Selective Generation of Free Radicals from Epoxides Using a Transition-Metal Radical. A Powerful New Tool for Organic Synthesis
作者:T. V. RajanBabu、William A. Nugent
DOI:10.1021/ja00082a021
日期:1994.2
halogens provides a route to functionalized cyclopentanes and other useful products. The radical initially formed from an epoxide can also be trapped by H-atom donors such as 1,4- cyclohexadiene or tert-butyl thiol, resulting in an overall reduction of the epoxide. In the absence of a H-atom donor or an olefin, this radical is trapped by Ti(", resulting in a fl-oxido-Ti organometallic species which undergoes
Useful intermediates for intermolecular additions, reductions, and cyclizations are obtained with excellent regioselectivity via β-amido-substituted radicals catalytically generated from N-acyl aziridines. DFT calculations indicate that the ring opening is concerted rather than stepwise as previously postulated.
Catalytic Radical–Polar Crossover Reactions of Allylic Alcohols
作者:Eric E. Touney、Nicholas J. Foy、Sergey V. Pronin
DOI:10.1021/jacs.8b12075
日期:2018.12.12
Radical-polarcrossover hydrofunctionalizations of tertiary allylic alcohols are described. Depending on the structure of the catalyst, corresponding epoxides or semipinacol rearrangement products are selectively obtained in good yields. Experimental evidence points to the participation of alkylcobalt complexes as electrophilic intermediates.
Influence of strain on chemical reactivity. Relative reactivity of torsionally distorted double bonds in MCPBA epoxidations
作者:Kenneth J. Shea、Jang Seob Kim
DOI:10.1021/ja00034a042
日期:1992.4
The second-order reaction rata were measured for the MCPBA epoxidation in CH 2 Cl 2 for a series of cyclic olefins including bridgehead olefins and trans-cycloalkenes. As expected, strained bridgehead alkenes and trans-cycloalkenes showed faster reaction rates than nonstrained cis-cycloalkenes. The MM-2 steric energies of alkenes, alkanes, and their corresponding epoxides were calculated to evaluate
ZnCl2 (5 mol%) is an efficient catalyst for the thiolysis of 1,2-epoxides by thiophenol in water at pH 4.0. A variety of β-hydroxy phenylsulfides were obtained in short reaction times and excellent yields. Starting from cyclohexene oxide (1), two one-pot multi-step procedures in sole water (thiolysis/oxidation with H2O2) have been realized, for the chemoselective synthesis of the corresponding β-hydroxysulfoxides 19 or for the related β-hydroxysulfone 20.