Synthesis and Organocatalytic Applications of Imidazol(in)ium‐2‐thiocarboxylates

Abstract

Five imidazol(in)ium-2-thiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding imidazol(in)ium chlorides or tetrafluoroborates in a one-pot, twostep procedure involving the in situ generation of free Nheterocyclic carbenes (NHCs) with a strong base followed by trapping with carbonyl sulfide. The resulting NHC·COS zwitterions were isolated in high yields and characterized by IR and NMR spectroscopy. The molecular structure of SIMes·COS was determined by X-ray diffraction analysis. Experimental data and DFT calculations indicated that the negative charge on the thiocarboxylate anion is preferentially delocalized on the sulfur atom. Thermogravimetric

Probing the Diastereoselectivity of Staudinger Reactions Catalyzed by N‐Heterocyclic Carbenes

“…Another major difference between betaines 1 and 2 and the new compounds 3 and 4 is that the presence or absence of a CC bond in the NHC backbone of the former pair drastically altered the onset of their thermolysis, whereas it had only a slight influence in the latter case. In this respect, the thermogravimetric profiles of NHC ⋅ ketene adducts 3 and 4 match those determined previously for saturated or unsaturated NHC ⋅ CO 2 ,22 NHC ⋅ COS,23 and NHC ⋅ CS 2 zwitterions 24…”

Poly(ionic liquid)s based on imidazolium hydrogen carbonate monomer units as recyclable polymer-supported N -heterocyclic carbenes: Use in organocatalysis

“…Three different organocatalyzed reactions of molecular chemistry were implemented, namely, transesterification, benzoin condensation and cyanosilylation of aldehydes, known as being efficiently catalyzed by both molecular NHCs and ([NHC(H)][HCO 3 ]) salt precursors …”

“…Then, we examined the catalytic potential of poly([NHC(H)][HCO 3 ])s 4 for the benzoin condensation, a NHC‐catalyzed self‐condensation of benzaldehyde forming a β‐keto alcohol called benzoin . Reactions were carried out in THF for 24 h at 80 °C, in the presence of 10%mol.…”

Interaction of N‐Heterocyclic Carbenes and Simple Carbenes with Small Molecules (One to Three Atoms) Excluding Metals: Formation of Covalent C–X Bonds

“…Zwitterions resulting from the reaction between NHCs and COS . [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Zwitterions resulting from the reaction between NHCs and COS[128,129]. [Color figure can be viewed at wileyonlinelibrary.com] Adduct resulting formally from the reaction between an NHC and BeMe 2[139].…”