Kumar D, Kuijken PF, van de Poel T, Neumann K, Galimberti DR. Revealing the Unique Role of Water in the Formation of Benzothiazoles: an Experimental and Computational Study.
Chemistry 2024;
30:e202302596. [PMID:
37812133 DOI:
10.1002/chem.202302596]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/05/2023] [Accepted: 10/07/2023] [Indexed: 10/10/2023]
Abstract
We present here a joint experimental and computational study on the formation of benzothiazoles. Our investigation reveals a green protocol for accessing benzothiazoles from acyl chlorides using either water alongside a reducing agent as the reaction medium or in combination with stoichiometric amounts of a weak acid, instead of the harsh conditions and catalysts previously reported. Specifically, we show that a protic solvent, particularly water, enables the formation of 2-substituted benzothiazoles from N-acyl 1,2-aminothiophenols already at room temperature, without the need for strong acids or metal catalysts. DFT Molecular Dynamics simulations coupled with advanced enhanced sampling techniques provide a clear understanding of the catalytic role of water. We demonstrate how bulk water - due to its extended network of hydrogen bonds and an efficient Grotthuss mechanism - provides a reaction path that strongly reduces the reaction barriers compared to aprotic environments, namely more than 80 kJ/mol for the first reaction step and 250 kJ/mol for the second. Finally, we discuss the influence of different aliphatic and aromatic substituents with varying electronic properties on chemical reactivity. Besides providing in-depth mechanistic insights, we believe that our findings pave the way for a greener route toward an important class of bioactive molecules.
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