Sonolysis of hydrogen-element bonds

The cleavage of the phosphorus-hydrogen and tin-hydrogen bonds was reported with interesting synthetic applications. For the sake of comparison with the cases discussed above, the energies of the P-H and Sn-H bonds are in the range of 310-320 kJmoH. 

Conventionally, the addition of tin hydrides to unsaturated C-C bonds requires the thermal homolytic cleavage of the Sn-H bond, most of the time in the presence of a radical initiator. Important papers dedicated to the sonochemical version of this reaction were published by Nakamura et In the intro- 

69 Pereyre, M. Quintard, J.P. Rahm, A. Tin in Organic Synthesis Butterworth, London, 1987. 

After initiation, the RaSn radical adds to alkenes and alkynes (Fig. 19). Reactions run at different temperatures indicate that this addition occurs in the bulk solution. 

Excellent results are obtained in the absence of an initiator, even at temperatures unusually low for this type of reaction. Without sonication, the conversion is poor. The reaction can be run with a probe generator, but it remains effective when a bath is used. Sonochemical conditions greatly enhance the stereoselectivity, probably because of the temperature factor. For example, hexyne gives the triphenylstannyl olefin in 93% cis selectivity. By photolysis, a 1 1 cis trans mixture is obtained. 

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