Vilsmeier-Haack Reagents. Novel Electrophiles for the One-Step Formylation of<i>O</i>-Silylated Ethers to<i>O</i>-Formates
作者:Jean-Paul Lellouche、Vadim Kotlyar
DOI:10.1055/s-2004-815435
日期:——
Various O-silylated substrates were effectively converted in one-step to their corresponding O-formates using electrophilic racemic and homochiral Vilsmeier-Haack reagents. Reactivity trends of these transformations were examined that, specifically, emphasized their synthetic potential.
Sterically Hindered 2,4,6-Tri-<i>tert</i>-butylpyridinium Salts as Single Hydrogen Bond Donors for Highly Stereoselective Glycosylation Reactions of Glycals
作者:Titli Ghosh、Ananya Mukherji、Pavan K. Kancharla
DOI:10.1021/acs.orglett.9b00626
日期:2019.5.17
We demonstrate here that the strained and bulky protonated 2,4,6-tri-tert-butylpyridine salts serve as efficient catalysts for highlystereoselectiveglycosylations of various glycals. Moreover, the mechanism of action involves an interesting single hydrogen bond mediated protonation of glycals and not via the generally conceived Brønsted acid pathway. The counteranions also play a role in the outcome
C–H···Anion Interactions Assisted Addition of Water to Glycals by Sterically Hindered 2,4,6-Tri-<i>tert</i>-butylpyridinium Hydrochloride
作者:Ananya Mukherji、Pavan K. Kancharla
DOI:10.1021/acs.orglett.0c00348
日期:2020.3.20
conjugate acid of the bulky base 2,4,6-tri-tert-butylpyridine, under mild conditions, catalyzes the synthesis of silyl-protected 2-deoxy-hemiacetals and their dimerized products from glycals at varying concentrations of water. The criticality of the concentration of water in the reaction outcome is indicative of a unique mechanistic pathway for the bulky pyridine salt and not via the general Brønsted acid
TfO<sup>–</sup>···H–O–H Interaction-Assisted Generation of a Silicon Cation from Allylsilanes: Access to Phenylallyl Ferrier Glycosides from Glycals
作者:Rupa Bai Addanki、Suvendu Halder、Pavan K. Kancharla
DOI:10.1021/acs.orglett.2c00062
日期:2022.2.25
We demonstrate here that the strained and bulky protonated 2,4,6-tri-tert-butylpyridine (TTBPy) triflate salt serves as a mild and efficient organocatalyst for the diastereoselective C-Ferrier glycosylation of various glycals. The importance of the role of the 1/2 H2O molecule trapped in the catalyst has been disclosed. The mechanism of action involves unique anionic triflate and H2O hydrogen-bond
我们在此证明,紧张且庞大的质子化 2,4,6-三叔丁基吡啶 (TTBPy) 三氟甲磺酸盐可作为一种温和而有效的有机催化剂,用于各种糖基的非对映选择性C- Ferrier 糖基化。已经公开了捕获在催化剂中的1/2 H 2 O分子的作用的重要性。作用机制涉及独特的阴离子三氟甲磺酸酯和 H 2 O 氢键相互作用,有助于活化烯丙基硅烷,提供前所未有的非对映选择性苯基烯丙基 Ferrier 糖苷。
A New Procedure for Highly Regio‐ and Stereoselective Iodoacetoxylation of Protected Glycals and α‐1,2‐Cyclopropanated Sugars
作者:David W. Gammon、Henok H. Kinfe、Dirk E. De Vos、Pierre A. Jacobs、Bert F. Sels
DOI:10.1080/07328300701351524
日期:2007.5.31
less than 2 h at low temperatures to 2‐deoxy‐2‐iodoglycosyl acetates or novel 2‐deoxy‐2‐iodomethylglycosyl acetates using the simple, inexpensive reagent mixture of ammonium iodide, hydrogen peroxide, and acetic anhydride/aceticacid in acetonitrile. The protected glycals gave rise to 2‐deoxy‐2‐bromoglycosyl acetates when ammoniumbromide was used instead of the iodide, although longer reaction times