The Synthesis Of Esters And N-Heterocyclic Compounds Via Non-noble Metal-Catalyzed Inert C-C Bonds Cleavage

C-C bond is the most fundamental bond in organic compounds. C-C bond cleavage is a topic of significant importance in organic synthesis, which allows construction of new C-C bond from inert starting materials directly. Although significant advances have been made in the past decades, the development of inert C-C bond cleavage is a challenging problem in organic synthesis. To meet this challenge,noble metals are frequently employed. Copper and iron, two kinds of the common non-noble transition metals, are inexpensive and low-toxic, have been widely used in organic synthesis.By employing the non-noble metal copper or iron as catalyst, and the efficient formation of C-X(X= O, N, S) bonds via aerobic oxidation of C-H bonds and the cleavage of C-C bonds was achieved, which produces benzoates and N-heterocyclic compounds respectively. These reactions were traced by GC and GC-MS. The structures of product were determined by NMR analysis.(1) A copper-mediated coupling of benzonitriles with alcohols or phenols via aerobic cleavage of C-C bond has been developed, which gives benzoates by the use of molecular oxygen as the sole oxidant. Benzonitriles, bearing both electron-withdrawing groups and electron-donating groups, could react smoothly with alcohols to produce the corresponding benzoates under the optimal reaction conditions.It is noteworthy that easily oxidable phenols are also good substrates for this transformation. Moderate to excellent yields were observed(68-89%). Furthermore,the possible mechanism for this reaction is presented based on several controlled experiments.(2) An efficient synthesis of N-heterocycles via iron-catalyzed aerobic oxidation amination of carboxylic acid derivatives with o-substituted anilines has been developed. This transformation involves tandem the oxidation of C-H bond and the cleavage of C-C bond. Phenylacetic acids, bearing both electron-withdrawing groups and electron-donating groups could successfully react with o-substituted anilines to synthesize benzimidazoles, benzothiazoles, quinazolines, and quinazolinones under the optimal reaction conditions in moderate to excellent yields(60-92%). This tandem transformation represents a general protocol to construct N-heterocycles with broad substrate scope using iron as catalyst in combination with molecular oxygen or air asthe sole oxidant.