Group acetylides

There are a number of procedures for coupling of terminal alkynes with halides and sulfonates, a reaction that is known as the Sonogashira reaction.161 A combination of Pd(PPh3)4 and Cu(I) effects coupling of terminal alkynes with vinyl or aryl halides.162 The reaction can be carried out directly with the alkyne, using amines for deprotonation. The alkyne is presumably converted to the copper acetylide, and the halide reacts with Pd(0) by oxidative addition. Transfer of the acetylide group to Pd results in reductive elimination and formation of the observed product. 

To a three-necked flask equipped with a stirrer, condenser, thermometer, and dropping funnel is added an ether solution of 1.0 mole of n-butyllithium. Then a 50% ether solution of A-methyl-A-phenyltrichloro-l,l,2-enamine [16], b.p. 87°C (0.1 mm), nD 1.5859 (25), is added dropwise at —10°C under a nitrogen atmosphere until 0.42 mole has been added. The reaction is allowed to warm to room temperature in about 2 hr. The solution now possesses an intense absorption band at 2040-2050 cm-1, which is characteristic of the lithium acetylide group. 

The formation of carbene complexes by protonation of platinum(II) acetylides has been discussed. Both acetylide groups in frflns-Pt(C=CR)2(PMe2Ph)2 (R = H, Me) can be cleaved by HC1 (equation 222).616... 

Gold(I) acetylide complexes have been prepared from alkynyllithium compounds [Eq. (22)] (63), and a dimeric complex [(PhC=C)Au(/u.-dpe)-Au(C=CPh)] [dpe = bis(diphenylphosphino)ethane] was obtained analogously. The simplest acetylide complexes are perhaps those containing only acetylide ligands. The compounds [Au(C=CPh)]x and [Au(C=C-/-Bu)]4 (1) contain cr- and 7r-bonded acetylide groups, the values of... 

There has been reported a far-reaching extension, namely perchlorobutenyne 1 reacts with both 44 and 72 to give the corresponding trichlorovinyldiynamine 81 and tri-ynamine 82 (136) 36). Then the subsequent treatment with butyl lithium creates one more acetylide group. The interesting tri- and tetraacetylide intermediates 83,84 could be converted to esters 85 and 86 (137). 

The difference in nature of the final products from these two isomers has been related to the trans influence. In the cis isomer, both acetylide groups are equally labilized by the two phosphine ligands and are easily replaced by chloride. In the trans isomer, however, PtCl(C=CPh)-(PPh3)2 is obtained since the acetylide trans to the chloride is not replaced as a consequence of the lower trans influence of the chloride as against that of triphenylphosphine. The catalysis of the linear polymerization of phenylacetylene by PtHCl(PPh3)2 may also involve the insertion of an acetylene into the hydroplatinum bond 153, 115). 

Two poly(cyclodiborazane) polymers containing group-10 transition metal-acetylide groups P50 and P51 were prepared by Chujo et al. and represent a new kind of organometal-lic acetylide polymers functionalized with group-13 boron elements in the main chain.78 The structures of P50 and P51 were confirmed by IR and NMR ( H, 31P, and nB) spectra. The optical properties were studied by UV-vis absorption and emission measurements. It was shown that these polymers display extended -conjugation length via transition metal and boron atom with enhanced air- and moisture stability. 

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