We report here various pathways by which six-membered N-heteroaromatic compounds react with benzynes that are generated by the HDDA reaction. The initially formed 1,3-zwitterionic species (a) can collapse intramolecularly to give novel 1 : 1 adducts of the heterocycle and benzyne; (b) can react with an externally added, electrophilic third-component to give functionalized heterocyclic products; or (c) can react with an external protic nucleophile to produce, following collapse of the ion pair resulting from protonation of the zwitterion, a variety of three-component assemblies. Mechanisms for formation of some of the 1 : 1 adducts are supported by DFT methods. The scope of the protic nucleophilic coupling was also expanded to a two-pot operation by using triflic acid as a protic "non-nucleophile", followed by the addition of a suitably reactive nucleophile.
Bibliographical noteFunding Information:
This work was supported by the National Institute of General Medical Sciences of the U.S. Department of Health and Human Services (R35 GM127097). Some of the NMR data were obtained with an instrument purchased with the support of the NIH Shared Instrumentation Grant program (S10OD011952). Computations were carried out using resources provided by the University of Minnesota Supercomputing Institute (MSI).
© 2019 The Royal Society of Chemistry.