Generation and reactions of thiocarbonyl S-(2,2,2-trifluoroethanides). Synthesis of trifluoromethylated 1,3-dithiolanes, thiiranes and alkenes

Abstract

The 'in situ' generated 1,1,1-trifluorodiazoethane reacts with thioketones as C=S dipolarophiles in a two-phase system (DCM/H 2 O) at room temperature to yield trifluoromethylated 2,5-dihydro-1,3,4thiadiazoles. Whereas stable crystalline products were obtained with cyclobutanethiones, the reaction with aromatic and heteroaromatic thioketones occured with spontaneous elimination of nitrogen. The formation of sterically crowded 4,4,5,5-tetrahetaryl-1,3-dithiolanes indicates that thiocarbonyl S-methanides are formed immediately and entered formal [3+2]-cycloaddition as diradical species with the starting thioketone. A protocol for the preparation of 3,3,3-trifluoropropene derivatives starting from corresponding thioketones and 1,1,1-trifluorodiazoethane is also presented.

Reaction of N,N‐Disubstituted Polyfluoroalkanethioamides with Diazomethane: Entry to New Thiirane Derivatives

“…Thiiranes 2a-e proved to be relatively unstable compounds and their purification by vacuum distillation or column chromatography was not efficient. The crude products were characterized by NMR ( 1 H, 13 C, 19 F) spectroscopy and GC-MS, and the obtained data are in good agreement with the structures 2a-e. In the 13 It is worth mentioning that the syntheses of 1-fluoroalkyl enamines containing dialkylamino group were performed previously using other methods.…”

“…Reaction monitoring using 19 F NMR spectroscopy revealed the consumption of the starting thioamides and the formation of derivatives 2a-e as the major products. Thiiranes 2a-e proved to be relatively unstable compounds and their purification by vacuum distillation or column chromatography was not efficient.…”

“…The composition of the isolated stereoisomers 8a and 8a′ is consistent with elemental analysis and FAB-MS data, which showed an intense peak of the deprotonated molecule [M -H]at m/z 393 in negative ionization mode for both compounds. The NMR ( 1 H, 13 C, 19 F) spectra of the two products are very similar with respect to chemical shifts and coupling constants. In the 19 F NMR spectra, the signals of trifluoromethyl groups of compounds 8a and 8a′ were found at -76.8 and -76.4 ppm, correspondingly.…”

“…[12][13][14][15] One of the general methods for the synthesis of thiiranes, which is based on the reaction of thiocarbonyl compounds with diazo compounds (Scheme 1), is applicable for the preparation of fluorinated thiirane derivatives too. This method gives access to the functionalized thiiranes and allows to use different fluorinated thiocarbonyl compounds (hexafluorothioacetone, [16,17] methyl trifluorodithioacetate [18] ) as well as diazo compounds [bis(trifluoromethyl)diazomethane, [11,17] 1,1,1-trifluorodiazoethane, [19] methyl 2-diazo-3,3,3-trifluoropropanoate [20] ].…”

Synthesis of Fluoro‐, Monofluoromethyl‐, Difluoromethyl‐, and Trifluoromethyl‐Substituted Three‐Membered Rings

“…To our knowledge, Heimgartner [94] et al. reported the unique synthesis of trifluoromethyl‐substituted episulfides during the last ten years.…”