Lewis Acid Mediated “<i>endo-dig</i>” Hydroalkoxylation–Reduction on Internal Alkynols for the Stereoselective Synthesis of Cyclic Ethers and 1,4-Oxazepanes
作者:Santosh J. Gharpure、Dharmendra S. Vishwakarma、Santosh K. Nanda
DOI:10.1021/acs.orglett.7b03241
日期:2017.12.15
Lewisacidmediated 5/6/7-endo-dig hydroalkoxylation–reduction cascade on internal alkynols gave an expedient, stereoselective synthesis of cyclic ethers and 1,4-oxazepanes. The strategy has been extended to the first examples of hydroalkoxylation–alkyne Prins-type cyclization cascade of alkyne-tethered alkynols, giving access to oxa-bicyclic scaffolds. This method was used as the key step in the stereoselective
Effective synthesis of 2,5-disubstituted tetrahydrofurans from glycerol by catalytic alkylation of ketones
作者:Magnus Rueping、Vilas B. Phapale
DOI:10.1039/c1gc15764g
日期:——
The [IrCl(cod)]2 catalyzed α-alkylation of substituted acetophenones with solketal followed by reduction and iron mediated cyclization provides 2,5-disubstitutedtetrahydrofurans.
Organocatalytic synthesis of polysubstituted tetrahydrofurans from alkenes
作者:Alexis Theodorou、Christoforos G. Kokotos
DOI:10.1039/c6gc02580c
日期:——
A novel, organocatalytic and environmentally friendly protocol for the synthesis of polysubstituted tetrahydrofurans from trivial starting materials is described. Employing a 2,2,2-trifluoroacetophenone-mediated oxidation, which utilizes H2O2 as the green oxidant,...
O-Acyl derivatives of 3-hydroxy-gamma-butyrolactone are formed in up to 20% yield as by-products from 1-alkyl- and 1-phenyl-substituted 4-pentenols and tert-butyl hydroperoxide (TBHP) in vanadium-catalyzed synthesis of (tetrahydrofuran-2-yl)-methanols. The lactones are secondary products formed from (tetrahydrofuran-2-yl)-methanols via hydrogen atom abstraction in positions 4 and 5, as derived from experiments starting from deuterium-labeled alkenols. Stereocenters at tetrahydrofuran carbon 2 and the proximate hydroxyl carbon of the alkanol side chain retain configuration in the course of oxidative tetrahydrofuran conversion. In an atmosphere of nitrogen or argon, no gamma-butyrolactone formation occurs, pointing to dioxygen as terminal oxidant for the secondary oxidation. Adding cyclohexa-1,4-diene or gamma-terpinene to a solution of a 4-pentenol, TBHP, and a vanadium catalyst exposed to air inhibits formation of gamma-butyrolactones. A third approach to prevent gamma-butyrolactones from being formed in oxidative 4-pentenol cyclization uses cis-2,6-bis-(methanol)-piperidine instead of N-salicylidene-ortho-aminophenol as tridentate auxiliary for the vanadium catalyst. (C) 2014 Elsevier Ltd. All rights reserved.
LIPOXYGENASE-INHIBITING HYDROXAMIC ACID AND N-HYDROXYUREA DERIVATIVES