Reaction of TPP-azodicarboxylate zwitterions and aryl aldehydes: unprecedented synthesis of acyl carbamates

A study on the reaction of 3-alkyl(aryl)imidazo[1,5-a]pyridines with ninhydrin

The reaction of 3-alkyl(aryl)imidazo[1,5-a]pyridines (1) with ninhydrin in dichloromethane at room temperature delivered good yields of the respective 2-hydroxy-2-(imidazo[1,5-a]pyridine-1-yl)indene-1,3-diones. In the presence of dimethyl acetylenedicarboxylate (DMAD), this uncatalyzed electrophilic substitution reaction, involving C-1 (in 1) and the central C=O (in ninhydrin), takes precedence over the three-component 1,4-dipolar cycloaddition reaction. This selectivity is probably due to the higher electrophilicity of the carbonyl carbon-2 in ninhydrin as compared to that of the sp-carbon atoms in DMAD, augmented with the high nucleophilicity of carbon-1 in 1.

Copper-catalyzed carbonylation of anilines by diisopropyl azodicarboxylate for the synthesis of carbamates

Herein, a simple Cu-catalyzed system for the synthesis of carbamates has been developed using anilines with diisopropyl azodicarboxylate as a carbonyl source under solvent-free conditions.

Synthesis of acyl carbamates via four component Pd-catalyzed carbonylative coupling of aryl halides, potassium cyanate, and alcohols

A simple and mild method is demonstrated for assembling acyl carbamates through a base-free four-component Pd-catalyzed carbonylation of aryl halides in the presence of potassium cyanate and alcohols in a two-chamber system. This approach produces a wide range of aryl acyl carbamates in good to excellent yields from the corresponding aryl bromides or iodides with near-stoichiometric carbon monoxide. In addition, the method can be extended to the synthesis of primary amides thereby expanding the usefulness of cyanate as an ammonia equivalent.