Selective Reduction of Cyclohexanones with NaBH₄ in β-Cyclodextrin, PEG-400, and Micelles

Abstract

We report about the selective reduction of eight cyclohexanones with NaBH₄ in aqueous solutions of β-cyclodextrin, PEG-400, cationic micelles of CTAB and CPC, anionic micelles of SDS and SS at room temperature and at 80°C. All results were compared with NMR, GC-MS as well as with IR. The charge of the micellar head group influences the preferential direction of hydride attack by favoring one reactant conformation over the other and the outcome is more products with the H⁻  in the axial position. One example is the reduction of ketone 4. It was obtained 73% of trans 4-tert-butylcyclohexanol in CTAB, 90% in SDS and 94% in SS micelles. The importance of this work is in the obtained selectivity, the high yields, and the simplicity.

Keywords:

• Selective ketone reduction
• Cyclohexanones
• Sodium borohydride
• PEG-400
• Beta cyclodextrin
• Micelles

Acknowledgements

This work was supported by a grant number 2.03.01.00.012 from the Research Council of Croatia.