The addition of benzoic acid as a co-catalyst facilitating cooperative Brønsted acid catalysis was found to be valuable for reactions involving phenols and higher substituted alcohols. Mechanistic investigations, including kinetic and 1H NMR binding studies in conjunction with density function theory calculations, are described that collectively support a Brønsted acid mode of catalysis.
Cupric sulfate pentahydrate (CuSO4·5H2O): a mild and efficient catalyst for tetrahydropyranylation/depyranylation of alcohols and phenols
作者:Abu T. Khan、Lokman H. Choudhury、Subrata Ghosh
DOI:10.1016/j.tetlet.2004.08.141
日期:2004.10
Various alcohols and phenols can be smoothly converted to the corresponding THP ethers using 20 mol % CuSO4·5H2O under mild reaction conditions at room temperature. Some of the major advantages of this procedure are nonaqueous work-up, very good yields, less expensive catalyst and compatibility with other protecting groups.
A Highly Efficient Synthetic Protocol for Tetrahydropyranylation/Depyranylation of Alcohols and Phenols
作者:Abu T. Khan、Subrata Ghosh、Lokman H. Choudhury
DOI:10.1002/ejoc.200500400
日期:2005.11
Bismuth(III) nitrate pentahydrate [Bi(NO3)3·5H2O] is found to be an effective catalyst for both tetrahydropyranylation and depyranylation of alcohols and phenols. Some of the major advantages of this protocol are: non-aqueous workup, good yields, the involvement of a less-expensive and nontoxic catalyst, and compatibility in the presence of a large number of other protecting groups. Notably, isopropylidene
Allyl tetrahydropyranyl ether: a versatile alcohol/thiol protecting reagent
作者:Brijesh Kumar、Mushtaq A. Aga、Debaraj Mukherjee、Swapandeep S. Chimni、Subhash C. Taneja
DOI:10.1016/j.tetlet.2009.09.026
日期:2009.11
Allyl tetrahydropyranylether (ATHPE) can be used as a versatile protecting reagent. In combination with NBS/I2, O-allyl group can easily be replaced by hydroxyls (including tertiary-OH) or thiols, in the molecules comprising other reactive functional groups such as halogen, nitro, acetonide and alkene under mild reaction conditions (near neutral pH and ambient temperature).
烯丙基四氢吡喃基醚(ATHPE)可用作通用保护剂。与NBS / I 2结合使用时,在温和的反应条件下(附近),在包含其他反应性官能团(例如卤素,硝基,丙酮化物和烯烃)的分子中,O-烯丙基可以轻松地被羟基(包括叔羟基)或硫醇取代。中性pH和环境温度)。
Generally Applicable Organocatalytic Tetrahydropyranylation of Hydroxy Functionalities with Very Low Catalyst Loading
作者:Peter Schreiner、Mike Kotke
DOI:10.1055/s-2007-965917
日期:2007.3
This paper presents the first acid-free, organocatalytic tetrahydropyran and 2-methoxypropene protection of alcohols, phenols, and other ROH derivatives utilizing privileged N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea and a polystyrene-bound analogue. The reactions are broadly applicably (also on preparative scale), in particular, to acid-sensitive substrates such as aldol products, hydroxy esters, acetals, silyl-protected alcohols, and cyanohydrins. The catalytic efficiency is truly remarkably with turnover numbers of 100,000 and turnover frequencies of up to 5700 h-1 at catalyst loadings down to 0.001 mol%. The computationally supported mechanistic interpretation emphasizes the hydrogen bond assisted heterolysis of the alcohol and concomitant preferential stabilization of the oxyanion hole in the transition state.