Abstract
Recently, the organic functionalization of polyoxometalates (POMs) has drawn increasing interest, and an easy and effective route to achieve organic derivatives is of great importance. Herein, the first reported synthesis of a tosyl ester derivative of the polyoxometalate (Bu4N)2[V6O13{(OCH2)3CCH2SO3C7H4}2]·2.5CH3CN (compound 1) was performed by using DMAP as an activating reagent and triethylamine as an HCl scavenger. The tosyl ester was transformed into an azide or halide group by using sodium azide or sodium bromide, respectively, as the nucleophilic agent. Two derivatives of POMs, (Bu4N)2[V6O13{(OCH2)3CCH2N3}2]·4CH3CN (compound 2) and (Bu4N)2[V6O13{(OCH2)3CCH2Br}2] (compound 3), were easily obtained. All the compounds were structurally and compositionally characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, NMR spectroscopy, ESI-MS, UV-Vis spectroscopy and TGA. This work provides a new route for the functional group transformation of organic derivatives of polyoxometalates.
Highlights
Tosylation of hydroxyl-functionalized substrates is an important transformation to activate hydroxyl groups, yielding substrates for further nucleophilic substitution in various fields of organic syntheses[1,2]
Excess organic substrates, longer reaction times and higher temperatures are required, but low yields are obtained in the stepwise functionalization of POMs compared with those of common functional group transformation reactions in organic chemistry, which are usually performed at room temperature within several hours[2,3]
Owing to the strong electron-withdrawing properties of POMs, tosylated derivatives of POMs are less likely than pure organic substrates to undergo nucleophilic substitutions
Summary
Tosylation of hydroxyl-functionalized substrates is an important transformation to activate hydroxyl groups, yielding substrates for further nucleophilic substitution in various fields of organic syntheses[1,2]. We sought to directly activate the hydroxyl groups of an organically derivatized POM through tosylation, to study the potential functional group transformations in POM chemistry. In this paper, beginning with the afforded pentaerythritol-derivatized hexavanadate containing two pendant hydroxyl groups as a starting material, p-toluene sulfonyl chloride as the sulfonyl source, DMAP as an activating reagent and triethylamine as the HCl scavenger, a tosyl ester derivative of a polyoxometalate, (Bu4N)2[V6O13{(OCH2)3CCH2SO3C7H4}2]·2.5CH3CN (compound 1), was synthesized with a good yield (as high as 60%). These compounds were characterized by single-crystal X-ray diffraction analysis
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