DABCO-Catalyzed Green Synthesis of Thiazole and 1,3-Thiazine Derivatives Linked to Benzofuran

Abstract

An eco-friendly and simple procedure for the reaction of 2-(1-(benzofuran-2-yl)ethylidene)hydrazinecarbothioamide with arylidenemalononitriles and hydrazonoyl halides catalyzed by using sterically hindered organic base, 1,4-diazabicyclo[2.2.2]octane (DABCO) was described.This new protocol has the advantage of good yields and short reaction times.The structure of the newly synthesized compounds was elucidated via elemental analyses and spectral data.1,4-Diazabicyclo[2.2.2]octane (DABCO), a cage-like compound, is a small diazabicyclic molecule with weak alkalescence, medium-hindrance.It has been widely used in organic reactions and can serve as a weak base and ligand.DABCO is also used to adjust pH of the oxygen-sensitive resin to regulate the reaction rate in Flexplay time-limited DVDs.Antioxidants, such as DABCO are used to improve the lifetime of dyes.This makes DABCO useful in dye lasers and in mounting samples for fluorescence microscopy.DABCO is quite known to be an inexpensive, eco-friendly, high reactive, easy to handle and non-toxic base catalyst for various synthetic organic protocols, affording the corresponding products in excellent yields with high selectivity.][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] On the other hand, benzofuran derivatives are a class of fused ring heterocycles that are widely distributed in a large number of natural products and indeed occupy a characteristic site in the field of in medicinal chemistry. 19,202][23][24] Thiazole derivatives have been much more studied and synthesized, this is no doubt due to their wide spectra of biological behavior such as antimicrobial, antioxidant, 1450 HETEROCYCLES, Vol.92, No. 8, 2016 N R N Ar 5a-g O No. R Ar TEA DABCO Yield (%) Time (h) Yield (%) Time (h) 5a Me C6H5 67 4 75 1.