77656-96-3Relevant articles and documents
Enabling CO Insertion into o-Nitrostyrenes beyond Reduction for Selective Access to Indolin-2-one and Dihydroquinolin-2-one Derivatives
Yang, Li,Shi, Lijun,Xing, Qi,Huang, Kuo-Wei,Xia, Chungu,Li, Fuwei
, p. 10340 - 10348 (2018/10/20)
The transition metal-catalyzed reductive cyclization of o-nitrostyrene in the presence of carbon monoxide (CO) has been developed to be a general synthetic route to an indole skeleton, wherein CO was used as a reductant to deoxidize nitroarene into nitrosoarene and/or nitrene with CO2 release, but the selective insertion of CO into the heterocyclic product with higher atom economy has not yet been realized. Herein, the Pd-catalyzed reduction of o-nitrostyrene by CO and its regioselective insertion were efficiently achieved to produce synthetically useful five- and six-membered benzo-fused lactams. Detailed investigations revealed that the chemoselectivity to indole or lactam was sensitive to the nature of the counteranions of Pd2+ precursors, whereas ligands significantly decided the carbonylative regioselectivity by different reaction pathways. Using PdCl2/PPh3/B(OH)3 (condition A), an olefin hydrocarboxylation was primarily initiated followed by partial reduction of the NO2 moiety and cyclization reaction to give N-hydroxyl indolin-2-one, which was further catalytically reduced by CO to afford the indolin-2-one as the final product with up to 95% yield. When the reaction was conducted under the Pd(TFA)2/BINAP/TsOH·H2O system (condition B), complete deoxygenation and carbonylation of the NO2 group occurred initially to yield the corresponding isocyanate followed by internal hydrocyclization to generate 3,4-dihydroquinolin-2-one with up to 98% yield. Importantly, the methodology could be efficiently applied in the synthesis of marketed drug Aripiprazole.
Experiments on the Chaperon effect in the nitration of aromatics
Strazzolini, Paolo,Giumanini, Angelo G.,Runcio, Antonio,Scuccato, Massimo
, p. 952 - 958 (2007/10/03)
A nitro group may be effectively delivered to the ortho position of alkylbenzenes, provided that a suitable chaperon function is located in α- position and a dilute of HNO3 in CH2Cl2 is used. The carbonyl function of an aldehyde or ketone is the best choice, but a carboxyl, alkoxycarbonyl, and amide groups all work well. The ether function showed a less pronounced ortho orientation effect, whereas the hydroxyl group was too prone to oxidation. Side reactions were minimal under the conditions employed. A para chaperon effect was seemingly at work in the CH2Cl2 nitration of benzenepropanenitrile. All the results were compared with the corresponding classical nitration in H2SO4.
