions in the bulk liquid phase. Thus, ultrasound irradiation of a mixture of a tin hydride and an alkyne produces vinylstannanes at temperatures as low as -50 degrees C, and the reactions under irradiation have been found to proceed >100 times faster than those without it. Hydrostannation of electron-deficient olefins also proceeds at low temperatures. Ultrasound-promoted radical reaction of an organotin hydride reagent to an activated olefin in the presence of air results in the addition of stannyl and hydroxyl groups across the C-C double bond (hydroxystannation). The reaction of dienes may proceed either in a 1,2- or 1,4-manner to provide beta-hydroxy stannanes or hydroxylated allylic stannanes, respectively. Instead of using a tin hydride reagent, the use of a mixture of a tin chloride reagent and NaBH4 as an in situ source of a tin hydride reagent made an experimentally convenient method for the hydroxystannation reaction.