Metal-Free, One-Pot Oxidative Conversion of Aldehydes to Primary Thioamides in Aqueous Media

Abstract

One-pot tandem reactions of a variety of aldehydes with aqueous ammonia, molecular iodine, and O,O-diethyl dithiophosphoric acid readily afford the corresponding primary thioamides. This is an inexpensive, practical, and metal-free way of accessing various thioamides from aldehydes in aqueous media. The pure products are obtained simply by filtration followed by successive washing with aqueous sodium thiosulfate and water.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

GRAPHICAL ABSTRACT

Keywords:

• Aldehydes
• deoxygenation
• green chemistry
• nitriles
• O,O-diethyl dithiophosphopric acid
• thioamides

ACKNOWLEDGMENTS

We sincerely thank the SAIF, Punjab University, Chandigarh, for providing spectra. V. P. S. is grateful to the Department of Science and Technology (DST), Goverment of India, for the award of a Department of Science and Technology–Inspire Faculty position (Ref. IFA-11CH-08) and financial support, and A. K. Y. is grateful to the Council of Scientific and Industrial Research, New Delhi, for the award of a junior research fellowship.

Notes

^a Reaction conditions: 1a (1.5 mmol), I₂ (1.6 mmol), 10 mL of 28% aq. NH₃, and O,O-diethyl dithiophosphoric acid (2) (1.5 mL).

^b Temperature for step (ii).

^c Time for step (ii).

^d Conversion (%) of benzaldehyde (1a) as determined by GC analysis.

^e Selectivity (%) for thioamide 3a; the other side product was benzamide.

^f Yield of isolated and purifide product 3a.

^a For general procedure, see Experimental.

^b All the products are known compounds and were characterized by comparison of their mp and spectral data with those reported in the literature (Table 3). ^{[ 12 , 19j , 21 , 25 ]}

^c Conversion (%) as determined by GC analysis.

^d Selectivity (%) for thioamide 3; the other side product was the corresponding amide.

^e Yield of isolated and purified product 3..