Itaru Nakamura

Palladium-catalyzed indolization of N-aroylbenzotriazoles with disubstituted alkynes.

The palladium-catalyzed denitrogenative indolization of N-aroylbenzotriazoles 1 and internal alkynes 2 produced the corresponding polysubstituted indoles 3 in good to high yields. For example, the reaction of 5,6-dimethyl-1-[4-(trifluoromethyl)benzoyl]benzotriazole (1j) with 6-dodecyne (2a), 4-octyne (2b), and diphenylacetylene (2f) in the presence of 10 mol % of Pd(PPh(3))(4) without solvent at 130 degrees C gave the corresponding indoles 3i, 3l, and 3p in 74, 71, and 41% yields, respectively. In the present reaction, the aroylbenzotriazole acts as a synthetic equivalent of a 2-haloanilide in Larocks indole synthesis.

Platinum-Catalyzed Dehydroalkoxylation-Cyclization Cascade via N-O Bond Cleavage

ortho-Alkynylphenylureas and -acetamides 1, with an alkoxy and aryl group on the nitrogen atom, were subjected to platinum-catalyzed cyclization reactions to afford the corresponding tetracyclic compounds 2, via N-O bond cleavage, in good to excellent yields. For example, N-methoxy-N-methyl-N-(2-(pent-1-ynyl)phenyl)-N-phenylurea (1a) was reacted for 12 h in the presence of PtI(4) (10 mol%) in 1,4-dioxane at 100 degrees C to afford 5-methyl-12-propylindolo[1,2-c]quinazolin-6(5H)-one (2a) in 93% yield, via an iminium-bound platinum carbenoid intermediate, followed by an aromatic C-H insertion.

Five-Bond Cleavage in Copper-Catalyzed Skeletal Rearrangement of O-Propargyl Arylaldoximes to β-Lactams

Copper-catalyzed skeletal rearrangement of O-propargyl arylaldoximes 1 produced the corresponding 4-arylidene-2-azetidinones 2 and their regioisomers 2 in good to excellent yields. For example, the reaction of benzaldehyde O-1,3-diphenylprop-2-ynyl oxime (1b) in the presence of 10 mol % CuBr in toluene at 100 degrees C for 24 h gave (E)-4-benzylidene-1,3-diphenylazetidin-2-one (2b) in 96% yield. (13)C labeling experiments suggest that the present reaction proceeds through bond cleavage of five different covalent bonds: C=N, N-O, C-O, C-C, and C[triple bond]C.