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A multicomponent two-step strategy for the synthesis of polysubstituted pyrrolo[3,2-c]pyridin-4-one derivatives has been described. The reactions can be readily performed by mixing inexpensive starting materials using two-step methods under mild conditions, and the products can be easily obtained from the mother liquid without any further treatment. Moreover, the solid acid catalyst can be circulated at least 6 times without obvious deactivation. Furthermore, a mechanism for the reaction process has been proposed. Overall the bond forming efficiency, the use of green solvent as the reaction medium, recyclability of the solid acid catalyst, easy work-up/purification, and a wide substrate scope make this method highly attractive to assemble heterocyclic scaffolds. [ABSTRACT FROM AUTHOR]

An efficient and green domino approach for the synthesis of 5,6,7,8-tetrahydropyrido[2,3-d]pyrimidin-4(3H)-one derivatives using a recoverable carbonaceous material as a catalyst has been established. The new domino reaction was conducted by reacting the readily available and inexpensive starting materials 2,6-diaminopyrimidin-4(3H)-one, nitroolefin and aldehyde in water. A total of 24 examples were examined, and showed a broad substrate scope and high yields. The carbonaceous material catalyst can be reused at least 5 times without obvious deactivation. The proposed mechanism has explained the reaction process and the resulting high regio- and diastereoselectivities. The present green strategy shows attractive characteristics such as using water as a green medium, using an inexpensive and recoverable solid acid catalyst, and having a simple work-up/purification, without generating any waste products or using any metal promoters. [ABSTRACT FROM AUTHOR]

A highly enantioselective group 5 metal amide catalyst system is reported for the hydroaminoalkylation of secondary amines to give chiral amines in good yields with excellent ee values (up to 93%) by loading of 5% precatalyst. [ABSTRACT FROM AUTHOR]

A new series of group 5 metal amides have been prepared from the reaction between V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) and chiral ligands, (R)-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (1H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (2H(2)), (R)-6,6'-dimethyl-2,2'-bis(mesitoylamino)-1,1'-biphenyl (3H(2)), (R)-2,2'-bis(mesitylenesulfonylamino)-6,6'-dimethyl-1,1'-biphenyl (4H(2)), (R)-2,2'-bis(diphenylthiophosphoramino)-1,1'-binaphthyl (5H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (6H(2)), (R)-2,2'-bis[(3,5-di-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (7H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-1,1'-binaphthyl (8H(2)), (S)-2-(mesitoylamino)-2'-(dimethylamino)-1,1'-binaphthyl (9H), and (R)-2-(mesitoylamino)-2'-(dimethylamino)-6,6'-dimethyl-1,1'-biphenyl (10H), which are derived from (R) or (S)-2,2'-diamino-1,1'-binaphthyl, and (R)-2,2'-diamino-6,6'-dimethyl-1,1'-biphenyl, respectively. Treatment of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 1 equiv of C(2)-symmetric amidate ligands 1H(2), 2H(2), 3H(2), 4H(2), and 5H(2), or Schiff base ligands 6H(2), 7H(2) and 8H(2) at room temperature gives, after recrystallization from a benzene, toluene or n-hexane solution, the vanadium amides (1)V(NMe(2))(2) (11), (2)V(NMe(2))(2) (14), (3)V(NMe(2))(2) (17), (5)V(NMe(2))(2) (22), (6)V(NMe(2))(2) (23) and (7)V(NMe(2))(2) (24), and niobium amides (1)Nb(NMe(2))(3) (12), (2)Nb(NMe(2))(3) (15), (3)Nb(NMe(2))(3) (18), (4)Nb(NMe(2))(3) (20) and [2-(3-Me(3)C-2-O-C(6)H(3)CHN)-2'-(N)-C(20)H(12)][2-(Me(2)N)(2)CH-6-CMe(3)-C(6)H(3)O]NbNMe(2)·C(7)H(8) (25·C(7)H(8)), and tantalum amides (1)Ta(NMe(2))(3) (13), (2)Ta(NMe(2))(3) (16), (3)Ta(NMe(2))(3) (19) and (4)Ta(NMe(2))(3) (21) respectively, in good yields. Reaction of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 2 equiv of C(1)-symmetric amidate ligands 9H or 10H at room temperature gives, after recrystallization from a toluene or n-hexane solution, the chiral bis-ligated vanadium amides (9)(2)V(NMe(2))(2)·3C(7)H(8) (27·3C(7)H(8)) and (10)V(NMe(2))(2) (28), and chiral bis-ligated metallaaziridine complexes (10)(2)M(NMe(2))(η(2)-CH(2)NMe) (M = Nb (29), Ta (30)) respectively, in good yields. The niobium and tantalum amidate complexes are stable in a toluene solution at or below 160 °C, while the vanadium amidate complexes degrade via diemthylamino group elimination at this temperature. For example, heating the complex (2)V(NMe(2))(2) (14) in toluene at 160 °C for four days leads to the isolation of the complex [(2)V](2)(μ-NMe(2))(2) (26) in 58% yield. These new complexes have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 12, 13, and 15-30 have further been confirmed by X-ray diffraction analyses. The vanadium amides are active chiral catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to good yields with good ee values (up to 80%), and the tantalum amides are outstanding chiral catalysts for the hydroaminoalkylation, giving chiral secondary amines in good yields with excellent ee values (up to 93%).

