Tellurium in Organic Synthesis. Preparation of Z-Vinylic Cuprates from Z-Vinylic Tellurides and Their Reaction with Enones and Epoxides
摘要:
Z-Vinylic tellurides, obtained with 100% stereoselectivity by the hydrotelluration of acetylenes, are easily transformed into Z-vinylic higher order cyanocuprates by reaction with preformed Me(2)Cu(CN)Li-2, n-Bu(2)Cu(CN)Li-2, or n-Bu(2-Th)Cu(CN)Li-2, with total retention of the double-bond configuration. The resulting vinylic higher order cyanocuprates react with unhindered enones to give the corresponding 1,4-addition products in good yields. Reaction of the vinylic higher order cyanocuprates with monosubstituted epoxides at 0 degrees C gives the homoallylic alcohols resulting from the attack to the less-substituted carbon atom, while the disubstituted epoxides failed to react. Allylic epoxides react at -78 degrees C with the vinylic higher order cyanocuprates to give mixtures of 1,2- and 1,4-opening products, the 1,4-product predominating. In all cases the double-bond configuration of the original vinylic telluride was preserved. The vinylic cuprates derived from simple vinylic tellurides and conjugated 1-telluroenynes react with epoxides at 0 degrees C, while vinylic cuprates derived from conjugated 1-tellurodienes required the addition of 1 equiv of BF3 . Et(2)O to give the homoallylic alcohols on reaction with epoxides. The opening of optically pure epoxides through tellurium/copper transmetalation is stereospecific, giving one single stereoisomer of the corresponding homoallylic alcohol.
Synthesis and antidepressant-like activity of selenophenes obtained viairon(iii)–PhSeSePh-mediated cyclization of Z-selenoenynes
作者:Bibiana M. Gai、André L. Stein、Juliano A. Roehrs、Filipe N. Bilheri、Cristina W. Nogueira、Gilson Zeni
DOI:10.1039/c1ob06548c
日期:——
We present here the synthesis and antidepressant-like action of a series of 2,5-disubstituted-3-(organoseleno)-selenophenes prepared by a novel synthetic route, the FeCl3âdiorganyl dichalcogenide-mediated intramolecular cyclization of (Z)-chalcogenoenynes. The cyclized products were obtained in good yields. The results showed that 2c, 2d, 2e and 2o, evaluated in the mouse forced-swimming test, elicited an antidepressant-like activity. The studies clearly show that the phenyl group at the 2-position and an organoselenium group at the 3-position of the selenophene ring are essential for the antidepressant-like activity of selenophenes. A close inspection of the results also revealed that the fluorophenyl portion in the organoselenium group is fundamental for the antidepressant-like action of this class of organochalcogens.
Influence of the gegenion in the transmetalation reaction of vinylic tellurides with higher order cyanocuprates
作者:André Chieffi、João V. Comasseto
DOI:10.1016/s0040-4039(00)73112-1
日期:1994.6
Dilithium cyanocuprates R2LCu(CN)Li2 (L=2-Th, Me) react with vinylictellurides of Z configuration, RCHCHTeR1 to give higherordervinyliccyanocuprates, [(RCHCH)LCu(CN)Li2]. By changing the gegenion from lithium to magnesium [R2LCu(CN)LiMgBr or R2LCu(CN)(MgBr)2] the reaction gives cross - coupling products of Z configuration, RCHCHR2 in good yields.
An intramolecular [4+2] cycloaddition of 1-(9-anthrylchlorophosphino)-1,4-diphenylbut-1-en-3-yne produced the 1-(chlorophosphino)-1,4-diphenyl-1,3-butadiene derivative incorporated with a dibenzoba...
We present here our results of the electrophilic cyclization reaction of (Z)-chalcogenoenynes using butyltellurium tribromide as an electrophilic source. The cyclization reaction proceeded cleanly under mild reaction conditions and 3-(butyltellanyl)chalcogenophenes were formed in moderate to excellent yields. Subsequent, using these heterocycles as substrate to palladium-catalyzed cross-coupling reactions a new carbon-carbon bond was formed in good yields.
Synthesis and Photophysical Properties of Dibenzobarrelene-Incorporated 1,4-Diphenyl-1,3-pentadienes and a 5-Sila Derivative Having High Fluorescence Efficiency
dibenzobarrelene 1,3‐pentadienes and a sila derivativehave been synthesized. They all show similar luminescence properties in CH2Cl2, whereas in the solid state, differences in the luminescence of the CH2 and SiMe2 derivatives and that of CHOH arise due to intermolecular hydrogen bonding in the latter. The fluorescence intensity of the SiMe2 derivative was markedly reduced by desilylation.