Carbodiimide insertion into sulfonimides: one-step route to azepine derivatives via a two-atom saccharin ring expansion

Copper(II) Prevents the Saccarine-Dialkylcyanamide Coupling by Forming Mononuclear (Saccharinate)(Dialkylcyanamide)copper(II) Complexes

The reaction in the system CuII/sacNa(H)/NCNR2 (sacNa(H) = sodium saccharinate (saccharin); R = Me, Et) results in the formation of the complexes [Cu(sac)2(NCNR2)(H2O)2] (R = Me 1, Et 2) instead of the expected products derived from the saccharin–cyanamide coupling. Complexes 1, 2, and hydrate 1·2H2O were characterized by IR, AAS (Cu%), TGA, and also by single-crystal X-ray diffraction for 1 and 1·2H2O. An integrated computational study of model structure 1 in the gas phase demonstrates that the Cu–Ncyanamide and Cu–Nsac coordination bonds exhibited a single bond character, polarized toward the N atom and almost purely electrostatic, with the calculated vertical total energies for the Cu–Ncyanamide and Cu–Nsac of 43.6 and 156.4 kcal/mol, respectively. These data confirmed that the copper(II) completely blocks the nucleophilic centers of ligands via coordination, thus preventing the saccharin–cyanamide coupling.

Novel Convenient Approach to 6-, 7-, and 8-Numbered Nitrogen Heterocycles Incorporating Endocyclic Sulfonamide Fragment

A new effective method for the construction of nitrogen heterocycles incorporating endocyclic pharmacophore sulfonamide fragment, based on the use of easy accessible N-(chlorosulfonyl)imidoyl chloride, CCl₃C(Cl)=NSO₂Cl (1), has been developed. Thus, a reaction of 1 as bielectrophilic 1,3-C–N–S reagent with benzylamines that act as 1,4-N–C–C-C binucleophiles, affords respective 1,2,4-benzothiadiazepine-1,1-dioxides. On the other hand, 1 reacts with alkenyl amines with the formation of respective N-alkenyl amidines undergoing Lewis acids initiated intramolecular cyclization to afford derivatives of 1,2,4-thiadiazines and 1,2,4-thiadiazocines bearing a halomethyl group able for further functionalization. The first examples of electrophilic heterocyclization of the chlorosulfonyl group onto an alkenyl or alkynyl group have been revealed.

Catalytic Room-Temperature C-N Coupling of Amides and Isocyanates by Using Mechanochemistry

A mechanochemical route is developed for room-temperature and solvent-free derivatization of different types of amides into carbamoyl isatins (up to 96 % conversion or yield), benzamides (up to 81 % yield), and imides (up to 92 % yield). In solution, this copper-catalyzed coupling either does not take place or requires high temperatures at which it may also be competing with alternative thermal reactivity, highlighting the beneficial role of mechanochemistry for this reaction. Such behavior resembles the previously investigated coupling with sulfonamide substrates, suggesting that this type of C-N coupling is an example of a mechanochemically favored reaction, for which mechanochemistry appears to be a favored environment over solution.

Saccharin guanidination via facile three-component “two saccharins-one dialkylcyanamide” integration

Novel three-component “two saccharins-one dialkylcyanamide” integration.

Solvent-free N-iodosuccinimide-promoted synthesis of spiroimidazolines from alkenes and amidines under ball-milling conditions

An environmentally benign and N-iodosuccinimide-promoted intermolecular cyclization between alkenes and amidines has been demonstrated under solvent-free ball-milling conditions, affording a variety of spiroimidazolines with remarkable functional group tolerance and good to excellent yields.

Mechanochemical synthesis of thioureas, ureas and guanidines

In this review, the recent progress in the synthesis of ureas, thioureas and guanidines by solid-state mechanochemical ball milling is highlighted. While the literature is abundant on their preparation in conventional solution environment, it was not until the advent of solvent-free manual grinding using a mortar and pestle and automated ball milling that new synthetic opportunities have opened. The mechanochemical approach not only has enabled the quantitative synthesis of (thio)ureas and guanidines without using bulk solvents and the generation of byproducts, but it has also been established as a means to develop "click-type" chemistry for these classes of compounds and the concept of small molecule desymmetrization. Moreover, mechanochemistry has been demonstrated as an effective tool in reaction discovery, with emphasis on the reactivity differences in solution and in the solid state. These three classes of organic compounds share some structural features which are reflected in their physical and chemical properties, important for application as organocatalysts and sensors. On the other hand, the specific and unique nature of each of these functionalities render (thio)ureas and guanidines as the key constituents of pharmaceuticals and other biologically active compounds.