Alkynyl compounds, and

For the metal—alkyne fragmait, nonlinearity also increases upon increasing valence electron count [14 valence electron (triphenylphosphine) gold alkynyl compounds <18 valence electron (cyclopentadienyl) (triphenylphosphine)nickel, and (cyclopentadienyl) bis(triphenylphosphine) ruthenium alkynyl compounds] and increasing ease of oxidation (less easily oxidizable (cyclopentadienyl)(tri-phenylphosphine)nickel alkynyl complexes < more easily oxidizable (cyclopen-tadienyl)bis(triphenylphosphine)ruthenium alkynyl complexes). 

B. Xi and T. Ren (2009) Compt. Rend. Chim., vol. 12, p. 321 - Wire-like diruthenium a-alkynyl compounds and charge mobility therein . 

The synthesis of alkynylpalladium(ii) complexes usually proceeds through oxidative addition of a halo-alkyne or of a terminal alkyne to palladium(O) compounds, or by transmetallation employing main group alkynyl compounds and palladium(ii) halide precursors. Especially, the dialkynylpalladium complexes are of much interest as molecular inorganic materials because of their remarkable phase behavior and nonlinear optical properties. Several accounts and... 

Xi B, Ren T (2009) Wire-like dimthenium a-alkynyl compounds and chtiige mobility therein. Compt Rend Chim 12 321-331... 

This Grignard reagent has also been reacted with carbon dioxide and the cuprate of this Grignard reagent adds to alkynyl compounds and provides a practical synthesis of 1,3-butadienes (eq 4)M... 

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

Propargylic (or 2-alkynyl) compounds are derivatives of alkynes. However, Pd-catalyzed reactions of propargylic derivatives, particularly esters and halides, are very different mechanistically from those of simple alkynes, except in a few cases. Therefore, the reactions of propargylic esters and halides are treated in this section separately from those of other alkynes. However, some reactions of propargylic alcohols, which behave similarly to simple alkynes, are treated in Section 6. 

There is no way in which dehydration of alcohols can be used to prepare triple bonds gem-diols and vinylic alcohols are not normally stable compounds and vic-diols give either conjugated dienes or lose only 1 mol of water to give an aldehyde or ketone. Dienes can be prepared, however, by heating alkynyl alcohols with triphenyl phosphine. ... 

Liquid crystals based on aliphatic isocyanides and aromatic alkynyls (compounds 16) show enantiotropic nematic phases between 110 and 160 °C. Important reductions in the transition temperatures, mainly in clearing points (<100 °C), areobtained when a branched octyl isocyanide is used. The nematic phase stability is also reduced and the complexes are thermally more stable than derivatives of aliphatic alkynes. Other structural variations such as the introduction of a lateral chlorine atom on one ring of the phenyl benzoate moiety or the use of a branched terminal alkyl chain produce a decrease of the transition temperatures enhancing the formation of enantiotropic nematic phases without decomposition. 

In summary, [Au(alkynyl)(CNR)j complexes also show mesomorphic behavior but, in contrast to the halide-isocyanide derivatives, they are thermally less stable and usually decompose before or at the clearing temperatures. This thermal instability is thought to be associated with the gold-(alkynyl) bond and makes these compounds... 

The authors determined the optimal reaction conditions and illustrated the scope of the method with 32 different starting compounds including alkenyl-, alkynyl-conjugated and 2,2-disubstituted 1,1-dibromo-l-alkenes. 

Alkynyllead triacetates.1 Pb(OAc)4 reacts with a 1-alkynyltrimethyltin to form trimethyltin acetate and an unstable 1-alkynyllead triacetate (a), which can effect alkynylation of (i-dicarbonyl compounds and nitronates. In general yields are highest with R = QH, and lowest with R = H. 

Allenyl ethers are useful key building blocks for the synthesis of a-methylene-y-butyrolactones [129, 130], The synthesis of the antileukemic botryodiplodin was accomplished with the crucial steps briefly presented in Scheme 8.56. Bromoallenyl ethers 225 were easily prepared by base-induced isomerization from the corresponding /3-bromoalkyl alkynyl ether compounds and then subjected to electrophilic bro-mination with NBS. The resulting acetals 226 were converted into 2-alkoxy-3-methy-lenetetrahydrofurans 227 by dehydrohalogenation of the alkenyl bromide unit to an alkyne and subsequent radical cyclization employing tributyltin hydride [130],... 

Gevorgyan and co-workers demonstrated that allenyl imines can be formed in situ by treating alkynylimines with a base (see Section 15.8, compound 185) [71, 72]. The same principle also works for the in situ formation of allenyl ketones from alkynyl ketones and their conversion to furans with a copper(I) catalyst [71, 72]. That Cu(I) would catalyze the isomerization of an allenyl ketone was known from work of Hashmi et al. [57, 58],... 

In the hydroboration of terminal alkenes, carrying a ketone or aldehyde group, with a variety of borane reagents, dicyclohexylborane has been identified as the most efficient reagent. Analogous hydroboration of alkynyl ketones and alkynyl aldehydes with dicyclohexylborane yields the corresponding olefinic carbonyl compounds after protonation, or dicarbonyl compounds after oxidation. ... 

From alkynyl Grignard and lithium compounds and organyl tellurenyl halides... 

Carbonylative cross-coupling reaction between triarylbismuth(V) compounds and organostannanes is smoothly catalyzed by PdCl2 under 1 atm CO at room temperature (Scheme 48) [34]. Not only arylstannanes, but also heteroaryl-, alkynyl-, and vinyltributylstannanes were employed efficiently. 

Alkynyl Gngnard compounds and alkyl orthofonnates give acetylenic acetals in good yields. The reaction is usually canied out in Et20 [65) ... 

Cook and co-workers took advantage of the molybdenum-based methodology and reported one of the most graceful applications of the allenic PKR. They intended to use PKR to synthesize a theoretically interesting tetracyclic compound 55, which has 14 vr-electrons and is supposed to be aromatic in principle. To this end, they have applied PKR to various alkynyl allenes, and finally employed a diyne-diallene substrate 54 successfully (Equation (27)). Double PKR by employing molybdenum hexacarbonyl in excess and DMSO afforded the requisite intermediate in a high yield. 

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