Isoureas: Versatile Alkylation Reagents in Organic Chemistry

Introduction

The name of isoureas (alternatively named pseudoureas) derives from their isomeric relationship to ureas. However, their chemical reactivities are much different to that of ureas. Isoureas are important, sometimes commercial reagents in organic chemistry, mainly being used as alkylation reagents in esterification, etherification and in the synthesis of alkyl halides, etc. Isoureas can be conveniently prepared from alcohol and N,N-dialkyl carbodiimide. In most cases, the alkyl group is cyclohexyl or isopropyl. A typical procedure is as following: a mixture of alcohol, DIC and Cu(OTf)₂/CuCl was stirred for 1 h at room temperature. The progress of the reaction can be monitored by IR spectroscopy by the disappearance of diimide absorption at 2100 cm^-¹ and the appearance of isourea absorption at 1660 cm^-¹. Pure isoureas can be obtained after column chromatography or distillation. [¹]

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