A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe(2))(4) (M = Ti, Zr) and chiral ligands, (R)-2,2'-bis(p-toluenesulfonylamino)-1,1'-binaphthyl (1H(2)), (R)-2,2'-bis(diphenylphosphinoylamino)-1,1'-binaphthyl (2H(2)), (R)-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (3H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(pyrrol-2-ylmethyleneamino)-1,1'-binaphthyl (4H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (5H(2)), and (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitylenesulfonylamino)-1,1'-binaphthyl (6H(2)), which are derived from (R)-2,2'-diamino-1,1'-binaphthyl. Reaction of M(NMe(2))(4) with 1 equiv of arylsulfonylamides 1H(2) and 6H(2), diphenylphosphoramide 2H(2), mesitoylamides 3H(2) and 5H(2), or Schiff base ligand 4H(2) at room temperature gives, after recrystallization from a benzene, toluene or n-hexane solution, the chiral titanium amides (1)Ti(NMe(2))(2).3C(6)H(6) (7.3C(6)H(6)), (4)Ti(NMe(2))(2) (11), (5)Ti(NMe(2))(2) (13) and (6)Ti(NMe(2))(2) (15), and zirconium amides (1)Zr(NMe(2))(2) (8), (2)Zr(NMe(2))(2) (9), (3)Zr(NMe(2))(2) (10), (4)Zr(NMe(2))(2) (12), (5)Zr(NMe(2))(2) (14) and (6)Zr(NMe(2))(2).C(7)H(8) (16.C(7)H(8)) respectively, in good yields. These amides are stable below 90 degrees C in toluene solution, but they degrade via ligand redistribution at a higher temperature. For example, treatment of (1)Zr(NMe(2))(2) (8) or (5)Zr(NMe(2))(2) (14) in refluxing toluene for three days leads to the isolation of the complexes (1)(2)Zr.C(7)H(8) (17.C(7)H(8)) and (5)(2)Zr.3C(7)H(8) (18.3C(7)H(8)) respectively, in moderate yields. These new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 7-9, 11-13, and 15-18 have further been confirmed by X-ray diffraction analyses. The titanium amide 13 and all the zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to excellent yields with moderate to excellent ee values (up to 93%). Theoretical studies reveal the interaction between the carbon chain of the substrate and the sterically demanding ligand groups plays a key role in the stereodirection of the enantioselection during the Zr=N bond approaches to the C=C bond.