• Clean Technology
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• v.20 no.2
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• pp.123-129
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• 2014

A green procedure is described for the preparation of a series of ionic liquids where two 3-methylimidazolium cations were bridged with ethylene glycol chain as linkers. Diethylene glycol-bis(3-methylimidazolium) ditosylate, triethylene glycolbis(3-methylimidazolium) ditosylate, and tetraethylene glycol-bis(3-methylimidazolium) ditosylate were heated with 3-methylimidazole under solvent-free condition to give the corresponding bis(3-methylimidazolium) ditosylate ionic liquids efficiently in a short time.

• Clean Technology
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• v.18 no.3
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• pp.325-328
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• 2012

The condensation reaction of 9,9'-bis(4-hydroxyphenyl)fluorene with epichlorohydrin to prepare 9,9'-bis[4(glycidyloxy) phenyl]fluorene (2), an important building block for fluorene-containing epoxy polymers, has been studied. The reaction is found to be quite sensitive to several experimental conditions such as reaction temperature and time, added amount of epichlorohydrin, the presence of catalysts and the use of co-solvent. Several conditions for obtaining the best yield in the reaction are: the reaction temperature is below 373 K and the reaction time is shorter than 1.5 h, and the ammonium salts act as a catalyst. Also, the use of ternary solvent (toluene, DMSO, water) has been proved to be crucial to maintain the reaction temperature and for an easy purification. Thus, the reaction proceeds in an environment-friendly manner where the use of reactants and the production of chemical wastes is minimized.

• Clean Technology
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• v.21 no.2
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• pp.102-107
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• 2015

Rhodamine dyes are widely used as fluorescent probes because of their excellent photophysical properties, such as high extinction coefficients, excellent quantum yields, great photostability, relatively long emission wavelengths. A great synthetic effort has been focused on developing efficient and practical procedures to prepare rhodamine derivatives, because for most applications the probe must be covalently linked to another (bio)molecule or surface. Sulforhodamine B is one of the most used rhodamine dyes for this purpose, because it carries two sulfoxy functions which can be easily utilized for binding with other molecules. Recently, we needed an expedient, practical synthesis of sulforhodamine derivatives. We found the existing procedure for obtaining those compounds unsatisfactory, particularly, with the cyclization process of the dihydroxytriarylmethane (1) to produce the corresponding xanthene derivative (2). We report here our findings, which represent modification of the existing literature procedure and provide access to the corresponding xanthene derivative (2) in a high yield. Use of methanol as a co-solvent was found quite effective to prohibit the water molecule produced during the cyclization reaction from retro-cyclizing back to the starting dihydroxytriarylmethane and the yield of the cyclization was increased (up to 84% from less than 20%). The reaction temperature was significantly lowered (80 vs. 135 ℃). Thus, the reaction proceeds in a higher yield and energy-saving manner where the use of reactants and the production of chemical wastes is minimized.