Good cis selectivity is observed in the epoxidation of the cyclic allylic alcohols 2-cyclopentenol and 2-cyclohexenol due to a hydroxy-directing effect through hydrogen bonding; however, for 2-cycloheptenol and 2-cyclooctenol hydrogen bonding is ineffective and steric interactions cause a higher trans selectivity. The conformationally fixed cis- and trans-5-tert-butyl-2-cyclohexenols serve as suitable
作者:Richard C. Cambie、Diana M. Gash、Peter S. Rutledge、Paul D. Woodgate
DOI:10.1039/p19770001157
日期:——
Iodoacetoxylation of 3-t-butylcyclohexene with silver(I) acetate–iodine or thallium(I) acetate–iodine gives an ca. 3 : 1 mixture of t-2-iodo-t-3-t-butylcyclohexan-r-1-yl acetate and t-2-iodo-c-3-t-butylcyclohexan-r-1-yl acetate as the major products. The ratio is similar to that obtained for the major alcohols from reduction of the iodo-acetates with tri-n-butyltin hydride followed by lithium aluminium
Titanium-Catalyzed Heterogeneous Oxidations of Silanes, Chiral Allylic Alcohols, 3-Alkylcyclohexanes, and Thianthrene 5-Oxide: A Comparison of the Reactivities and Selectivities for the Large-Pore Zeolite Ti-β, the Mesoporous Ti-MCM-41, and the Layered Alumosilicate Ti-ITQ-2
A comparative study of silaneoxidation, olefin epoxidation, and thianthrene5-oxide sulfoxidation with the oxidants Ti-β/H2O2, Ti-MCM-41/t-BuOOH, and Ti-ITQ-2/t-BuOOH provides the catalytic reactivity order Ti-β>Ti-MCM-41>Ti-ITQ-2. The steric constraints of the narrow channels make the Ti-βzeolite the most selective. For the more open structures of the Ti-MCM-41 and Ti-ITQ-2 hosts, such steric constraints
用氧化剂Ti-β/ H 2 O 2,Ti-MCM-41 / t -BuOOH和Ti-ITQ-2 / t -BuOOH对硅烷氧化,烯烃环氧化和噻吨5氧化物硫氧化的比较研究提供了催化反应顺序为Ti-β> Ti-MCM-41> Ti-ITQ-2。狭窄通道的空间限制使Ti-β沸石具有最高的选择性。对于Ti-MCM-41和Ti-ITQ-2主体的更开放的结构,这种空间约束不太明显,因此,这些多相催化剂显示出较低的选择性。两者均通过类似于均相Ti(O i -Pr)4 / t的过渡结构激活t -BuOOH进行氧转移-BuOOH氧化剂。
A Simple and Efficient Oxidation Procedure for the Synthesis of Acid-Sensitive Epoxides
A mild and straightforward epoxidation protocol based on sodium perborate as primary oxidant and sodium dehydrocholate as organomediator under homogeneous conditions is described. In particular, geraniol, linalool, 3-carene, and α-pinene are quantitatively converted into the corresponding 6,7-epoxides and trans-epoxides, respectively. The bile acid salt is recovered from the reaction mixture and may be reused with unchanged efficiency and selectivity.
vic-Iodothiocyanates and iodoisothiocyanates. Part 3. Further preparations, and the formation of 2-alkoxy-2-thiazolines
作者:Richard C. Cambie、David Chambers、Peter S. Rutledge、Paul D. Woodgate、Sheila D. Woodgate
DOI:10.1039/p19810000033
日期:——
3-t-butylcyclohexene with iodine and potassium thiocyanate are examined. The action of iodine and thiocyanogen with (E)-hex-3-ene gives different results from those reported in the literature. Isomerizations of the vic-iodothiocyanates to vic-iodoisothiocyanates and formation of 2-alkoxy-2-thiazolines from the latter adducts are reported.