Visible light mediated cyclization of tertiary anilines with maleimides using nickel(II) oxide surface-modified titanium dioxide catalyst.

Surface-modified titanium dioxides by highly dispersed NiO particles have an extended absorption in the visible light region and a reduced hole-electron pair recombination than unmodified TiO2. They have now been successfully applied as highly active heterogeneous photocatalysts in the visible light mediated direct cyclization of tertiary anilines with maleimides to give tetrahydroquinoline products in moderate to high yields at ambient temperature. In contrast with unmodified titanium dioxide catalysts that are conventionally used in a stoichiometric amount in combination with UVA light, only a catalytic amount (1 mol %) of the surface-modified TiO2 catalyst is needed along with visible light to efficiently catalyze the reaction. Compared with transition-metal complexes such as Ru(bpy)3Cl2 or Ir(ppy)2(dtbbpy)PF6, advantages of these surface-modified titanium dioxides as photocatalyst include high catalytic activity, low cost, ease of recovering, and being able to be used for at least nine times without significant decay of catalytic activity.

{µ-6,6'-Dimeth-oxy-2,2'-[ethane-1,2-diyl-bis(nitrilo-methyl-idyne)]diphenolato-1κO,O,O,O:2κO,N,N',O}(methanol-1κO)(perchlorato-1κO)nickel(II)sodium.

The mol-ecule of the title compound, [NaNi(C(18)H(18)N(2)O(4))(ClO(4))(CH(3)OH)], is almost planar, the maximum deviation from the molecular plane being 5.3 (1) Å. The Ni(2+) ion is N(2)O(2) coordinated by the Schiff base ligand, leading to a slightly distorted square-planar environment. The Na atom is chelated by the four O atoms of the Schiff base ligand and is coordinated by the O atoms of a methanol ligand and a perchlorate anion. The perchlorate ion is disordered over two sites with occupancies 0.723 (12):0.277 (12).

{µ-6,6'-Dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato-1κO,O,O,O:2κO,N,N',O}(methanol-1κO)(perchlorato-1κO)copper(II)sodium(I).

The mol-ecule of the title compound, [CuNa(C(18)H(18)N(2)O(4))(ClO(4))(CH(3)OH)], is almost planar with mean deviation of 5.2 (8)°. The coordination environment of the Cu(II) ion is distorted square-planar and it is N(2)O(2)-chelated by the 6,6'-dimeth-oxy-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolate Schiff base ligand. The Na atom is chelated by the four O atoms of the Schiff base ligand, and coordinated by a methanol mol-ecule and a perchlorate anion. The six-coordinate Na atom adopts a distorted octa-hedral coordination geometry. The O atoms of the perchlorate anion are disordered over two sites with site-occupancy factors of 0.697 (5) and 0.303 (5). O-H⋯O hydrogen bonding occurs.

2-Meth-oxy-6-(6-methyl-1H-benzimidazol-2-yl)phenol.

The mol-ecule of the title compound, C(15)H(14)N(2)O(2) is almost planar, the dihedral angle between the 6-methyl-1H-benz-imidazole plane and the 2-methoxy-phenol plane being 6.9 (2)°. An intra-molecular O-H⋯N hydrogen bond is present. Adjacent mol-ecules are linked by N-H⋯O hydrogen bonds into a three-dimensional network structure. The benzoimidazole methyl group and its attached C atom are positionally disordered in a 0.724 (4):0.276 (4) ratio.

Au-catalyzed tandem cyclization/[1,2]-alkyl migration reaction of epoxy alkynes: synthesis of spiropyranones.

A novel gold-catalyzed tandem cyclization/[1,2]-alkyl migration process of epoxy alkynes to spiropyranones has been discovered. From this process, the construction of adjacent multiple stereocenters with a new quaternary carbon atom is achieved. The gold-catalyzed domino process is stereospecific with respect to the migrating carbon atom. A type of unusual C-C bond cleavage of epoxide systems has also been discovered, which can lead to the formation of two Z alkenes and a carbonyl functional group in one step with excellent stereoselectivity. Furthermore, this efficient domino process could be achieved in the presence of the simplest and least expensive gold catalyst [NaAuCl(4)].2H(2)O with a low catalyst loading.