C-H amination reactions inside α-cyclodextrin supramolecular capsule

Abstract

We describe the photochemical generation of an alkoxycarbonylnitrene species in a supramolecular capsule and its reactivity. 2-Adamantyl-carbonazidate was co-crystallized in a supramolecular capsule consisting of two alpha-cyclodextrins (α-CDs) interacting through a hydrogen bond network. Irradiation of the co-crystal with UV light (254 nm) in the solid state or in suspension resulted in the extrusion of a nitrogen molecule and the corresponding nitrene formation inside the capsule. This reactive species provides selective C-H amination of the capsule wall, specifically at carbon 5 of the α-CD unit. The supramolecular assembly fixes the geometry of both reactants, the nitrene and the C-H bond, in line, mimicking the transition state for the triplet nitrene H-atom-abstraction reaction. Enantioselective intramolecular formation of a minor product, a carbamate, occurring concomitantly in the CD capsule, helps clarify the mechanisms of C-H amination reactions.