carbodiimides in hydroxylic solvents containing hydrogenperoxide with mildly basic or acidic catalysts have been found to promote the epoxidation of olefins. A commercially available 30% aqueous solution of hydrogenperoxide serves as the oxidant for this process. The presumed reactive species is a peroxyisourea generated in situ by the addition of hydrogenperoxide to the carbodiimide.
Stereochemistry and mechanism of the Wittig reaction. Diasteromeric reaction intermediates and analysis of the reaction course
作者:Bruce E. Maryanoff、Allen B. Reitz、Martin S. Mutter、Robert R. Whittle、R. A. Olofson
DOI:10.1021/ja00284a034
日期:1986.11
respectively). The above-mentioned rate studies, entailing low-temperature ' 8 , I3C, and/or "P NMR spectroscopic measurements, indicate that the equilibration of cisto truns-oxaphosphetane arises from a larger rate of reversion of the cis-oxaphosphetane to ylide and aldehyde. Crossover experiments involving deprotonation of diastereomerically pure P-hydroxyphosphonium salts 7a and Sa (R = Ph), followed by the
The stereochemistry of the reactions between tris(2-methoxy-methoxyphenyl)phosphonioethanide (1f), -butanide (2f), and -phenyl-methanide (3f) and a variety of aldehydes was investigated. Ylides having a β-unbranched aliphatic sidechain, such as 2f, and saturated straight-chain aldehydes give olefins with unprecedented cis-selectivity (cis/trans â 200:1).
Synthesis of Cyclic Peroxides by Chemo- and Regioselective Peroxidation of Dienes with Co(II)/O<sub>2</sub>/Et<sub>3</sub>SiH
作者:Takahiro Tokuyasu、Shigeki Kunikawa、Kevin J. McCullough、Araki Masuyama、Masatomo Nojima
DOI:10.1021/jo048359j
日期:2005.1.1
Consistent with results from simple alkenes, the chemo- and regioselective peroxidation of dienes was also realized. Depending on the diene structure, the product included not only the expected acyclic unsaturated triethylsilyl peroxides but also 1,2-dioxolane and 1,2-dioxane derivatives via intramolecularcyclization of the unsaturated peroxy radical intermediates.
在两种烯烃与 Co(II)/O 2 /Et 3 SiH的混合物的竞争性过氧化反应中,发现烯烃底物的相对反应性受三个主要因素的影响:(1) 烯烃与 HCo(III) 络合物反应形成的中间碳中心自由基的相对稳定性,(2) C C 双键周围的空间效应,以及 (3) 与 C 相关的电子因素C 双键。与简单烯烃的结果一致,还实现了二烯的化学和区域选择性过氧化。根据二烯结构,产物不仅包括预期的无环不饱和三乙基甲硅烷基过氧化物,还包括 1,2-二氧戊环和 1,2-二氧六环衍生物,通过不饱和过氧自由基中间体的分子内环化。
Homoallylic substitution reactions of lithium dialkyl cuprates with cyclopropylcarbinyl halides: mechanistic considerations
作者:Robert T. Hrubiec、Michael B. Smith
DOI:10.1016/s0040-4020(01)91792-2
日期:1984.1
kanes, , react to give good yields of the homoallylic substitution product, . Less reactive organocuprates react with to give mixtures of and the direct substitution product, . These results are consistent with a copper(I) radical intermediate which undergoes facile rearrangement prior to reductive coupling.