Homologation of Carbonyl Compounds to Aldehydes with Lithium Bis(ethylenedioxyboryl)methide

Article abstract of DOI:10.1021/jo01294a033

Tris(ethylenedioxyboryl)methane reacts with methyllithium at -78 deg C in THF to form lithium bis(ethylenedioxyboryl)methide, which reacts with aldehydes and ketones to form 1-alkene-1-boronic esters.These need not be isolated for efficient oxidation by sodium perborate to the homologated aldehydes, which are easily purified.Systematic investigation of the reaction conditions to optimize yields at each step was undertaken.Possibly hazardous 2:1 aldehyde-hydrogen peroxide adducts were found to form under neutral conditions with dilute (5percent) hydrogen peroxide.Hydrogenperoxide was also found to cause some carbon-carbon bond cleavage during oxidation of alkeneboronic acids.Both problems were avoided by the use of sodium perborate instead.Reaction of lithium bis(ethylenedioxyboryl)methide with benzoyl chloride or methyl benzoate followed by hydrolysis was found to yield acetophenone.A significant error in one previous description of the synthesis of the key starting material, tris(dimethoxyboryl)methane, is noted.