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Paper | Regular issue | Vol 71, No. 10, 2007, pp.2219-2226
Published online, 20th July, 2007
DOI: 10.3987/COM-07-11124
Reaction of 3-Hydrazono-1,1,1-trifluoro-2-alkanones with Lawesson Reagent Accessing 6-Trifluoromethyl-3,6-dihydro-2H-[1,3,4]thiadiazines

Yasuhiro Kamitori,* Tomoko Sekiyama, and Etsuji Okada

*Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe 657-8501, Japan

Abstract

The reaction of 3-dimethylhydrazono-1,1,1-trifluoro-2-alkanones (1) with Lawesson reagent affording 6-trifluoromethyl-3,6-dihydro-2H-[1,3,4]thiadiazines (4) was elucidated in detail. The results indicate [1,5]sigmatropic hydrogen shift from N-methyl group to thiocarbonyl carbon on 3-dimethylhydrazono-1,1,1-trifluoro-2-alkanethiones (5) should readily proceed as a key step in this cyclization reaction. Similar [1,5]sigmatropic hydrogen shift on selenium analogues of 1 as well as that on imines derived from 1 are also studied on the basis of molecular orbital calculations.