In situ NMR spectroscopic studies of aniline ortho acylation (“sugasawa reaction”): The nature of reaction intermediates and Lewis acid influence on yield

Ortho acylation of anilines by nitriles in the presence of BCl3 and a second Lewis acid appear to proceed through an intermediate "supercomplex" including all four components. Yield improvements were obtained based on recognition that chloride affinity of the second Lewis acid governs supercomplex formation. Aniline protonation was found to be the cause of incomplete reaction.