Small rings in focus: recent routes to cyclopropylgroup containing carbo- and heterocycles

The development of modern synthetic methodologies and advanced analytical tools during almost 130 years after the first preparation of a three-membered carbocycle made it possible that several unusual and initially exotic hydrocarbons with cyclopropane rings have become common laboratory reagents. These hydrocarbons not only exhibit unusual physical and thermochemical properties: as the cyclopropane ring is a functional group itself, all of these molecules and their derivatives constitute oligofunctional building blocks, and they can be involved in transformations of the initially formed intermediates or products in sequential reactions or multistep cascade reactions. In many cases, this results in the formation of carbo- and heterocycles with cyclopropyl substituents on a framework or cyclopropyl groups incorporated in a structure. Some of these products exhibit significant biological activities, the cyclopropyl groups exerting favorable or beneficial effects in a number of senses.