Małgorzata Celeda

Synthesis of Imidazole Derivatives Using 2‐Unsubstituted 1H‐Imidazole 3‐Oxides

The reaction of 1,4,5-trisubstituted 1H-imidazole 3-oxides 1 with Ac2O in CH2Cl2 at 0 - 5° leads to the corresponding 1,3-dihydro-2H-imidazol-2-ones 4 in good yields. In refluxing Ac2O, the N-oxides 1 are transformed to N-acetylated 1,3-dihydro-2H-imidazol-2-ones 5. The proposed mechanisms for these reactions are analogous to those for N-oxides of 6-membered heterocycles (Scheme 2). A smooth synthesis of 1H-imidazole-2-carbonitriles 2 starting with 1 is achieved by treatment with trimethylsilanecarbonitrile (Me3SiCN) in CH2Cl2 at 0 - 5° (Scheme 3).

Reactions of Thioketones with a Fluorinated Thione S-Imide

N-(1-Adamantyl)hexafluorothioacetone S-imide (1) reacts readily with aromatic thioketones 4a−e to afford 1,4,2-dithiazolidines 5a−e as products of [3 + 2] dipolar cycloadditions. Unexpectedly, cycloadducts 5d and 5e, obtained from thioxanthione (4d) and 4,4′-(dimethoxy)thiobenzophenone (4e), respectively, are found to decompose at room temperature and could not be isolated as pure compounds. Unlike aromatic thiones, adamantanethione (4f) did not react with 1 at ambient temperature. However, reaction did occur upon heating in a sealed tube, and the new 1,4,2-dithiazolidine 9, bearing two adamantyl moieties, was isolated as the major product. The structure of 9 has been determined by X-ray diffraction analysis. The connectivity of the heterocyclic ring in this product indicates that the mechanism of its formation must proceed by a different route involving another in situ generated sulfur-centered 1,3-dipole. Retrocycloaddition of the primary adamantanethione cycloadduct 13 liberates hexafluorothioacetone, which is subsequently captured by S-imide 1 to give tetrakis(trifluoromethyl)-1,4,2-dithiazolidine 8 as a crystalline product. The structure of 8 has also been confirmed by X-ray diffraction analysis.

The unusual influence of hetaryl groups on the direct conversion of some secondary alcohols into thiols with Lawesson’s reagent: elucidation of the reaction mechanism

ABSTRACT A series of hetaryl-substituted methanols were used for direct conversion into the corresponding thiols by treatment with Lawesson’s reagent in boiling toluene. Unexpectedly, the respective sulfides were formed exclusively. In the case of chiral alcohols, the sulfides were obtained as 1:1-mixtures of meso- and dl-diastereoisomers. In contrast to hetaryl-substituted alcohols, the analogous protocol applied for benzhydryl alcohol led to a mixture of the expected secondary thiol and a bis(diphenylmethyl) trithiophosphonate. Finally, the analogous reactions with ferrocenyl(phenyl)methanol and diferrocenylmethanol, respectively, led to the corresponding thiols in good yield. GRAPHICAL ABSTRACT

An unexpected reaction of diethyl phosphite with electron-deficient dialkyl dicyanofumarates

GRAPHICAL ABSTRACT Abstract Diethyl phosphite reacts with both dimethyl dicyanofumarate and dicyanomaleate in boiling 1,2-dichloroethane to yield, after chromatographic workup, a 1:1-mixture of the corresponding meso- and dl-dicyanosuccinates. The analogous transformation was observed in the cases of diethyl and diisopropyl dicyanofumarates. A reaction pathway via initial formation of a P–C bond followed by its hydrolytic cleavage is proposed.

Synthesis of hetaryl-substituted 1,2,4-trithiolanes via a three-component reaction with dihetaryl thioketones, benzyl azide, and 2,2,4,4-tetramethyl-3-thioxocyclobutanone

ABSTRACT The three-component reactions with a hetaryl thioketone, 2,2,4,4-tetramethyl-3-thioxocyclobutanone, and excess benzyl azide performed at 60°C in the presence of LiClO4 lead to the formation of two types of 1,2,4-trithiolanes. As the major products, the non-symmetrical dihetaryl-substituted spiro-1,2,4-trithiolanes are formed. In addition, the symmetrical dispiro-1,2,4-trithiolane is identified. These products are formed in competitive [3+2] cycloadditions of the in-situ-generated thiocarbonyl S-sulfide with the thioketones used in the reaction. GRAPHICAL ABSTRACT

Reaction of 1-azabicyclo〔1.1.0〕butanes with 2,3-dicyanofumarates: interception of the intermediate zwitterions with methanol

The reaction of 3-phenyl-1-azabicyclo[1.1.0]butane (1c) with 2,3-dicyanofumarates ((E)-5) in dichloromethane at room temperature yields mixtures of cis- and trans-2,3-dicyano-4-phenyl-1-azabicyclo[2.1.1]hexane- 2,3-dicarboxylates (cis,trans-4). The proposed two-step reaction mechanism via a zwitterionic intermediate of type (6) is supported by trapping experiments with methanol: when the reactions of 1-azabicyclo[1.1.0]butanes (1) with dimethyl 2,3-dicyanofumarate ((E)-5a) are carried out in methanol, dimethyl (E)-2-(azetidin-1-yl)-3-cyanobut-2-enedioates (7) are formed as the only products.