Highly Diastereoselective Preparation of Tertiary Alkyl Isonitriles by Stereoinvertive Nucleophilic Substitution at a Nonclassical Carbocation.

A highly efficient SnCl-catalyzed nucleophilic isocyanation of cyclopropyl ethers has been developed. The reaction proceeds at the quaternary carbon stereocenter of the cyclopropane with a complete inversion of configuration, providing a new avenue for the construction of synthetically challenging tertiary alkyl isonitriles with high diastereopurity. The diversity of the incorporated isocyanide group has been demonstrated by the transformation of tertiary alkyl isonitriles into the corresponding tertiary alkyl amines, amides, and cyclic ketoimines.