A Humdinger of a Staudinger

A Humdinger of a Staudinger

Author: Kevin Jones

Brandon Ashfeld and co-workers, University of Notre Dame, USA, have recently reported a new method for the formation of amides. Their strategy involves the use of a chlorophosphite reagent to simultaneously activate a carboxylic acid and an azide which promotes a “traceless Staudinger ligation” (see scheme).

Traceless Staudinger ligation

This transformation boasts two key-features:

  • As the key acyl substitution step is intramolecular, occurring after formation of intermediate A, the reaction can be performed in the presence of other electrophilic or nucleophilic functional groups.
  • Reaction byproducts and unreacted starting material can be conveniently separated from the product by aqueous work-up. Anyone who has ever struggled to remove trace amounts of ureas from carbodiimide promoted coupling reactions will certainly appreciate this added bonus.

In a follow up publication, the team demonstrates how the transformation can also be achieved using catalytic triphenylphosphine and a stoichiometric amount of a silane reductant. The team also demonstrated examples of the reaction’s application in lactam and peptide bond formation, making this a highly useful synthetic reaction.

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