4-vinylimidazole

Reaction of the 3,4-dimethyl-1-phenylphosphole (L) complex [PdLjClj] with 1-vinylimidazole in the presence of silver perchlorate carried out in... 

Pd(OAc)2 works well with strained double bonds as well as with styrene and its ring-substituted derivatives. Basic substituents cannot be tolerated, however, as the failures with 4-(dimethylamino)styrene, 4-vinylpyridine and 1 -vinylimidazole show. In contrast to Rh2(OAc)4, Pd(OAe)2 causes preferential cyclopropanation of the terminal or less hindered double bond in intermolecular competition experiments. These facts are in agreement with a mechanism in which olefin coordination to the metal is a determining factor but the reluctance or complete failure of Pd(II)-diene complexes to react with diazoesters sheds some doubt on the hypothesis of Pd-olefin-carbene complexes (see Sect. 11). 

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)]. 

Additions to /V-alkeny I imidazoles are influenced by conjugation with the heteroring (Equation 9) a vinyl group is not cleaved when l-vinyl-3-alkyl quaternary salts are thermolyzed and 1-vinylimidazole is not subject to thermal rearrangement (80AHC(27)24t, 82CHEH90,84JHC133). 

Several monomers of water-soluble polymers were analyzed with the help of the proposed two-dimensional diagram (Figs. 4 and 5, Scheme 1). In Fig. 4, the data for four synthetic monomers, N-vinylcaprolactam (VCL), N-vinylpyrrolidone (VP), AT-isopropylacrylamide (NIPA), and 1-vinylimidazole (Vim), at different temperatures are presented, and in Fig. 5, the data for eight amino acids are shown. 

Fig. 18 Reaction rate of hydrolysis of p-nitrophenyl acetate as a function of inverse temperature. Thermosensitive imidazole-containing copolymers (PVCL-Vim, PNIPA-Vim), 1-methylimidazole and poly(l-vinylimidazole) act as catalysts. Numbers in the copolymer abbreviations denote the Vim content (in mole percent). Vim 1-vinylimidazole. (Adapted from Ref. [18])...

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. 

VINYL-dl-HOMOCYSTEINE see VLU200 VINYUDENE CHLORIDE see VPKOOO VINYLIDENE CHLORIDE (II) see VPKOOO VINYUDENE DICHLORIDE see VPKOOO VINYUDENE DIFLUORIDE see VPPOOO VINYUDENE FLUORIDE see VPPOOO VINYLIDINE CHLORIDE see VPKOOO 1-VINYLIMIDAZOLE HOMOPOLYMER see VPPlOO N-VINYUMIDAZOLE HOMOPOLYMER see VPPlOO N-VINYUMIDAZOLE POLYMER see VPPlOO... 

Thermal rearrangement of 1-vinylimidazole gives a 7 1 ratio of 2- and 4-vinyl isomers. Similar treatment of 1-allylimidazole gives about equal quantities of the 2- and 4-allyl compounds. Irradiation at 300 nm transforms trans-1-styrylimidazole into the cis isomer (247) which then photocyclizes to (248 Scheme 140) (76JCS(P1)75). 

The life time of the O2 adduct is 12 min giving the oxidized complex. But this is the first success to have reversible oxygen binding in aqueous solution for some minutes. Also using coordina-tively bound (11) at a copolymer of styrene and 1-vinylimidazole in HjO saturated toluene ti/2 is 12 min. 

The copolymerisation of (J5), (36) and (38) was carried out with styrene (also terpoly-merisation with 1-vinylimidazole) and n-lauryl-methacrylate (Table Mixing of CO- copofymeiisation... 

The first example for Method 2 was reported by Nishide and co-workers, who polymerised a metal complex of 1-vinylimidazole with l-vinyl-2-pyrollidone and divinylbenzene [8]. The metal-vinylimidazole complex was copolymerised, cross-linked with l-vinyl-2-pyrollidone by y-ray irradiation and the template metal ion was removed by treating the polymer complex with an acid. These poly(vinyl-imidazole) (PVI) resins adsorbed metal ions more effectively than the PVI resin prepared without the template. The number of adsorption sites and the stability constant of the Ni(II) complex were larger for the PVI resin prepared with the Ni(II) template, as seen by the smaller dissociation rate constant of Ni(II) from the resin. 

Previous routes to such compounds have included dehydration of 2-(j8-hydroxyethyl)imidazoles [55] (or dehydrobromination of the analogous bromoethyl compounds), pyrolysis of 2-(5-norbomen-2-yl) imidazoles [57] or thermal rearrangement of 1 -vinylimidazoles [58],... 

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