title: Boc-protected 1-(3-oxocycloalkyl)ureas via a one-step Curtius rearrangement: mechanism and scope.
abstract: 1-(3-Oxocyclobutyl) carboxylic acid (4a) was converted intoN-Boc-protected 1-(3-oxocyclobutyl) urea (5a), a key intermediates for the preparation of agonists of metabotropic glutamate receptor 5, in one-step when treated with diphenyl phosphoryl azide and triethylamine intert-butanol. The mechanism of the reaction involves a nucleophilic addition of thein situgeneratedtert-butyl carbamate to the isocyanate intermediate. This reaction is applicable to other 1-(3-oxocycloalkyl) carboxylic acids but not to linearγ-keto carboxylic acids.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201 ; College of Animal Science and Technique, Heilongjiang Bayi Agriculture University, Daqing 163319, Heilongjiang, PR China.
authors.forename: Xianyu
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201.
authors.forename: Rachita
authors.initials: R
authors.lastname: Rai
authors.affiliation: Naval Research Laboratory, Code 6930, 4555 Overlook Ave., Washington, DC 20375.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Deschamps
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Mackerell
authors.affiliation: Department of Anesthesiology, University of Maryland School of Medicine, 20 Penn Street, Baltimore, Maryland 21201.
authors.forename: Alan I
authors.initials: AI
authors.lastname: Faden
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201.
authors.forename: Fengtian
authors.initials: F
authors.lastname: Xue
keywords: 1-(3-Oxo)ureas; 1-(3-Oxocyclobutyl) carboxylic acid; Carbamoylcarbamate; Curtius rearrangement; γ-Keto carboxylic acid