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Paper | Regular issue | Vol 96, No. 11, 2018, pp.1925-1939
Published online, 14th November, 2018
DOI: 10.3987/COM-18-13984
Utilization of Chlobenthiazone and Benazolin-ethyl as 4-Substituted 2(3H)-Benzothiazol-2-one Scaffolds

Masatoshi Kakuno, Shotaro Izawa, Taichi Takemoto, and Yoo Tanabe*

*Department of Chemistry, School of Scienece and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan

Abstract

N(3)-Substituted 4-aryl (or heteroaryl)-2(3H)-benzothiazol-2-ones were synthesized from readily accessible chlobenthiazone and benazolin-ethyl, a couple of N(3)-substituted 4-chloro-2(3H)-benzothiazol-2-one pesticides, utilizing Suzuki-Miyaura cross-coupling reactions (9 examples; 44–98% yield), although with less reactive stereocongested 4-chloro pendant substituent. In a similar fashion, N(3)-substituted 4-anilino (or BocNH)-2(3H)-benzothiazol-2-ones were synthesized from the 4-bromo analogues of the chlobenthiazone-utilizing Buchwald-Hartwig cross-coupling reactions (3 examples; 50–89% yield). In addition, a short synthesis of the key chloro-type quinone segment in natural mevashuntin with a unique 2(3H)-benzothiazol-2-one skeleton, was performed in three short steps with 61% overall yield. The obtained quinone segment functioned as a Diels-Alder reaction dienophile toward the Danishefsky-Kitahara diene as the model experiment. All schemes utilized a common cyclo-condensation using chlorocarbonylsulfenyl chloride for the construction of 4(ortho)-substituted 2(3H)-benzothiazol-2-one substrates.