A mild platinum-catalyzed dehydrogenation of R,β-sp3 C-H bonds adjacent to the nitrogen of tertiary amines was successfully established by Porf. LIANG Yongmin, visiting professor of the Lanzhou Institute of Chemical Physics, and his workers. And the in situ formed enamines initially serving as carbon-nucleophiles reacted with various nitroolefins, leading to the development of two one-pot protocols involving Michael addition-elimination and Michael addition-cyclization.

Michael addition is one of the most fundamental carbon-carbon bond forming reactions in organic chemistry, wherein enolates or stabilized carbanions are among the nucleophiles usually used for such a case. Enamines as enolate equivalents are employed extensively for the selective formation of C-C and C-N bonds in the Michael addition and Diels-Alder reaction, as well as a wide range of other reactions. In the synthetic chemistry of enamines, the condensation between an amine and a carbonyl compound constitutes the classical method for the formation of enamines in which acidic, basic, and/or azeotropic conditions are usually required. As an alternative synthetic route, enamines can also be generated from dehydrogenation of tertiary amines mediated by transition metals. However, these methods are frequently restricted to relatively harsh reaction conditions. Thus, a mild method for the straightforward synthesis of enamines is still of high demand in modern organic synthesis.

Recently, the activation of the hydrogen located at the α-position of the nitrogen atom represents a useful method for the construction of complex molecules. Of them, the cross-dehydrogenative coupling (CDC) constitutes one of such important synthetic transformations involving R C-H oxidative activation of tertiary amines.

This platinum-catalyzed reaction provided an effective access to structurally divergent heterocyclic compounds. Additionally, the present reaction can tolerate a large number of substrates, including aromatic and aliphatic nitroolefins as Michael acceptors as well as various functionalized (E)-nitrovinylphenols as Michael acceptors/donors with significant structural variation.

The detailed report of the work was published in J. Org. Chem. (J. Org. Chem. 2010, 75, 2893–2902). 

Abstract of the paper published in J. Org. Chem.