Catalytic carbonylation processes represent a key synthetic tool for the preparation of bulk and fine chemicals. Furthermore, the CO molecule can be even employed as a stoichiometric reductant towards many functional groups. In particular, the transition-metal catalysed reductive cyclization of substituted aromatic nitro compounds allows for the synthesis of a large variety of N-containing heterocycles. However, from a laboratory-scale point of view, the use of pressurized CO requires the installation of expensive safety measures and high-pressure equipments. A solution to this problem is represented by the use of molecules capable of releasing an equivalent CO in situ. Among the various alternatives, formate esters (both alkyl and aryl) are the most promising one given their relative low cost, availability and functional group tolerance. Herein, we reported the use of formate esters as effective CO surrogates in the Pd-catalyzed reductive cyclization of substituted nitro compounds for the synthesis of heterocycles. Key for the success was the use of phenyl formate that, under optimal conditions, enable the synthesis of substituted indoles with excellent selectivities, while performing the reactions in an economical pressure tube without the need for autoclaves and/or a CO gas line. In addition, mechanistic investigations of the formate activation were performed in order to discriminate between a base-mediated and a metal-catalyzed process.

Pd-Catalyzed Synthesis of Heterocycles from Nitro Compounds using Liquid CO Sources / D. Formenti, F. Ferretti, F. Ragaini. ((Intervento presentato al 6. convegno EuChemS Congress tenutosi a Seville nel 2016.

Pd-Catalyzed Synthesis of Heterocycles from Nitro Compounds using Liquid CO Sources

D. Formenti;F. Ferretti;F. Ragaini
2016

Abstract

Catalytic carbonylation processes represent a key synthetic tool for the preparation of bulk and fine chemicals. Furthermore, the CO molecule can be even employed as a stoichiometric reductant towards many functional groups. In particular, the transition-metal catalysed reductive cyclization of substituted aromatic nitro compounds allows for the synthesis of a large variety of N-containing heterocycles. However, from a laboratory-scale point of view, the use of pressurized CO requires the installation of expensive safety measures and high-pressure equipments. A solution to this problem is represented by the use of molecules capable of releasing an equivalent CO in situ. Among the various alternatives, formate esters (both alkyl and aryl) are the most promising one given their relative low cost, availability and functional group tolerance. Herein, we reported the use of formate esters as effective CO surrogates in the Pd-catalyzed reductive cyclization of substituted nitro compounds for the synthesis of heterocycles. Key for the success was the use of phenyl formate that, under optimal conditions, enable the synthesis of substituted indoles with excellent selectivities, while performing the reactions in an economical pressure tube without the need for autoclaves and/or a CO gas line. In addition, mechanistic investigations of the formate activation were performed in order to discriminate between a base-mediated and a metal-catalyzed process.
2016
Settore CHIM/03 - Chimica Generale e Inorganica
Pd-Catalyzed Synthesis of Heterocycles from Nitro Compounds using Liquid CO Sources / D. Formenti, F. Ferretti, F. Ragaini. ((Intervento presentato al 6. convegno EuChemS Congress tenutosi a Seville nel 2016.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/466413
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