Arkivoc 2017, (ii), 138‐148
Perin, G et al
Scheme 3. Plausible mechanism for the formation of selenol esters 3. Once we had prepared a series of selenol esters derivative of glycerol, we evaluated the deprotection reaction of the ketal 3a, aiming to prepare the water‐soluble selenol ester 4a. Thus, stirring a solution of 3a in methanol at room temperature with a solid acid for 24 h afforded Se‐(2,3‐dihydroxypropyl)benzoselenoate 4a in 79% yield (Scheme 4).50 The solubility of the selenol ester 4a was determined as 8.6 g/mL at room temperature.
Scheme 4. Synthesis of Se‐(2,3‐dihydroxypropyl)benzoselenoate 4a. Conclusion We have demonstrated here the efficient synthesis of new glycerol‐based selenol esters by a green method using PEG‐400 as the solvent and Rongalite® as an inexpensive reducing agent for the cleavage of the Se‐Se bond. This method involves reactions of aromatic, aliphatic and heteroaromatic anhydrides 2 with racemic and enantiomerically pure bis‐(2,2‐dimethyl‐1,3‐dioxolanylmethyl)diselenide 1 at room temperature under basic medium. In this work, the products were prepared in moderate to good yields (55‐85%) after 20‐180 min of reaction. Additionally, it was demonstrated that the deprotection of the ketal protecting group in the selenol ester 3 produces water‐soluble selenol ester, which could be tested for its pharmacological activities. Experimental Section General. The reactions were monitored by thin layer chromatography (TLC) which was performed using Merck silica gel (60 F254), 0.25 mm thickness. For visualizing the spots, TLC plates were either exposed to UV light, or stained with iodine vapor, or 5% vanillin in 10% H2SO4 and heat. Column chromatography was performed using Merck Silica Gel (230‐400 mesh). Low‐resolution mass spectra (MS) were measured on a Shimadzu GC‐
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