Molybdenum(II)- and Tungsten(II)-Catalyzed Allylic Substitution
作者:Andrei V. Malkov、Ian R. Baxendale、Dalimil Dvořák、Darren J. Mansfield、Pavel Kočovský
DOI:10.1021/jo9821776
日期:1999.4.1
The molybdenum(II) complexes Mo(CO)(5)(OTf)(2) (7a), [Mo(CO)(4)Br(2)](2) (8a), their tungsten(II) congeners 7b and 8b, and bimetallic complex Mo(CO)(3)(MeCN)(2)(SnCl(3))Cl (9a) have been found to catalyze the C-C bond-forming allylic substitution with silyl enol ethers derived from beta-dicarbonyls (e.g., 16 + 30 --> 46) or from simple ketones (e.g., 16 + 32 --> 50), aldehydes, and esters as nucleophiles
Cobalt(II) chloride catalysed conversion of allylic alcohols to rearranged allylic amides
作者:Naresh K. Nayyar、M. Madhava Reddy、Javed Iqbal
DOI:10.1016/0040-4039(91)80456-g
日期:1991.11
Secondary and tertiary allylic alcohols can be converted to the corresponding allylically rearranged amides and acetates in presence of a catalytic quantity of cobalt(II) chloride and acetic anhydride in acetonitrile. Tertiary alcohols undergo complete rearrangement whereas the secondary ones yield a mixture of regioisomers.
Cobalt catalyzed regioselective allylation of 1,3-dicarbonyl compounds
作者:Golak C. Maikap、M. Madhava Reddy、Manoj Mukhopadhyay、Beena Bhatia、Javed Iqbal
DOI:10.1016/s0040-4020(01)85380-1
日期:1994.1
Catalytic amount of Cobalt(II) chloride in 1,2-dichloroethane promotes the allylation of 1,3-dicarbonyl compounds with allyl acetates in high yields. The allylation of pentane-2,4-dione is highly regioselective as compared with methylacetoacetate and ethyl 2-oxocyclopentanecarboxylate.
Cobalt(II)-Catalyzed Conversion of Allylic Alcohols/Acetates to Allylic Amides in the Presence of Nitriles
作者:Manoj Mukhopadhyay、M. Madhava Reddy、G. C. Maikap、Javed Iqbal
DOI:10.1021/jo00114a013
日期:1995.5
Various secondary allylic alcohols or their acetates and tertiary allylic alcohols can be converted to the corresponding transposed allylic amides in the presence of a catalytic quantity of cobalt(II) chloride and acetic anhydride in acetonitrile. Tertiary alcohols undergo complete rearrangement whereas secondary ones afford a mixture of regioisomers. Moderate yields of amides are also obtained by reacting acrylonitrile with secondary alcohols in 1,2-dichloroethane. The presence of acetic anhydride or acetic acid is crucial to the formation of amides as the absence of the former affords no amides and the allylic alcohols are mainly recovered as regioisomeric mixtures. The regioselectivity during amide formation can be enhanced by using cobalt complexes 14-16 in acetic acid medium. Some preliminary studies indicate that these reactions are proceeding via an pi-allyl complex or tight ion pair rather than a [3,3] sigmatropic rearrangement of acetamidate obtained in a Pinner reaction.
Kinetic resolution of racemic allylic acetates by asymmetric dihydroxylation (ADH) process: An indication of π-π interaction
作者:Braj B. Lohray、Vidya Bhushan
DOI:10.1016/s0040-4039(00)79261-6
日期:1993.6
Kinetic resolution of several racemic secondary allylic acetates have been examined using osmium tetroxide-cinchona alkaloid as chiral catalyst. The unexpected results have been rationalized with the help of model based on pi-pi interaction in the transition state apart from the matching and mismatching of the substrate and the catalyst.