Efficient one-pot synthesis of bis-benzothiazoles from dicarboxylic acids: A metal-free benzotriazole strategy

We report a green, metal-free, and efficient synthetic protocol for the preparation of bis-benzothiazoles via benzotriazole-mediated activation of dicarboxylic acids. This methodology employs N-acylbenzotriazole intermediates, which react with 2-aminothiophenol under mild conditions in acetic acid to afford the target bis-benzothiazoles in excellent yields. The process avoids the use of toxic reagents, metal catalysts, and harsh conditions, offering a sustainable alternative to conventional methods. Density functional theory (DFT) calculations provide mechanistic insights and thermodynamic profiles, highlighting the role of substituent effects and noncovalent interactions in product stability. The protocol demonstrates broad substrate scope, operational simplicity, and high atom economy, making it a valuable contribution to green heterocyclic synthesis. • A green, catalyst-free method for synthesizing bis-benzothiazoles using benzotriazole activation of dicarboxylic acids. • Mild reaction conditions in acetic acid produce excellent yields without using toxic reagents or metal catalysts. • A one-pot approach guarantees high atom economy and easy operation. • Broad substrate scope demonstrated across various dicarboxylic acids and linkers. • Benzotriazole intermediates facilitate regioselectivity and produce clean products. • DFT studies offer mechanistic insights into thermodynamic trends and substituent effects. • Sustainable method provides an eco-friendly alternative to traditional benzothiazole syntheses.