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6.1.38.14.3 Variation 3: Oxidation to Aldehydes and Ketones

DOI: 10.1055/sos-SD-006-00903

Zaidlewicz, M.; Krzeminski, M.Science of Synthesis, (200561144.

The oxidation of trialkylboranes containing primary alkyl groups with pyridinium chlorochromate in dichloromethane proceeds to the corresponding aldehydes 56; productivity is generally good and, for example, octanal [56, R1=(CH2)5Me] can be obtained in 71% yield.[‌326‌] It should be noted that the starting trialkylboranes derived from monosubstituted terminal alkenes by hydroboration with borane contain isomers bearing secondary alkyl groups. This arises because there is only 47:3 regioselectivity in the addition reactions. These groups are transformed to the corresponding ketones, contaminating the aldehydes. This inconvenience can be circumvented by the use of more regioselective bis(1,2-dimethylpropyl)borane or monochloroborane instead of borane (Scheme 94).[‌326‌]

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