Synthesis of<i>syn</i>and<i>anti</i>1,4-Diols by Copper-Catalyzed Boration of Allylic Epoxides
作者:Mariola Tortosa
DOI:10.1002/anie.201100613
日期:2011.4.18
Two sides of the same coin: Syn and anti 1,4‐diols have been synthesized through the regio‐ and diastereoselective CuI‐catalyzed boration of allylicepoxides (see scheme; pin=pinacolato, TES=triethylsilyl). In situ protection of the alcohol allows isolation of syn and anti 1,4‐silyloxyboronates. Monoprotected 1,4‐diols can be prepared by a one‐pot addition–protection–oxidation sequence.
Aryl- and alkenyl substituted oxiranes, when submitted to treatment with superbasic reagents, undergo a highly regio- and stereoselective rearrangement leading to cyclopropylmethanol derivatives. The process can also be applied to mono- and dihydroxy substituted substrates thus leading to polyhydroxylated cyclopropanes.
Highly enantioselective catalytic asymmetric epoxidation of α,β-unsaturatedcarboxylic acid imidazolides and simple amides was developed. In the presence of 5–10 mol% of lanthanide–BINOL complexes, the reaction proceeded smoothly with high substrate generality. In particular, in the cases of α,β-unsaturated amides, there was nearly perfect enantioselectivity (>99% ee). The corresponding epoxides were
Stereoselective Carbocyclization of Vinyloxiranes Catalyzed by Lewis Acids: Construction of the Musellarin Tricyclic Core
作者:Sehui Yang、Euijin Park、Jimin Kim
DOI:10.1002/bkcs.12236
日期:2021.4
Stereoselective carbocyclizations of vinyloxiranes were efficiently catalyzed by Lewis acids to provide cyclic homoallyl alcohols as single isomers. The choice of Lewis acid, B(C6F5)3 was crucial for the stereoselective transformation in the case of cis vinyloxiranes, whereas BF3∙OEt2 was proven to be an effective catalyst for trans substrates. The method was well implemented in the synthesis of seven‐membered
乙烯基氧杂环丁烷的立体选择性碳环化被路易斯酸有效地催化,以提供环状均烯丙基醇作为单一异构体。在顺式乙烯基环氧乙烷的情况下,路易斯酸B(C 6 F 5)3的选择对于立体选择性转化至关重要,而事实证明BF 3 ∙OEt 2是反式底物的有效催化剂。该方法在具有官能团耐受性的七元环和六元环的合成中得到了很好的实现。所得的效用反式-和顺高烯丙基醇被证明简明地建立musellarin A和E的三环核心