Effect of gem 2,2′-disubstitution and base in the formation of spiro- and ansa-1,3-propandioxy derivatives of cyclotriphosphazenes
摘要:
The gem-dialkyl effect has been investigated in the reactions of cyclotriphosphazene, N3P3Cl6 1, with various 2,2'-derivatives of 1,3-propandiol, CXY(CH2OH)(2), in either THF or DCM to form spiro (6-membered) and ansa (8-membered ring) derivatives. The reactions were made with a number of symmetrically-substituted (X = Y, methyl, ethyl, n-butyl and a malonate ester) and unsymmetrically-substituted (X not equal Y, methyl/H, phenyl/H, methyl/n-propyl, ethyl/n-butyl and Br/NO2) 1,3-propandiols. The products were analysed by H-1 and P-31 NMR spectroscopy and some of the spiro and ansa derivatives were also characterized by X-ray crystallography. Reactions of 1 with unsymmetrically-substituted 1,3-propandiols results in the formation of two structural isomers of ansa-substituted compounds, both isomers (endo and exo) have been structurally-characterized by X-ray crystallography for the ethyl/n-butyl derivative. It is found that the regioselectivity of the reaction is changed when the base is changed. The relative proportions of spiro and ansa compounds formed under different reaction conditions were quantified by P-31 NMR measurements of the reaction mixtures. The results were rationalised mainly in terms of the electronic effect of the substituents, whereas the steric effect has a secondary role in the formation of both spiro and ansa compounds. (C) 2010 Elsevier B.V. All rights reserved.
Electron transfer reduction of unactivated esters using SmI2–H2O
作者:Michal Szostak、Malcolm Spain、David J. Procter
DOI:10.1039/c1cc14014k
日期:——
The reduction of unactivated esters using samariumdiiodide is reported for the first time. The optimised protocol allows for the reduction of primary, secondary and tertiary alkyl esters in excellent yields and is competitive with reductions mediated by metal hydrides and alkali metals.
Selective pyrolysis of bifunctional compounds: gas-phase elimination of carbonate–ester functionalities
作者:Talal F. Al-Azemi、Hicham H. Dib、Nouria A. Al-Awadi、Osman M.E. El-Dusouqui
DOI:10.1016/j.tet.2008.01.002
日期:2008.4
Compounds containing both carbonate and ester functionalities were synthesized and then subjected to online-GC gas-phasepyrolysis. The carbonate groups were cleaved selectively in all elimination reactions. The end products of the reaction were found to be affected by the nature of the substrate. The presence of hydrogen and carbonyl substituents on the carbon β to the carbonate group resulted in
via the reaction of the four-membered ring thionation reagent [2,4-diferrocenyl-1,3,2,4-diathiadiphosphetane 2,4-disulfide (FcLR, a ferrocene analogue of Lawesson’s reagent)] and alkenyl/aryl-diols and I2 (or SOCl2) in the presence of triethylamine. Therefore, a series of five- to ten-membered heterocycles bearing an O-P(S)-O or an O-P(S)-S-S-P(S)-O linkage were synthesized. The synthesis features
3,4-Alkylenedioxy ring formation via double Mitsunobu reactions: an efficient route for the synthesis of 3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT) derivatives as monomers for electron-rich conducting polymers
作者:Kyukwan Zong、Luis Madrigal、L. ???Bert??? Groenendaal、John R. Reynolds
DOI:10.1039/b205907j
日期:2002.10.18
3,4-Alkylenedioxy ring functionalized thiophenes (XDOT’s) have been synthesized by double Mitsunobu reactions to yield precursors to monomers for conjugated and electrically conducting polymers, including the commercially important 3,4-ethylenedioxythiophene (EDOT).
A new and efficient synthetic route toward 3,4-alkylenedioxypyrrole (XDOP) derivatives via Mitsunobu chemistry
作者:Kyukwan Zong、L. ‘Bert’ Groenendaal、John R. Reynolds
DOI:10.1016/j.tetlet.2006.03.086
日期:2006.5
A new and high yielding synthetic route toward 3,4-alkylenedioxy-functionalized pyrroles has been achieved by performing tandem Mitsunobu reactions on diethyl 1-benzyl-3,4-dihydroxypyrrole-2,5-dicarboxylate using a variety of 1,2-alkanediols or 1,3-alkanediols.