The free radical chemistry of acyl tellurides: Mechanistic studies and synthetic applications
作者:Chen Chen、David Crich
DOI:10.1016/0040-4039(93)85002-e
日期:1993.3
Photolysis of acyl aryl tellurides in the presence of thiophenol results in the clean formation of aldehydes indicating homolytic cleavage of the acyl-Te bond and the involvement of acylradicals. Further cyclization reactions of unsaturated acyltellurides are reported together with some chemistry of the cyclization products.
Double cyclization of allyloxybenzoic acid chlorides mediated by samarium diiodide giving cyclopropanols
作者:Mitsuru Sasaki、Jacqueline Collin、Henri B. Kagan
DOI:10.1016/s0040-4039(00)82276-5
日期:——
Cyclopropanols were easily obtained by an unusual double cyclization of 2-allyloxybenzoic acid chlorides mediated by samariumdiiodide in THF. A tentative mechanism is discussed.
Generation and Cyclization of Acyl Radicals from Thiol Esters Under Nonreducing, Tin-Free Conditions
作者:David Crich、Xiaolin Hao
DOI:10.1021/jo970500j
日期:1997.8.1
The preparation of 2-(2-((tert-butyloxycarbonyl)amino)phenyl)ethyl mercaptan from 2-(2-amino-phenyl)ethanol is described. This thiol is condensed with a series of suitably unsaturated carboxylic acids to give a series of thiol esters. The Boc group is removed and the amine reacted with isoamyl nitrite to give a series of diazonium salts. Exposure to iodide in acetone solution then generates the aryl radical, which undergoes intramolecular homolytic substitution at sulfur with liberation of the acylradical. Following acyl radical cyclization, quenching by iodine and then elimination of HI leads to the isolation of alpha-methylene cycloalkanones in good yield.
Photoinduced Free Radical Chemistry of the Acyl Tellurides: Generation, Inter- and Intramolecular Trapping, and ESR Spectroscopic Identification of Acyl Radicals
作者:David Crich、Chen Chen、Jae-Taeg Hwang、Hongwei Yuan、Aristotle Papadatos、Robert I. Walter
DOI:10.1021/ja00099a011
日期:1994.10
Acyl tellurides are prepared in good to excellent yield by the reaction of sodium aryl tellurides with acyl chlorides, or mixed anhydrides, and are found to be moderately air-stable substances. In contrast to previous literature reports, acyl tellurides of aryl and vinyl carboxylic acids are found to be excellent sources of acyl radicals on photolysis with a simple white light source. The acyl radicals so generated may be trapped intermolecularly by dichalcogenides, or by TEMPO in excellent yield. Trapping by N-tert-butyl-alpha-phenyl nitrone produces a stable nitroxide radical which has been characterized by ESR spectroscopy. The very efficient trapping of acyl radicals by acyl tellurides themselves is demonstrated by a crossover experiment. Acyl tellurides are shown to participate in very efficient radical cyclization reactions onto alkenes with the formation of five-, six-, and eight-membered rings. The immediate products of the cyclizations onto alkenes are alpha-[(aryltelluro)methyl] ketones and the chemistry of these relatively unstable species is briefly described. Treatment with hydrogen peroxide affords alpha-methylene ketones in high yield. When elimination of the aryl telluro group is not possible the alpha-[(aryltelluro)methyl] ketones are stable species that may subsequently be employed in further radical chain reactions, for example with tributyltin hydride and methyl acrylate. Cyclization onto alkynes yields alpha-[(aryltelluro)methylene] ketones which are stable species and which take part in substitution reactions with higher order cuprates or with diphenyl diselenide.
Bachi, Mario D.; Denenmark, Daniella, Heterocycles, 1989, vol. 28, # 2, p. 583 - 588