5‐Chloro‐5‐trifluoromethyl‐3‐aryl‐4‐alkyl(aryl)‐isothiazolidines and their Dehydrochlorination Reactions

Abstract

N-Alkyl(aryl)-C-trifluoromethyl-C-chlorosulfinimides and styrenes react to give the 3ϩ2 cycloaddition products, 5chloro-5-trifluoromethyl-3-aryl-4-alkyl(aryl)-isothiazolidines 9a-h. The structure of the dehydrochlorination products derived from the compounds 9a-h is determined by the nature of the substituent near the nitrogen atom. The compounds having bulky tertiary-butyl group (9c,h) are transformed into the isothiazolines derivatives 10a,b, but compounds 9a,b,d-g form β-aminovinyl trifluoromethylthioketones 11a-f.The nature of the substituent near the nitrogen atom in the molecule 9 influences not only the thermal stability of the isothiazolidines but also their transformations during dehydrochlorination.Compounds 9c,h with a tertiary-butyl substituent near the nitrogen atom form isothiazolidines 10a,b upon heating with triethylamine in toluene. All the other isothiazolidine derivatives 9a,b,d-g are transformed into b-aminovinylthioketones 11a-f under the same conditions, meaning that hydrogen chloride elimination is accompanied by isothiazoline cycle opening.Examples of the isothiazoline cycle S-N bond rupture upon attack of nucleophilic reagents on the sulfur atom are known in the literature [12]. It may be assumed that the difference in the dehydrochlorination results for compounds 9 is caused by the shielding effect of the tertiary-butyl substituent, which prevents the attack on the sulfur atom in isothiazolines 10a,b by chloride ion. In contrast to this, the attack is possible in the isothiazolines 12, intermediately formed by dehydrochlorination of the compounds 9a,b,d-g. This attack results in the rupture of the sulfur-nitrogen bond and formation of thioketones 11a-f.Fluorine-containing thioketones 11c,e are red crystalline compounds and thioketones 11a,b,d,f are viscous red liquids which were purified by chromatography on silicagel. The first thioketones of this type were obtained as a result of β-aminovinylketones thionation [13].An apparently anomalous low-field chemical shift in the 1 H NMR spectra for the proton connected to nitrogen of compounds 11a-f (ϳ15 ppm) is noteworthy (see experimental part and [13]). The investigation of the structure of compound 11e by single-crystal X-ray diffraction allowed us to determine the reason of such a low-field δ NH value.

Comprehensive Experimental and Computational Study of η6-Arene Ruthenium(II) and Osmium(II) Complexes Supported by Sulfur Analogues of the β-Diketiminate Ligand

“…26 Subsequently, Walter et al reported increased yields employing Lawesson's reagent (LR) (Scheme 3)., 27,28 Since the initial report of the putative N-phenyl β-thioketoiminate by Duguary, only a handful of variants have been prepared and characterized, including α-trifluoromethyl-α′-phenyl and α,α′bis-phenyl substituted versions, but have not yet been employed as ligands. 30 In contrast, the synthesis of βselenoimines (β-aminoselenones) are currently unreported; hence, this work details the first known preparation and characterization of this selenium version of a β-diketiminate ligand, employing the commercially available Woollins' reagent (WR) as the selenium transfer reagent (Scheme 3). 44−46 A limited number of complexes featuring a β-thioimine are known, but include Cu(II), 31 Ti(IV), 32 Ni(II), 33 Pd(II), Pt(II), 34 Au(I), 35 and Cd(II), 36 where the metal center is bound by two coordinating thio-based ligands.…”