Carbene-Mediated Transformations of 1-(Benzylideneamino)benzimidazoles

Abstract

Carbene-mediated transformations of N-(3-butylbenzimidazol-3-ium-1-yl)-1-arylmethanimine iodides with carbon disulfide and benzoyl isothiocyanate gave the corresponding NHC·CS(2) betaines in 68-85% and benzoyl-[1-butyl-3-[(E)-(aryl)methyleneamino]benzimidazol-1-ium-2-carbothioyl]azanides, respectively, in 74-85% yields. However, reaction with excess isopropyl isothiocyanate in NaH/THF at room temperature yielded the 1-butyl-1',3'-diisopropyl-3-[(E)-(aryl)methyleneamino]spiro[benzimidazole-2,5'-imidazolidine]-2',4'-dithiones (74-77%).

Triazaspirocycles: Occurrence, Synthesis, and Applications

“…Formation of NHCs can proceed via the corresponding metal-carbene complex [49], from the elimination of a haloform (CHX 3 ) [50], or from deprotonation of an imidazolium species [51, 52]. Elimination of carbamates, analogous to the urea elimination observed by Ulrich et al has been described as well in the synthesis of NHCs [53].…”

Recent advances in neutral and anionic N-heterocyclic carbene – betaine interconversions. Synthesis, characterization, and applications

“…Some additional compounds have been published meanwhile, such as the adduct of 1,2,4-triazol-5-ylidene with phenylisocyanate, 67 several fluoroalkyl-substituted imidazolium-2-carbodithioates 68 and 2-thiocarboxylates. 69 Benzimidazole / isothiocyanate adducts 70 and chemosensors based on the adduct formation of CO 2 to benzobisimidazolium carbenes 71 have also been described. In addition, a report deals with adduct formation of bis(N-heterocyclic carbene)s and bis(isothiocyanate)s.…”

Exploring the nucleophilicity of N,N′‐diamidocarbenes: Heteroallenes and related compounds as coupling reagents

“…These reactions are generally rapid, proceed with complete atom economy, and give high yields of products that are attractive for the synthesis of heteroatom rich compounds . Moreover, such carbene–heteroallene coupling reactions have been used in applications that range from small molecule activation and catalysis to the synthesis of novel polymers and heterocycles …”

“…[18,37] Moreover, such carbene-heteroallene coupling reactions have been used in applications that range from small molecule activation [23,24,38] and catalysis [39][40][41] to the synthesis of novel polymers [25,42] and heterocycles. [19][20][21][22]26,37,[43][44][45][46][47][48][49] Herein, we explore the nucleophilicity of a DAC (i.e., 1; Fig. 1) by evaluating its propensity to couple to various heteroallenes, including azides, isothiocyanates, isocyanates, and ketenes.…”

“…[61] Subsequent efforts were directed toward analyzing the reaction of 1 with isothiocyanates, substrates that typically afford imidothioates when exposed to NHCs. [44][45][46][47][48][49] Stirring a C 6 H 6 solution of 1 with an equimolar amount of 4-nitrophenyl isothiocyanate at room temperature for 1 h ([1] 0 = 0.13 M) resulted in the formation of dihydropyrimidinium imidothioate 3 (Scheme 2), as evidenced by the FT-IR carbonyl stretching frequencies observed at 1769 and 1740 cm À1 and the 1:1 DAC:isothiocyanate stoichiometry gleaned from 1 H NMR spectroscopic analysis of the crude reaction mixture. Pure 3 was isolated in high yield (96%) as a red-orange solid by recrystallizing the crude product from CHCl 3 /pentane, and the structural assignment was verified via single crystal X-ray diffraction (XRD) analysis ( Fig.…”