Reductive Cleavage of Thioethers

Written by Dr Will Watson on Monday, 16 April 2012. Posted in Process Chemistry News

Thiourea is often the reagent of choice for synthesising pyrimidines.  If a sulphur free pyrimidine is required the sulphur needs to be removed oxidatively or reductively.

Reduction is typically carried out using Raney Nickel.  A new reduction method has recently been published by chemists at Merck.  In this new method Heterocyclic thioethers are leaved with triethylsilane and palladium on carbon in THF.

thioethers

There are over 30 examples listed in the paper including pyrimidines, pyrazines pyridazines, oxazoles, benzoxazoles and purines and yields for the vast majority of substrates are 80-96%.  Two yields are 60-67% and in one case (an ethylthiopyridazine) the yield is only 30%.  The method tolerates ketone, ester, amine, and cyclopropylamino groups as well as alkyl groups, benzyl groups and methoxy substituents.

T.H. Graham, W. Liu, and D.M. Shen, Org. Lett., 2011, 13, 6232-6235.

About the Author

Dr Will Watson

Dr Will Watson

Will Watson gained his PhD in Organic Chemistry from the University of Leeds in 1980. He joined the BP Research Centre at Sunbury-on-Thames and spent five and a half years working as a research chemist on a variety of topics including catalytic dewaxing, residue upgrading, synthesis of novel oxygenates for use as gasoline supplements, surfactants for use as gasoline detergent additives and non-linear optical compounds. In 1986 he joined Lancaster Synthesis and during the next 7 years he was responsible for laboratory scale production and process research and development to support Lancaster’s catalogue, semi-bulk and custom synthesis businesses. In 1993 he was appointed to the position of Technical Director, responsible for all Production (Laboratory and Pilot Plant scale), Process Research and Development, Engineering and Quality Control. He helped set up and run the Lancaster Laboratories near Chennai, India and had technical responsibility for the former PCR laboratories at Gainesville, Florida. He joined Scientific Update as Technical Director in May 2000. He is also involved in an advisory capacity in setting up conferences and in the running of the events. He is active in the consultancy side of the business and sits on the Scientific Advisory Boards of various companies.

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