Thermolysis of Acylazo <i>O</i>-Trimethylsilyl Cyanohydrins: Azoalkanes Yielding Captodatively Substituted Radicals
作者:Charles F. Billera、Travis B. Dunn、David A. Barry、Paul S. Engel
DOI:10.1021/jo981372h
日期:1998.12.1
A new synthetic method has been developed for preparing azoalkanes bearing geminal ol-cyano and alpha-trimethylsiloxy groups. While the symmetrical compound 5 decomposes near room temperature to afford, almost entirely, the C-C dimers, the unsymmetrical azoalkane 3 requires heating to 75 degrees C. The thermolysis activation parameters of 3 and 5 can be rationalized on steric grounds without invoking captodative radical stabilization. A C-13 NMR product study of photolyzed 3 in the presence of TEMPO at 21 degrees C shows that the fate of caged [tert-butyl, 1-trimethylsiloxy-1-cyanoethyl(14)] radical pairs is disproportionation, 17%, cage recombination, 20%, and cage escape, 63%.