4 -Vinylimidazole, synthesis

This strategy was first realized by Lozinsky et al., who studied the redox-initiated free-radical copolymerization of thermosensitive N-vinylcaprolactam with hydrophilic N-vinylimidazole at different temperatures, as well as by Chi Wu and coworkers. Lozinsky presents an extensive review of the experimental approaches, both already described in the literature and potential new ones, to chemical synthesis of protein-like copolymers capable of forming core-shell nanostructures in a solution. 

Certain transition metal complexes can serve as templates for the synthesis of chelating NHC ligands. For example, 1-phenylphosphole complexes of pal-ladium(II) are attacked in a Diels-Alder reaction by 1-vinylimidazole. If 1,2-dichloroethane is used as the solvent the imidazole is alkylated in situ and then subjected to a spontaneous carbometallation reaction [Eq. (37)]. 

In another approaeh [88IJC(B)570], reaetion of 2-mereapto-4,5-di-p-tol-ylimidazole 43 with a-halo carboxylie acids enabled the synthesis of several imidazo[2,l-h]thiazoles. Acylative ring closure of 4,5-di-p-tolylimidazo-2-thioacetic acid (44, R = H) or 2-thiopropionic acid (44, R = Me) provides 5,6-di-p-tolylimidazo[2,l-h]thiazole-3(2//)-one (45, R = H) or its 2-methyl analog (45, R = Me). The synthesis of annelated imidazo[2,l-h]thiazoles (e.g., 46) can be achieved in one step by reaction of 2,3-dichloroquinoxaline with 43. The intramolecular eyelization of l-vinylimidazole-2-thiones to 2,5-dimethyl-3,6-arylimidazo[2,l-h]thiazoles with excellent yield has been reported (93T6619). 

The approach of synthesizing a monomer containing the desired functional group followed by (co)polymerization can be illustrated for the poly[4(5)-vinylimidazole] catalyst (VII) described in Sec. 9-lj. Synthesis involves the sequence of reactions starting from histidine (XXXVII) to yield 4(5)-vinylimidazole (XXXVIII), which is subsequently polymerized by radical initiation [Overberger and Vorchheimer, 1963],... 

A few syntheses of alkenic nitrogen compounds based on the rDA reaction are known. For example, ynamine (19), via rDA decomposition under FVP conditions, gives l-N,N-diethylamino-3-buten-l-yl (20). 2-Vinylimidazoles had previously been obtained by lengthy reaction schemes with low yields however, a practical laboratory synthesis of 2-vinylimidazoles based on a DA-rDA scheme has been developed. The DA adduct of acrolein and cyclopentadiene was converted to 2-(5-norbomen-2-yl)imida-zole (21), which was readily transformed into 2-vinylimidazole (22) as depicted in equation (16). Glyoxal gave the best result, but other a-dicarbonyl compounds could be substituted to obtain various 2-vinylimidazoles. 

Similarly, substimtion of allylamine for benzylamine in the process gives a useful, one-pot synthesis of 2-vinylimidazoles in 40-65% yields... 

Horner-Wadsworth-Emmons Reactions of Phosphonate Anions. - As with the Horner modification of the Wittig reaction, the principal focus of papers that mention the Horner-Wadsworth-Emmons reaction relate to synthetic applications. The use of pressure to induce the synthesis of P-amino esters, p-thioesters and P-thionitriles via tandem Horner-Wadsworth-Emmons and Michael reactions has been reported. The reagent (l-tritylimidazol-4-yl)methylphosphonate (99) has been prepared and, when treated with aldehydes and ketones, affords (E)-vinylimidazoles in high yields. ... 

A roundabout strategy may be necessary in a number of cases where the alkylation step is not compatible with the electrophilic reagent used, thus making protective groups necessary. A good example of this kind of methodology is the synthesis of imidazolium substituted mono or bis-phosphines from 1-vinylimidazole (Scheme 5.5-11) [28]. 

For this purpose they used 1-vinylimidazole as a versatile building block for the synthesis of cationic phosphines potentially attractive for hydroformylation in ILs. 

The synthesis of a well defined block copolymer, containing a poly(N-vinylimidazole) block (PVim), has been demonstrated by Ge et al. [23]. The polymerization was realized via a RAFT procedure employing xanthates as chain transfer agents. Initially, the polymerization of NIPAM monomer, affording PNIPAM macro-CTA, was realized followed by the polymerization of Vim, Figure 4. The obtained block copolymers had controllable molecular characteristics with a Mw/M value ca. 1.2. The living nature of the Vim polymerization has been confirmed by kinetic experiments, for the first 150 min of the polymerization reaction. It has to be noted that the above procedure was the first example of the synthesis of PVim containing block copolymers. 

Fig. 8 Synthesis of poly(l-vinylimidazole) (a) and polymer-grafted magnetic particles (b). Reprinted with permission from [194]. Copyright 2004 American Chemical Society...

Asayama S, Hakamatani T, Kawakami H (2010) Synthesis and characbaization of alkylated poly(l-vinylimidazole) to control the stability of its DNA polyirai complexes fin gene delivery. Bioconjug Chem 21 646-652... 

The microgel particles used in present study are based on copolymer of vinylcaprolactam (VCL) and acetoace-toxye yl methacrylate (AAEM). As described in our previous studies the microgel particles possess heterogeneous stmcture and consist of AAEM-rich core and VCL-rich shell due to some peculiarities of the polymerization process [30], The use of small fraction of vinylimidazole (Vim) during VCL/AAEM microgel synthesis allows selective incorporation of Vim units in the... 

Bozknrt A, Karadedeli B (2007) Copolymers of 4(5)-vinylimidazole and ethyleneglycol methaoylate phosphate synthesis and proton ctmductivity properties. React Funct Polym 67 348-354... 

I. Yu., Grineva, L.G., Polishchuk, A.P., and Chernega, A.N., Products of quaternization of 4,4 -bipyridine with halogenated carboxylic acids. Synthesis, structure and photoreduction in the crystalline state, Russ. J. Gen. Chem., 68, 609, 1998 (d) Suzuki, M., Kimura, M., Hanabusa, K., and Shirai, H., Reversible color changes induced by photosensitized charge separation in partially quaternized poly(l-vinylimidazole)-bound ruthenium(ll) complex and viologen hlms, Eur. Polym. 

The histidine residue, of which the imidazole group is a component, in particular is involved in the intramolecular multiple catalyst reaction of hydrolases. The catalytic activity of vinyl pol3nners containing imidazole groups was initiated by Overberger (5) with the synthesis of poly[4(5)-vinylimidazole]. 

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