Alkylation of amines with allylic alcohols and deep eutectic solvents as metal-free and green catalyst

A novel approach for the allylic alkylation of anilines, hydrazides and indole derivatives by the direct use of allylic alcohols is described under very mild conditions, such as room temperature and using sustainable deep eutectic solvents (DESs). The search of the optimum DES to be used in the reaction reveals that a simple mixture of choline chloride (ChCl) and lactic acid provides excellent results for a wide substrate scope and with high isolated yields. This methodology represents a great improvement compared to other procedures described in literature, for which high temperatures, stronger reaction conditions or metal catalysts are usually required. In some cases, this protocol affords to the first examples of trapping allylic carbocations with indole derivatives. All these features make this procedure an appealing and green alternative in comparison with other examples reported in literature on alkylation of amines by allylic alcohols. Preliminary mechanistic studies using unsymmetrically substituted alcohols support that the reaction should proceed by an SN1 pathway.Introduction.