Title:Three-Component Reaction of Benzothiazole, Acetylenic Esters, Phenoles; Synthesis of Dialkyl 2-benzo[d]thiazol Derivatives Under Grinding
Volume: 20
Issue: 4
Author(s): Farzaneh Fatemi , Hoorieh Djahaniani*Bita Mohtat
Affiliation:
- Department of Chemistry, East Tehran Branch, Islamic Azad University, PO Box 33955-163, Tehran,Iran
Keywords:
Three-component reaction, benzothiazole (BZT), 2-benzothiazole derivatives, environmentally benign procedure,
solvent-free grinding, biological interesting compounds.
Abstract: Aim and Objective: Due to biological activity of a significant number of compounds
containing benzothiazole ring system and in continuation of our interest in developing new
environmentally benign methods for the synthesis of heterocyclic compounds by MCRs in this study
we performed an efficient three-component from benzothiazole, acetylenic esters and hydroxyl
aromatics compounds to synthesize of 2- benzothiazole derivatives in high yield.
Materials and Methods: IR spectra were recorded using an FTIR apparatus. Melting points
measured on an Electrothermal 9100 apparatus. Spectra were obtained in solution of CDCl3 using
TMS as internal standard. Elemental analyses were carried out using a Heracus CHN–O– Rapid
analyzer. A mixture of benzothiazole, dimethyl acetylenedicarboxylate and phenol were placed in a
mortar. The mixture was ground with a mortar and pestle at room temperature for 12 min. After
completion of the reaction, as indicated by TLC (ethyl acetate: n-hexane, 1: 3), the solvent was
distilled off under reduced pressure and the residue was crystallized from diethyl ether.
Results: Treatment of benzothiazole and dialkyl acetylenedicarboxylates in presence of resorcinol
and β-naphthol led to products 4 (dialkyl (E)-2-(2-(2-hydroxyphenyl)benzo[d]thiazol-3(2H)-yl-3-
methylbut-2-enedioate), while we observed two isomer (Z) and (E) configurations (major and minor)
in nearly 70:30 ratio when the reaction was repeated in presence of 8-hydroxy quinolone and
DMAD. Also when we examined 2-nitro phenol, 4-nitrophenol, and 4-hydroxy quinoline, only one
product 5 was obtained. This indicates that the reaction proceeds efficiently with electron-releasing
substituted phenols.
Conclusion: The reaction between benzothiazole and dialkyl acetylenedicarboxylates in the presence
of some phenols without electron-withdraw substitution, presents a novel, one-pot, clean,
convenient, simple and inexpensive approach into the synthesis of 2-benzothiazole derivatives of
potential synthetic and pharmacologically interest. This procedure carries significant advantages
because of the minimization of labor, time, and cost.