Pyridines 1.3- diynes

Cuprous chloride pyridine Diynes by oxidative coupling s. 16, 780... 

Terminal alkynes can be coupled by heating with stoichiometric amounts of cupric salts in pyridine or a similar base. This reaction, which produces symmetrical diynes... 

Pyridine compounds 45 can also be produced by the NHC-Ni catalysed cycloaddition between nitriles 43 and diynes 44 (Scheme 5.13) [16]. The SIPr carbene was found to be the best ligand for the nickel complex in this reaction. The reaction required mild reaction conditions and low catalyst loadings, as in the case of cycloaddition of carbon dioxide. In addition to tethered aUcynes (i.e. diynes), pyridines were prepared from a 3-component coupling reaction with 43 and 3-hexyne 23 (Scheme 5.13). The reaction of diynes 44 and nitriles 43 was also catalysed by a combination of [Ni(COD)J, NHC salts and "BuLi, which generates the NHC-Ni catalyst in situ. The pyridines 45 were obtained with comparable... 

Condensation of triallylborane with octa-l,7-diyne (130-140 °C, 3 h) followed by treatment with methanol afforded a mixture of stereoisomeric l,4-bis(3-methoxy-3-borabicyclo[3.3.1]non-6-en-7-yl)butanes 66a and 66b (Scheme 26). Hydroboration of the latter with H3B-THF in THF and heating under reflux for 2 h gave rise to a mixture of racemic bis-l-boraadamantanes 67a and meso-ioim 67b in 94% overall yield. Pure racemate 67a was isolated by crystallization from the reaction mixture (THF) and converted to the pyridine complex 64 whose structure was established by X-ray diffraction analysis. 

The THF adduct 70 (mp 147 °C) and pyridine adduct 71 (mp 178°C) of bis-l-boraadamantane with one CH2 bridge were synthesized by hydroboration-cyclization of the bis-bicycle 72, available from hepta-l,6-diyne (Scheme 28) . 

The cobalt-catalyzed cooligomerization of diynes with nitriles allows a simple one-step synthesis222 of condensed pyridine derivatives including difficultly accessible 5,6,7,8-tetrahydroisoquinolines223 The synthesis is a versatile one in that pyridines condensed with five- and seven-membered carbocyclic rings can also be achieved in moderate yield in similar fashion. Additional attractive features of this simple synthesis are the formation of condensed isoquinolines by the use of functionalized nitriles and the pronounced regioselectivity observed when dissymmetrical diacetylenes are employed (Scheme 148).222... 

Diynes react with nitriles and aldehydes in the presence of a nickel(0) complex to give pyridines and dienones, respectively (Scheme 93).448,448a,448b... 

Dimerization (oxygen with CuCl in pyridine) of E- and Z-4-FcCH=CH C6H4C=CH gave the E,E- and Z,Z,-diynes, respectively, in >95% yield. " ... 

An intermolecular coupling reaction between three organonitrile molecules and a silicon-tethered diyne is reported to give good yields of pyrrolo[3,2-f]pyridine derivatives <2004JA7172>. The reaction is promoted by a low-valent zirconocene species (Equation 13). 

If the reaction is carried out in the presence of an oxidizing agent, such as O, or a cupric salt dissolved in pyridine (a weak base), a different product is obtained. Under these conditions, oxidative coupling occurs to give a conjugated diyne ... 

When the [2+2+2] cycloaddition of 1,6-diynes occurred in the presence of C=C bonds or C=N bonds, substituted benzenes or pyridines were obtained in good yields [95-98]. For example, anthraquinones were produced by reaction of l,2-bis(propiolyl)benzenes with a variety of monoalkynes [95] (Eq. 74). 

An intramolecular rhodium-catalyzed [2+2+2] cycloaddition of diynenitriles <07OL1295> diyne esters <07T12853> and alkynevinyl oximes <07TL6852> also afforded pyridine versions of dihydrobenzo[c]furans. Trost prepared these pyridine derivatives employing a similar ruthenium-catalyzed cycloisomerization-6 cyclization route as depicted in the following scheme <07OL1473>. 

A limited number of enediynes have been prepared by the reaction of copper acetylides with diiodoethylene in pyridine or DMF -For example, trans-1,6-diphenyl-3-hexcnc-l,5-diyne (52) is obtained in 90% yield when copper phenyl-acetylide (51) and r/fl j-l,2-diiodoethylene are warmed in pyridine. It was reported... 

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