Tandem cyclization-cycloaddition reaction of rhodium carbenoids. Studies dealing with the geometric requirements of dipole formation
摘要:
The carbenoid intermediate derived by the treatment of several 1-diazobutanediones with rhodium(II) acetate undergoes ready transannular cyclization onto the neighboring keto group to give five-membered ring carbonyl ylides. The dipole derived from ethyl 4-diazo-2-methyl-3-oxobutyrate was found to undergo a rapid proton transfer, producing 5-ethoxy-4-methyl-3-(2H)-furanone. When the position adjacent to the diazo carbonyl group is blocked with two substituent groups, however, smooth 1,3-dipolar cycloaddition occurs. The observed regioselectivity can be nicely accommodated in terms of frontier molecular orbital (FMO) theory. A type II FMO interaction is involved since carbonyl ylides possess one of the smallest HOMO-LUMO energy gaps of common 1,3-dipoles. The rhodium(II)-catalyzed reaction of 1-diazo-6-phenyl-2,6-hexanedione afforded a mixture of products. In addition to the expected cycloadduct, a product derived from the bimolecular addition of the rhodium carbenoid to benzene was obtained. The formation of a mixture of products in this case suggests that entropic factors have sufficiently retarded the rate of intramolecular cyclization so as to allow the bimolecular reaction with benzene to occur. No observable cycloadduct was obtained from the diazohexanedione system, thereby indicating that the longer tether was sufficient to shut down dipole formation.
Cycloaddition of Carbonyl Ylides to Isatins: Synthesis of Novel Spiro Oxindoles
作者:Vijay Nair、K. C. Sheela、D. Sethumadhavan、S. Bindu、Nigam P. Rath、Günter K. Eigendorf
DOI:10.1055/s-2001-10764
日期:——
Facile dipolar cycloaddition reactions of isatins with carbonyl ylides, generated by Rh2(OAc)4 catalyzed reaction of α-diazo ketones yielding novel spiro oxindole derivatives are described.
Catalytic Enantioselective Tandem Carbonyl Ylide Formation/1,3-Dipolar Cycloaddition Reactions of α-Diazo Ketones with Aromatic Aldehydes using Dirhodium(II) Tetrakis[N-benzene-fused-phthaloyl-(S)-valinate]
example of the enantioselective intermolecular 1,3-dipolar cycloaddition of a chiral dirhodium(II) catalyst-associated carbonylylide with an aromatic aldehyde dipolarophile is described. The tandem carbonylylide formation/cycloadditionreactions of 1-diazo-5-aryl-2,5-pentanediones with aromatic aldehydes using dirhodium(II) tetrakis[N-benzene-fused-phthaloyl-(S)-valinate] as a catalyst provide exclusively
Cyclic carbonyl ylide formation from the rhodium (II) acetate catalyzed reaction of 1-diazoalkanediones
作者:Albert Padwa、Richard L. Chinn、Susan F. Hornbuckle、Lin Zhi
DOI:10.1016/s0040-4039(00)95185-2
日期:1989.1
Treatment of 1-diazoalkanediones with rhodium (II) acetate results in cyclization of the intermediate rhodium carbenoid to give a cyclic carbonyl ylide which readily undergoes bimolecular dipolar cycloaddition with various dipolarophiles.
Enantiocontrol in Tandem Carbonyl Ylide Formation and Intermolecular 1,3-Dipolar Cycloaddition of α-Diazo Ketones Mediated by Chiral Dirhodium(II) Carboxylate Catalyst