Benzimidazole 2-vinyl

Vinyl methyl benzimidazole Vinyl methyl dichlorosilane Vinyl methyl oxazolidinone Vinyl oxyethylurea Vinyl propionate Vinylpyridine Vinyl siloxane Vinylsuccinimide Vinyl stearate... 

The vinyl group has been used to protect the nitrogen of benzimidazole during metalation with lithium diisopropylamide. It is introduced with vinyl acetate [Hg(OAc)2, H2SO4, reflux, 24 h] and cleaved by ozonolysis (MeOH, —78°). ... 

Similarly, pyrrole, indole, and tetrahydrocarbazole [285] as well as diarylamines give the corresponding N-vinyl compounds [286]. Several improvements of yields and reaction rates were observed by conducting the reactions in the presence of additives [287, 288]. The vinylation of imidazole and benzimidazole was reported to be catalyzed by KOH in the presence of zinc or cadmium salts [289]. The above reactions were reviewed in 1965 [290]. 

This comprises a copolymer containing 72 to 95 wt.% of ethylene and 28 to 5 wt.% of vinyl acetate and a small amount of organic composite having a bactericidal action contained therein, which is composed mainly of N,N-dimethyl-N -phenyl-N -(fluorodichloromethylthio)sulphamide, 1,2-benzisothiazoline-3-on, diiodomethyl-p-tolylsulphone and methyl(benzimidazol-2-yl)carbamate. It is suitable as cushioning material for floors and walls and as a material for building blocks and babies toys. 

Reppe has shown that secondary amines of low basicity, such as carbazole, diphenylamine, indole, imidazole, and benzimidazole, and amides such as pyrrolidone react with acetylene in the presence of strong alkali to give vinyl derivatives [81, 83, 84a, b] (Eq. 30). As described by Reppe, these reactions are... 

Whereas UL 94 delivers only a classification based on a pass-and-fail system, LOI can be used to rank and compare the flammability behavior of different materials. In Figure 15.2 the increasing LOI values are presented for different polymers as an example POM = poly(oxymethylene), PEO = poly(ethyl oxide), PMMA = poly(methyl methacrylate), PE = polyethylene), PP, ABS, PS, PET = polyethylene terephthalate), PVA = poly(vinyl alcohol), PBT, PA = poly(amide), PC, PPO = poly(phenylene oxide), PSU, PEEK = poly(ether ether ketone), PAEK = poly(aryl ether ketone), PES, PBI = poly(benzimidazole), PEI = poly(ether imide), PVC = poly(vinyl chloride), PBO = poly(aryl ether benzoxazole), PTFE. The higher the LOI, the better is the intrinsic flame retardancy. Apart from rigid PVC, nearly all commodity and technical polymers are flammable. Only a few high-performance polymers are self-extinguishing. Table 15.1 shows an example of how the LOI is used in the development of flame-retarded materials. The flame retardant red phosphorus (Pred) increases... 

Contributions of both the hydrophobic and the coulombic interaction are indicated in the hydrolyses of 3-nitroacyloxy benzoic acid (8) by poly(5(6)-vinyl-benzimidazole) (67) and of 3-acyloxy-N-trimethylanilinium iodide (acyloxy group in lieu of acetoxy group in ANTI (6)) by poly(5(6)-vinylbenzimidazole-co-acrylic acid), poly(BI-ac) (68). 

Alkenyl groups in A-alkenylazoles act as weak or moderate -electron acceptors. Thus, the basic pKa of 1-vinylimi-dazole (5.14) is nearly 2 pK units lower than that of imidazole. Examination of 1SN NMR spectra of 1-vinylimidazoles and -benzimidazoles shows that the nitrogen attached to the vinyl group resonates in at a higher field than N(3). In accord with these results 1-vinylimidazoles form less stable complexes with transition metals than 1-alkylimidazoles. 

The chemical behavior of benzimidazolylethylimidazolium salts 44 under basic and neutral media has been reported (92CL2357, 92MI2). As outlined in Eq. (34), deprotonation of compounds 44 afforded the fairly unstable ethyleneimidazolium benzimidazolate betaines 25 (but less so than 24), which underwent a type of /3-elimination at 80°C and 2-vinyl-benzimidazoles 68 were formed. 

In the same reaction conditions, betaine 145 underwent j8-elimination, providing 2-vinyl-benzimidazole 147, whereas its corresponding benzimi-dazolylethylimidazolium tetrafluoroborate 146 resulted in clean conversion to the aforementioned 1,5-diazocine 143 (92CL2357) [Eq. (37), (38)]. Moreover, betaine 145 was transformed to 147 as mentioned above, but its immediate precursor 146 gave 147 in low yield [Eq. (39)]. 

Reactions of alkynes with benzimidazole are also electrophilic processes. Thus, 1-vinyl-benzimidazole and 1,3-divinylbenzimidazolinone are formed by the addition of acetylene in aqueous dioxane at 160 and 200 °C to benzimidazole and benzimidazolinone, respectively. There is rather more complication involved in the reactions of such alkynes as dimethyl-acetylene dicarboxylate (DMAD) (see Section 4.07.1.8) with not only products of Af-alkylation, but also the formation of tricyclic products involved. 

UV studies suggest that in 1-vinyl-imidazoles and -benzimidazoles there is conjugation with the heteroaromatic ring. Certainly the reactivities of such compounds would indicate that they are not normal alkenes, nor are the alkynyl compounds typical of other alkynes. They are very prone to polymerization processes, and electrophilic addition reactions are often quite difficult to accomplish. When 1-styrylimidazoles are prepared, the trans compound is much more likely to eventuate as the more stable isomer 73CJC3765, 76JCS(PD545). 

Exposure of imidazole to normal Mannich conditions leads to A-(dimethylaminomethyl)imidazole, presumably via attack at the imine nitrogen, followed by loss of proton from the other nitrogen. A-Arylation or A-vinylation of imidazoles or benzimidazole can be achieved efficiently with metal catalysis (see 4.2). 

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