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Bhāvnagar, India

Dinda M.,AcSIR CSMCRI | Samanta S.,AcSIR CSMCRI | Eringathodi S.,AcSIR CSMCRI | Eringathodi S.,Indian Central Salt and Marine Chemicals Research Institute | And 2 more authors.
RSC Advances | Year: 2014

Solar photo-thermochemical C(sp3)-H bromination, conducted efficiently in a specially designed reactor, was reported recently. In the present study, the more complex formation of 4-bromo-2,5-substituted oxazoles from N-arylethylamides using this approach was achieved. The one-pot syntheses were carried out with N-bromosuccinimide-dichloroethane over 6 h (10.00 am to 4.00 pm) on sunny days. The isolated yields were in the range 42-82%. Benzylic bromination, followed by O-C bond formation through intramolecular nucleophilic substitution, and a second benzylic bromination followed by HBr elimination, gave the oxazole ring. A third bromination of the ring yielded the final product. The feasibility of synthesizing thiazole derivatives using a similar approach was also demonstrated. During the course of the reactions, succinimide and HBr were co-generated in the aqueous phase. Treatment with NaBrO3 and additional acid returned the reagent in 57% isolated yield upon chilling. The overall methodology was greener as a result. © 2014 The Royal Society of Chemistry.

Dinda M.,AcSIR CSMCRI | Chakraborty S.,AcSIR CSMCRI | Samanta S.,AcSIR CSMCRI | Bhatt C.,Indian Central Salt and Marine Chemicals Research Institute | And 5 more authors.
Environmental Science and Technology | Year: 2013

It has been reported by us recently that p-nitrobenzyl bromide (PNBBr) can be synthesized from p-nitrotoluene (PNT) in high isolated yield with respect to available bromine in 2:1 Br--BrO3 - employed as brominating reagent. The reaction was conducted in ethylene dichloride (EDC) and the substrate was taken in excess to suppress dibromo impurity formation. The product was "cold crystallized" from the reaction mass and the mother liquor was recycled in the subsequent batch thereby eliminating organic discharge. The present work attempts to further advance the synthesis of this commercially important molecule employed in protection-deprotection strategies. Herein its successful synthesis employing neat substrate and solar radiation as the sole energy source to drive this photothermochemical reaction is reported. Further, 100% pure PNBBr could be isolated from the solid reaction mass in 87% yield by leaching out the excess substrate through supercritical CO2 (Sc-CO2) extraction. The reaction was therefore accomplished cleanly in all respects and with low carbon footprint. © 2013 American Chemical Society.

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