Convenient Preparation of Cyclic Acetals, Using Diols, TMS-Source, and a Catalytic Amount of TMSOTf
作者:Masaaki Kurihara、Wataru Hakamata
DOI:10.1021/jo020471z
日期:2003.5.1
amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf), carbonylcompounds are converted to acetals in good yields under mild conditions. This procedure, which was carried out without synthesizing the silylated diols, is a more convenient adaptation of Noyori's method. This acetalization applies to not only simple but also conjugated carbonylcompounds. Moreover, various TMS compounds, including
Diastereo-differentiating cyclopropanation of a chiral enol ether: a simple method for the preparation of optically pure cyclopropyl ethers
作者:Takashi Sugimura、Masato Yoshikawa、Tohru Futagawa、Akira Tai
DOI:10.1016/s0040-4020(01)87920-5
日期:1990.1
Enol ether of cyclohexanone carrying 2,4-pentanediol(PD) or 2,6- dimethyl-3,5-heptanediol(DMHD) as a chiral auxiliary was subjected to diastereo-differentiating cyclopropanation. The highest diastereomer excess(d.e.) of the product was found to be 95.2% in the case of PD and over 99.5% in the case of DMHD. The enol ethers prepared from various ketones and DMHD were also cyclopropanated in giving cyclopropyl
Stereospecificannulation of hydroxyvinylethers in the presence of triflic anhydride and tertiary amines and its syntheticapplication are described. Each 1-hydroxy-2-oxabicyclo[n.4.0]alkane, 2-oxabicyclo[n.4.0]alk-1(6)-ene and 2-oxabicyclo[n.4.0]alk-1(6+n)-ene is stereoselectively synthesized from the same hydroxyvinylether depending on the choice of the reaction conditions (temperature, solvent
描述了在三氟甲磺酸酐和叔胺存在下的羟基乙烯基醚的立体定向环氧化及其合成应用。每个1-羟基-2-氧杂双环[n.4.0]烷烃,2-氧杂双环[n.4.0] alk-1(6)-烯和2-氧杂双环[n.4.0] alk-1(6 + n)-烯根据反应条件(温度,溶剂和叔胺)的选择,由相同的羟基乙烯基醚立体选择性地合成。这些化合物导致多官能化的环状化合物和一些天然产物。我们提出,这种环化反应是通过纯S N 2样机理进行的。
Graphene-catalyzed transacetalization under acid-free conditions
作者:Medy C. Nongbe、Nicolas Oger、Tchirioua Ekou、Lynda Ekou、Benjamin K. Yao、Erwan Le Grognec、François-Xavier Felpin
DOI:10.1016/j.tetlet.2016.09.022
日期:2016.10
1,2- and 1,3-Diols are readily protected as cyclic acetals and ketals through a graphene-catalyzed transacetalization process. The methodology features an atom economic procedure since quasi-stoichiometric conditions have been developed. Unlike prior systems, the graphene-catalyzed transacetalization is performed under Brønsted and Lewis acid-free conditions and without solvent. Our method has been
Diastereo-differentiating intramolecular cyclopropanations of prochiral olefins and a diazo ester linked by optically active 2,4-pentanediol
作者:Atsushi Mori、Takashi Sugimura、Akira Tai
DOI:10.1016/s0957-4166(97)00040-2
日期:1997.3
Intramolecular cyclopropanation of 3, the substrate having a chiral auxiliary as a linking bridge between a diazo ester and cyclohexene, was found to give the cyclopropane 4 having over 99% diastereomeric excess (d.e.) in 91.5% yield. The reaction was also carried out at 138°C (p-xylene reflux) to give 4 of 88.2% d.e.