In the effort to identify new feedstocks for transition metal-catalyzed cross-couplings, we have been attracted to the use of alkyl amine derivatives. Amines are widely available, easily purified, and can be easily carried through multi-step sequences in protected form. Thus, they offer opportunities in late-stage functionalization and serving as simple building blocks. In particular, many benzylic amines are commercially available, or can be readily prepared via reduction of benzonitriles and other methods. We and others have previously shown that benzylic amines can be used in nickel-catalyzed cross-couplings with aryl and vinyl boronic acids via conversion to trimethylammonium triflates. However, preparation of ammonium triflate requires two steps from the primary amine, and is not compatible with the presence of other basic nitrogen atoms in the benzylic amine substrate, which limits the use of this chemistry to prepare heteroaryl-substituted products. Based on our recently developed strategy for C-N bond activation via the one-step conversion of alkyl amines into Katrizky pyridinium salts, we have developed cross-couplings of benzylic pyridinium salts and vinylboronic acids or esters. Via these benzylic pyridinium intermediates, benylic amines can be engaged in these cross-couplings via C-N bond functionalization. With the mild reaction conditions, heteroaryl substituents and a range of functional groups are well tolerated.

Vinylation of benzylic amines via C-N bond functionalization of benzylic pyridinium salts

2019 Fall National Meeting

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