Rapid Aqueous Borohydride Reduction of Carbonyls Under Sealed-Tube Microwave Conditions

Abstract

Ketones and aldehydes are conveniently and rapidly reduced to the corresponding alcohols in good yields using sodium borohydride under sealed-tube microwave conditions in either 95% ethanol or water. In purely aqueous systems, highly aliphatic substrates are sluggish, but this can be overcome by introducing sodium dodecyl sulfate (SDS) at the critical micelle concentration. With a 2:1 substrate/borohydride ratio and a reaction temperature of 100 °C, reduction is typically complete within 1 min in 95% ethanol and 5 min in water/SDS. The methodology is well suited for parallel and combinatorial synthetic approaches.

GRAPHICAL ABSTRACT

Keywords:

• Aldehydes
• aqueous
• ketones
• microwave
• sodium borohydride

ACKNOWLEDGMENTS

The authors gratefully acknowledge Allegheny College and the National Science Foundation (CCLI 0837640) for generous support of this project.

Notes

^a Molar ratios of substrate/borohydride are 2:1 for 95% ethanol and 3:2 for aqueous systems.

^b Calculated using ACD/Labs Software v11.02 via SciFinder.

^c 94% after 5 min.

^d 94% after 30 min.

^e 98% after 5 min.

^f 92% after 5 min in tetrahydrofuran.