Synthesis of carbamates by direct C-H bond activation of formamides

Copper catalysed oxidative coupling reaction of formamides with β-keto esters and 2-carbonyl-substituted phenols successfully proceeded through direct C-H bond activation of formamides. The corresponding carbamates were formed with high stereoselectivity under mild reaction conditions. This protocol was successfully applied to the synthesis of three novel halogenated carbamates and a carbaryl insecticide derivative. Our results suggest the use of 6.0 equiv. TBHP is crucial for this type of reaction. Synthesis of carbamates was accomplished through the reaction of β-keto esters or 2-carbonyl- substituted phenols with formamides using copper chloride and an oxidant. Sixteen aliphatic as well as fourteen aromatic carbamates were prepared in good to excellent yields. The methodology was applied to the synthesis of halogenated carbamates and a carbaryl insecticide derivative. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.