Microwave-Assisted Group-Transfer Cyclization of Organotellurium Compounds
摘要:
Primary- and secondary-alkyl aryl tellurides, prepared by arenetellurolate ring-opening of epoxides/O-allylation, were found to undergo rapid (3 - 10 min) group-transfer cyclization to afford tetrahydrofuran derivatives in 60-74% yield when heated in a microwave cavity at 250 degreesC in ethylene glycol or at 180 degreesC in water. To go to completion, similar transformations had previously required extended photolysis in refluxing benzene containing a substantial amount of hexabutylditin. The only drawback of the microwave-assisted process was the loss in diastereoselectivity which is a consequence of the higher reaction temperature. Substitution in the Te-aryl moiety of the secondary-alkyl aryl tellurides (4-OMe, 4-H, 4-CF3) did not affect the outcome of the group-transfer reaction in ethylene glycol. However, at lower temperature, using water as a solvent, the CF3 derivative failed to react. The microwave-assisted group-transfer cyclization was extended to benzylic but not to primary- and secondary-alkyl phenyl selenides.
Radical Carbonylation/Reductive Cyclization for the Construction of Tetrahydrofuran-3-ones and Pyrrolidin-3-ones
作者:Stefan Berlin、Cecilia Ericsson、Lars Engman
DOI:10.1021/jo030153f
日期:2003.10.1
beta-Hydroxyalkyl aryl chalcogenides obtained by regioselective ring-opening of epoxides with benzeneselenolate or -tellurolate were found to undergo efficient hetero-Michael addition when treated with ethyl propiolate. Subsequent carbonylation/reductive cyclization of the resulting vinylogous carbonates in the presence of AIBN/TTMSS and carbon monoxide (80 atm) afforded 2,5-disubstituted tetrahydrofuran-3-ones, predominantly as cis isomers (cis/trans = 4/1-9/1). Starting from a polymer-supported diaryl diselenide, the methodology was also successfully extended to solid-phase synthesis. Vinylogous carbamates prepared by hetero-Michael addition of aziridines to electron-deficient alkynes were regioselectively ring-opened with benzeneselenolate from the sterically least hindered side. Radical carbonylation/reductive cyclization of the resulting N-vinyl-beta-amino-alkyl phenyl selenides afforded 2,5-disubstituted pyrrolidin-3-ones, predominantly as cis isomers (cis/trans = 3/1-12/1).
10.3998/ark.5550190.p009.906
作者:Borges, Elton L.、Jacob, Raquel G.、Lenardão, Eder J.、Lima, David B.、Perin, Gelson、Silva, Márcio S.、Silva, Patrícia C.
DOI:10.3998/ark.5550190.p009.906
日期:——
Construction of Tetrahydrofuran-3-ones from Readily Available Organochalcogen Precursors via Radical Carbonylation/Reductive Cyclization
作者:Stefan Berlin、Cecilia Ericsson、Lars Engman
DOI:10.1021/ol016127q
日期:2002.1.1
[GRAPHICS]b-Hydroxyalkyl aryl chalcogenides, readily available by regioselective ring-opening of epoxides with nucleophilic benzeneselenolate or tellurolate, were O-alkylated by treatment with ethyl propiolate or (E)-1,2-bis(phenylsulfonyl)ethylene. Subsequent carbonylation/reductive cyclization in the presence of AIBN/TTMSS and carbon monoxide (80 atm) afforded tetrahydrofuran-3-ones in moderate to good yields.
NMR chiral discrimination of chalcogen containing secondary alcohols
作者:Naiade B.G. Marques、Raquel G. Jacob、Gelson Perin、Eder J. Lenardão、Diego Alves、Márcio S. Silva
DOI:10.1002/chir.23030
日期:2019.1
stable, nonhygroscopic, and readily available chiral derivatizing agent (CDA) for NMRchiral discrimination of chalcogen containing secondary alcohols. The chiralrecognition by CDA and chiralsolvatingagent (CSA) was assessed using 1H, 77Se‐1H}, and 125Te‐1H} NMRspectroscopy. A simple model for the assignment of the absolute configuration from NMR data is presented.
Microwave-Assisted Group-Transfer Cyclization of Organotellurium Compounds
作者:Cecilia Ericsson、Lars Engman
DOI:10.1021/jo040155f
日期:2004.7.1
Primary- and secondary-alkyl aryl tellurides, prepared by arenetellurolate ring-opening of epoxides/O-allylation, were found to undergo rapid (3 - 10 min) group-transfer cyclization to afford tetrahydrofuran derivatives in 60-74% yield when heated in a microwave cavity at 250 degreesC in ethylene glycol or at 180 degreesC in water. To go to completion, similar transformations had previously required extended photolysis in refluxing benzene containing a substantial amount of hexabutylditin. The only drawback of the microwave-assisted process was the loss in diastereoselectivity which is a consequence of the higher reaction temperature. Substitution in the Te-aryl moiety of the secondary-alkyl aryl tellurides (4-OMe, 4-H, 4-CF3) did not affect the outcome of the group-transfer reaction in ethylene glycol. However, at lower temperature, using water as a solvent, the CF3 derivative failed to react. The microwave-assisted group-transfer cyclization was extended to benzylic but not to primary- and secondary-alkyl phenyl selenides.