Toward Novel Antioxidants: Preparation of Dihydrotellurophenes and Selenophenes by Alkyltelluride-Mediated Tandem S<sub>RN</sub>1/S<sub>H</sub>i Reactions<sup>1</sup>
作者:Lars Engman、Melissa J. Laws、Jonas Malmström、Carl H. Schiesser、Lisa M. Zugaro
DOI:10.1021/jo9907235
日期:1999.9.1
distributions similar to those observed for reactions involving n-BuTeNa. Lithium or sodium phenyltellurolate returned only starting materials from these reaction mixtures. The 2-[2-(n-butyltelluro)-1-hydroxy-1-methyl]ethylphenyl radical (14) is estimated to cyclize with k(c) = 5 x 10(8) s(-)(1) at 25 degrees C. The tandem S(RN)1/S(H)i sequence has been applied to the preparation of the antioxidant analogues, 5-hydroxy-2
Homolytic substitution at selenium: A convenient synthesis of benzoselenophenes
作者:Carl H. Schiesser、Katarina Sutej
DOI:10.1016/s0040-4039(00)61211-x
日期:1992.8
tris(trimethylylsilyl)silane (TTMSS) in benzene at 80° (AIBN initiator) to give benzo-[b]selenophenes (3) in 80–86% yield. Interestingly, when the parent selenide (6: R1 = R2 = H) is reacted with tri-n-butyltin hydride under similar conditions, 3-hydroxydihydrobenzo[b]selenophene (2: R1 = R2 = H) is isolated as the only product of radical cyclization.
取代的2-苄基硒基-1-(2-碘苯基)乙醇(6)与苯中的三(三甲基硅烷基)硅烷(TTMSS)在80°(AIBN引发剂)下平稳反应,得到苯并[b]硒吩(3),在80-产率86%。有趣的是,当母体硒化物(6:R 1 = R 2 = H)在相似条件下与氢化三正丁基锡反应时,会分离出3-羟基二氢苯并[b]硒烯(2:R 1 = R 2 = H)作为自由基环化的唯一产物。
Free-radical homolytic substitution at selenium: an efficient method for the preparation of selenophenes
作者:Jennifer E. Lyons、Carl H. Schiesser、Katarina Sutej
DOI:10.1021/jo00073a021
日期:1993.10
Substituted and unsubstituted 1-(benzylseleno)-4-iodobut-3-en-2-ols 12 and 2-(benzylseleno)-1-(2-iodophenyl)ethanols 18 react smoothly with tris(trimethylsilyl)silane in benzene at 80-degrees-C (AIBN initiator) to afford selenophenes 16 and benzoselenophenes 21 in excellent yield. These reactions presumably involve intramolecular homolytic substitution by aryl and vinyl radicals 14 and 20 at the selenium atom with the expulsion of benzyl radical followed by facile dehydration to afford the aromatic selenophene ring system in each case. Competitive rate studies on the ring closure of the 2-[2-(benzylseleno)ethyl]phenyl radical 25 in the presence of tri-n-butyltin hydride to give 2,3-dihydrobenzo[b]selenophene (27) and 1-(benzylseleno)-2-phenylethane (28) provide a rate constant for ring closure (k(c)) of approximately 3 X 10(7) s-1 at 80-degrees-C. The determination of more accurate data is hampered by what we attribute to be the involvement of a slow, but competive nonradical process.
Preparation of benzocyclobutenols from o-halostyrene oxides
作者:Kasturi L. Dhawan、Barbara D. Gowland、Tony Durst
DOI:10.1021/jo01293a033
日期:1980.2
DHAWAN K. L.; GOWLAND B. D.; DURST T., J., ORG., CHEM., 1980, 45, NO 5, 922-924