4- Alkynyl imidazoles

Copper Reactants. 4-Alkynyl imidazoles are available from Al-protected 4-iodoim-idazoles and alkynes or alkynyltrialkyltin derivatives (Scheme 57). Reactions under Sonogashira conditions can be used to prepare the cross-coupled products 134. The same... 

Studies of alkenyl- and alkynyl-imidazoles in recent years have increased because of the interest in the polymerization of these compounds under the influence of free radical initiators. 

Iodoimidazole 371 coupled efficiently with TMS-acetylene 379 to produce 2-alkynyl-imidazole 380 in the presence of Cul and PdCl2(PPh3)2 at only 35 °C (Scheme 90) <2006JA4119>. 

Nina A. Nedolya was born in Irkutsk (Russia) and educated in organic chemistry at the Irkutsk State University (Diploma 1972, PhD 1982, DSc 1998). From 1995 to 1999 she was associated with Prof. L. Brandsma at the Utrecht University (The Netherlands). In 1999 she obtained her second PhD from the Utrecht University. She is presently Head of the Research Group of Chemistry of Heterocyclic Compounds at A. E. Favorsky Irkutsk Institute of Chemistry. She is the author of over 210 review articles and research papers. She is also one of the inventors for 112 patents. She is interested in the chemistry of polyfunctional unsaturated heteroatomic systems (vinyl, allenyl, and alkynyl ethers and their derivatives, linear and cyclic heteropolyenes, hetero-cumulenes), including synthesis of important heterocycles, particularly pyrroles, thiophenes, thiazoles, imidazoles, dihydrofurans, dihydropyridines, pyridines, quinolines, dihydroazepines, and azepines, based on metallated allenes or alkynes and/or heterocumulenes. 

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). 

Novel 2 -modified nucleoside triphosphate derivatives incorporating imidazole, amino or carboxylate pendant groups attached to the 5-position of pyrimidine base through alkynyl and alkyl spacers (115) have been synthesised. In one reported procedure, the appropriately protected modified nucleoside was phosphorylated with POCI3 in triethylphosphate in the presence of 1,8-bis(dimethylamino)naphthalene. The phosphorochloridate intermediate was then condensed in situ with tri-n-butylammonium pyrophosphate to yield the protected triphosphate analogue that was then deprotected. In another... 

Alkynyl(phenyl)iodonium salts have found synthetic application for the preparation of various substituted alkynes by the reaction with appropriate nucleophiles, such as enolate anions [980,981], selenide and telluride anions [982-984], dialkylphosphonate anions [985], benzotriazolate anion [986], imidazolate anion [987], N-functionalized amide anions [988-990] and transition metal complexes [991-993]. Scheme 3.291 shows several representative reactions the preparation of Ai-alkynyl carbamates 733 by alkynylation of carbamates 732 using alkynyliodonium triflates 731 [989], synthesis of ynamides 735 by the alkyny-lation/desilylation of tosylanilides 734 using trimethylsilylethynyl(phenyl)iodonium triflate [990] and the preparation of Ir(III) a-acetylide complex 737 by the alkynylation of Vaska s complex 736 [991]. 

Toste has reported the cyclization/rearrangement of aryl y-alkynyl sulfoxides catalyzed by a gold(I) N-heterocyclic carbene complex [90]. For example, treatment of phenyl 3-butynyl sulfoxide 52 with a catalytic 1 1 mixture of (IMes)Aud [IMes = l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] and AgSbFg led to isolation of... 

Fu et al. developed a room temperature, photoinduced, copper-catalyzed C—N Ullmarm coupling of electrophiles with nitrogen heterocycles (229- 231).The scope of allowed electrophiles is quite broad aryl halides, including hindered and deactivated examples, alkenyl halides, and alkynyl bromides are all tolerated. Indoles, benzimidazoles, and imidazoles can all undergo C-N coupling (13JA13107). 

---