Synthesis of Symmetrical Ketones from Organoboranes and 4,4-Dimethyl-2-oxazoline

Abstract

Organoboranes readily obtainable by the hydroboration of alkenes have been recently recognized as highly valuable reagents and intermediates for the synthesis of organic compounds with various functional groups.¹ However, until most recently, there have been no successful reports on the direct synthesis of carboxylic acids from organoboranes.² Since 1967, we have made continuous efforts to discover such a conversion, as one of which we examined the reaction of organoboranes with the lithium salt of 4,4-dimethyl-2-oxazoline followed by treatment with methyl iodide and alkaline hydrogen peroxide, based on the following working hypothesis. Organoboranes may react with the lithium salt of 4,4-dimethyl-2-oxazoline³ to yield the organoborate (I), which are then treated with methyliodide to afford the boron derivatives (11). Finally the organoboranes (11) are changed to the corresponding carboxylic acids by the usual a1kaline hydrogen peroxideoxidation and subsequent acidification (Eq. 1). The actually 05 tained products, however, were not the expected carboxylic acids, and we found that symmetrical ketones are prepared in moderate yiels, when organoboranes with primary alkyl groups are used.