Imposed hydrophobic interactions by NaCl: accountable attribute for the synthesis of spiro[acenaphthylene-1,5′-pyrrolo[1,2-c]thiazole] derivatives via 1,3-dipolar cycloaddition reaction in aqueous medium†
Abstract
We have described herein the significance of hydrophobicity for the synthesis of spiro[acenaphthylene-1,5′-pyrrolo[1,2-c]thiazole] derivatives through the 1,3-dipolar cycloaddition reaction of acenaphthenequinone, 1,3-thiazole-4-carboxylic acid and a Knoevenagel adduct in aqueous medium. The reaction was dramatically influenced by the presence of NaCl. In water alone, no reaction was observed due to the low magnitude of the hydrophobic effect. However, addition of NaCl augments the hydrophobic effect of water, which was actually found to impel the reaction by a notable magnitude and produced the desired product in high yield with excellent regio- and stereo selectivity. This imposed hydrophobic effect of NaCl is the deciding factor for making a new water-assisted strategy. To the best of our knowledge, this is the first report of a 1,3-dipolar cycloaddition reaction of azomethine ylides with olefin representatives in aqueous medium. This process is capable of generating four chiral centers comprising one spiro center with one C–N and two C–C bonds in a single reaction which enhances the biocidal profile or may reveal new medicinal properties. Exclusion of conventional organic solvents and toxic reagents, high atom-economy, mild reaction conditions, waste free synthesis and formation of water and carbon dioxide as the only by-products are additional advantages of the present methodology relevant to green chemistry.