Gold Catalyzed Redox Cyclization Of O-Nitroalkynes With H-Phosphorus Oxides

Indole ketone is a unique molecular skeleton,which widely exists in natural alkaloids and bioactive molecules.2-Phosphonyl indole-3-ones not only contains indolone skeleton but also introduces phosphorus,which has attracted great attention of researchers in the field of Medicine and Organic Chemistry.Therefore,it is very necessary to develop an economical synthetic method to construct 2-phosphonyl indole-3-ones.Phosphorus is one of the most abundant elements in the earth’s crust,and it plays an indispensable role in the life growth.Organic Phosphorus Compounds are widely used in agriculture,medicine,fluorescent material science and other fields because of their unique biological activities.Chiral BINOL phosphonic acids and chiral P(Ⅲ)ligands can be used as chiral catalysts for organic synthesis.In view of the wide application of Organic Phosphorus Compounds,they have been favored by many researchers in recent years,and many construction methods of Organic Phosphorus Compounds have been developed.However,transition metals catalyzed redox cyclization of o-nitroalkynes and H-phosphorus oxides for the construction of2-phosphonoindol-3-ones has not been reported.The research work of this paper is divided into two parts: one is the goldcatalyzed redox cycloisomerization/nucleophilic addition/reduction of onitroalkynes with H-phosphorus oxides for the synthesis of 2-phosphonoindol-3-ones;and the other is the asymmetric catalytic synthesis of2-phosphoryl indole-3-ones.In the first part of the paper,we developed an efficient gold(I)-catalyzed redox cycloisomerization/nucleophilic addition/reduction reaction of onitroalkynes with various H-phosphorus oxides.Through the intramolecular redox cycloisomerization of o-nitroalkynes and subsequent intermolecular nucleophilic addition/reduction with no external reductant,a variety of arylphosphoryl and alkylphosphoryl indolin-3-ones with high functionalgroup compatibility are obtained in moderate to good yields(27%-75% yield).Mechanistic studies suggest that phosphorus nucleophiles mediate the cleavage of the N-O bond as a reductant.In the second part of the paper,the asymmetric catalytic synthesis of 2-phosphonyl indole-3-ones was explored by screening different metal catalysts and chiral organic small molecular catalysts or chiral ligands,solvents and temperatures.The method for asymmetric synthesis of 2-phosphonyl indole-3-ones was determined.Under the catalysis of gold chloride and chiral BINOL phosphoric acid,chloroform was used as the reaction solvent,and the reaction was carried out at 20 ℃ for 24 h,the maximum enantiomer excess(ee value)was 36%.