Under microwave-activation polyethylene glycol bound 4-iodobenzoic acid could be readily reacted with various terminal alkynes in excellent yields and purity using polyethylene glycol (PEG) as a solid-liquid phase-transfer catalyst and polymer support; the cleavage could be dramatically accelerated under microwave activation.
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The 1H-NMR signal peaks of terminal OH groups on PEG 4000 (Mn=4000) are triplets at 4.56 ppm which are well separated from the 1H-NMR signal peaks of terminal CH2 groups on PEG supported 4-iodobenzoate at 4.38 ppm due to the electron-withdrawing effect of carboxyl groups linked to them. The loading capacity of PEG supported 4-iodobenzoate can be calculated on the integral of CH2 peaks, and that of OH peaks. Owing to the formation of PEG supported 4-iodobenzoate under DCC/DMAP being quantitative, the loading capacity of PEG supported 4-iodobenzoate is 0.5mmol/g.
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