The reactions of propargyl amides, ureas, carbamates, and carbonates with B(C 6 F 5 ) 3 proceed via an intramolecular 5-exo-dig cyclization across the alkyne unit to yield the corresponding vinyl borate species. The generated sp 2 carbocation is stabilized by the flanking heteroatoms, allowing for isolation of oxazoline intermediates. The fate of these intermediates is strongly dependent upon the propargylfunctionalized starting material, with the carbamates and carbonates undergoing a ring-opening mechanism (propargyl rearrangement) to give cyclic allylboron compounds, while prolonged heating of the urea derivatives shows evidence of oxazole formation. In a deviation away from the reactivity of carbamates stated previously, the benzyl carbamate substrate undergoes dealkylation at the benzylic position, liberating 5-methyloxazol-2-(3H)-one.

A diverse range of Lewis acidic alkyl, vinyl and aryl boranes and borenium compounds that are capable of new carbon-carbon bond formation through selective migratory group transfer have been synthesised. Utilising a series of heteroleptic boranes [PhB(C6 F5 )2 (1), PhCH2 CH2 B(C6 F5 )2 (2), and E-B(C6 F5 )2 (C6 F5 )C=C(I)R (R=Ph 3 a, nBu 3 b)] and borenium cations [phenylquinolatoborenium cation ([QOBPh][AlCl4 ], 4)], it has been shown that these boron-based compounds are capable of producing novel allyl- boron and boronium compounds through complex rearrangement reactions with various propargyl esters and carbamates. These reactions yield highly functionalised, synthetically useful boron substituted organic compounds with substantial molecular complexity in a one-pot reaction.