Novel Template Effects of Distannoxane Catalysts in Highly Efficient Transesterification and Esterification

Article abstract of DOI:10.1021/jo00018a019

The transesterification of carboxylic esters and the esterification of carboxylic acids are effected under mild conditions under catalysis by 1,3-disubstituted tetraalkyldistannoxanes 1.Various functional groups remain unaffected and otherwise difficult to obtain esters are accessible.An ester bearing a tertiary butyl group in the carboxylic acid moiety remained unchanged in competition experiments with a less bulky ester, which undergoes transesterification quantitatively.The unique features of the reactions are attributable to the template effects of the dimeric structure of 1.The facility with which compounds 1 can be converted into alkoxystannoxanes 2 and the synergistic effect of the proximate tin atoms of 2 play key roles in permitting smooth reactions and high selectivity.Another notable feature of compounds 1 is their unusually high solubility in organic solvents, even though the compounds have a metaloxane core as a major skeletal part.The double-layered structure of 1, in which the inorganic moiety is surrounded by eight alkyl groups, permits esterification to be driven to completion simply by heating a mixture of the carboxylic acid and the alcohol.The distannoxane-catalyzed esterification is irreversible, and thus, no hydrolysis of the product esters occurs when compounds 1 are used as catalysts.