(3+3)‐Annulation of 2‐Mercaptobenzimidazoles With α‐(Trifluoromethyl)Styrene Under Ultrasonic Irradiation

• Published in: European journal of organic chemistry Vol. 28; no. 4
• Main Authors: Sohail, Akbar, Ablajan, Keyume, Khan, Shahid Ali
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 24.01.2025; Wiley Subscription Services, Inc
• Subjects: (3+3)-Annulation; 2-Mercaptobenzimidazoles; Chemical reactions; Chemistry; Chemistry, Organic; Chromatography; Column chromatography; Functional groups; gem-Difluoro benzo[4,5]imidazo[2,1-b][1,3]thiazines; Mercaptobenzimidazole; Organic chemistry; Oxidizing agents; Physical Sciences; Recrystallization; Science & Technology; Styrenes; Substrate inhibition; Ultrasonic irradiation; α- (trifluoromethyl)styrene; 2-Mercaptobenzimidazoles; gem-Difluoro benzo[4,5]imidazo[2,1-b][1,3]thiazines; Ultrasonic irradiation; alpha- (trifluoromethyl)styrene; (3+3)-Annulation
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202401175

A rapid and facile sonochemical route for the [3+3] annulation of 2‐mercapto benzimidazoles with α‐(trifluoromethyl)styrene was reported for the synthesis of fluorinated benzo[4,5]imidazo[2,1‐b][1,3]thiazines. The reaction proceeds through the SN2/SNV pathway while the selective SN2 pathway is completely inhibited. The developed method is effective with a wide range of substrates, tolerating diverse functional groups. The pure products are obtained with high yield (up to 92 %) directly via recrystallization without column chromatography. Furthermore, applying sonochemical methodology reduces the reaction time and eliminates the need for expensive photocatalysts, ligands or oxidants. This protocol developed (3+3)‐annulation of 2‐mercaptobenzimidazoles with α‐(trifluoromethyl)styrene under ultrasonic irradiation. The cyclized product was formed through the Michael addition and intramolecular substitution reaction successively. The pure products were obtained with simple recrystallization.