Catalytic reductive cyclization of substituted aromatic nitro compounds represents a valuable approach for the synthesis of N-containing heterocycles. Using gaseous CO as the reductant is possible to selectively transform the nitro group into much more reactive intermediates (such as nitroso compounds) that can further undergo inter or intra-molecular amination reactions.1 Nevertheless, CO is a highly toxic molecule whose handling requires the installation of expensive safety measures and high-pressure equipments. In order to overcome this issue, we developed a synthetic protocol in which formate esters (both alkyl and aryl) are employed as CO sources, thus avoiding the use of pressurized gas.2 In particular phenyl formate was found to be an excellent CO surrogate enabling the preparation of various substituted indoles by Pd-catalyzed reductive cyclization of ortho-nitrostyrenes with excellent selectivities. Notably, the transformation proceeds more efficiently than the corresponding reaction carried out under gaseous CO conditions. In addition, preliminary investigations devoted to the clarification of the reaction mechanism are presented.

Reductive cyclization of nitro compounds using CO surrogates: formate esters at work / D. Formenti, F. Ferretti, .F. Ragaini. ((Intervento presentato al 12. convegno Interdivisional Congress of Organometallic Chemistry of the Italian Chemical Society tenutosi a Genova nel 2016.

Reductive cyclization of nitro compounds using CO surrogates: formate esters at work

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

Abstract

Catalytic reductive cyclization of substituted aromatic nitro compounds represents a valuable approach for the synthesis of N-containing heterocycles. Using gaseous CO as the reductant is possible to selectively transform the nitro group into much more reactive intermediates (such as nitroso compounds) that can further undergo inter or intra-molecular amination reactions.1 Nevertheless, CO is a highly toxic molecule whose handling requires the installation of expensive safety measures and high-pressure equipments. In order to overcome this issue, we developed a synthetic protocol in which formate esters (both alkyl and aryl) are employed as CO sources, thus avoiding the use of pressurized gas.2 In particular phenyl formate was found to be an excellent CO surrogate enabling the preparation of various substituted indoles by Pd-catalyzed reductive cyclization of ortho-nitrostyrenes with excellent selectivities. Notably, the transformation proceeds more efficiently than the corresponding reaction carried out under gaseous CO conditions. In addition, preliminary investigations devoted to the clarification of the reaction mechanism are presented.
2016
Settore CHIM/03 - Chimica Generale e Inorganica
Reductive cyclization of nitro compounds using CO surrogates: formate esters at work / D. Formenti, F. Ferretti, .F. Ragaini. ((Intervento presentato al 12. convegno Interdivisional Congress of Organometallic Chemistry of the Italian Chemical Society tenutosi a Genova nel 2016.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/466409
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