A Multipathway Coupled Domino Strategy: Metal-free Oxidative Cyclization for One-Pot Synthesis of 2-Acylbenzothiazoles from Multiform Substrates

Abstract

A multipathway coupled domino strategy has been developed for the efficient synthesis of 2-acylbenzothiazoles from multiform substrates arylethenes, arylacetylenes, 2-hydroxy-aromatic ketones, and carbinols via four distinct pathways. Through a logical coupled oxidation/heterocyclization domino process, a variety of 2-acylbenzothiazoles were synthesized free of metal in one pot.

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“…They converted these substrates into aryl substituted glyoxal in situ, which condensed with various 2-aminothiophenol in one-pot metal-free reaction (Scheme 24) 51 . This synthetic approach embodied four specific reaction pathways.…”

Recent Advances in Transition‐Metal‐Free Oxygenation of Alkene C=C Double Bonds for Carbonyl Generation

“…For example, Wu and co‐workers realized the direct synthesis of 2‐aroyl benzothiazoles 61 starting from aryl alkenes 28 and o ‐aminothiophenol 60 in the presence of I 2 /IBX. In the formation of the target product, the I 2 /IBX‐promoted iodoxygenation of the C=C double‐bond to form intermediate type 55 was one of the key transformations, which allowed the further oxidation to give α‐oxoaldehyde 62 and enabled the final production of 61 (Scheme ) …”

TsNBr2 Mediated Synthesis of 2‐Acylbenzothiazoles and Quinoxalines from Aryl Methyl Ketones under Metal Free Condition

“…Mali et al ., developed a copper‐II mediated protocol for the synthesis of 2‐acylbenzothiazole in presence of oxygen under reflux condition using ethanol as a solvent . Transformation of 2‐aminobenzenethiol to corresponding 2‐acylbenzothiazole can also be achieved via a cascade pathway using arylethenes, arylacetylenes, 2‐hydroxy‐aryl ketones, and 1‐arylethanol in presence of I 2 and IBX in DMSO . Alternatively, 2‐acylbenzothiazole can be synthesized via oxidative acylation of corresponding unsubstituted benzothiazole using aryl methyl ketones in presence of a catalyst such as FeCl 3 .6H 2 O, FeCl 3 .6H 2 O with K 2 S 2 O 8, CuI with HBF 4, or iodine as an oxidant at high temperature (≥100 °C) .…”