Insertion reactions alkyne

Metal-promoted alkyne-insertion reactions afford another good method (see structure 12 for cluster geometry and numbering)... 

Because of the donor atom lability, the solvato complexes behave as coordinatively unsaturated species to the extent that they facilitate reactions such as alkene and alkyne insertion reactions and cleavage of B—C bonds. 

The cation trans-[PtH(CH3OH)(PEt3)2]+ is obtained from trans-[PtHCl(PEt3)2] by the general method just outlined.2 Its normal alkene and alkyne insertion reactions with methyl acrylate,3 diphenylacetylene,4 and... 

The alkyne insertion reaction is terminated by anion capture. As examples of the termination by the anion capture, the alkenylpalladium intermediate 189, formed by the intramolecular insertion of 188, is terminated by hydrogenolysis with formic acid to give the terminal alkene 192. Palladium formate 190 is formed, and decarboxylated to give the hydridopalladium 191, reductive elimination of which gives the alkene 192 [81]. Similarly the intramolecular insertion of 193 is terminated by transmetallation of 194 with the tin acetylide 195 (or alkynyl anion capture) to give the dienyne 196 [82], Various heterocyclic compounds are prepared by heteroannulation using aryl iodides 68 and 69, and internal alkynes. Although the mechanism is not clear, alkenylpalladiums, formed by insertion of alkynes, are trapped by nucleophiles... 

Heck (149) has discussed several alkyne insertion reactions involving alkyl- and acyl-tetracarbonylcobalt complexes. Most reactions seem to give tricarbonyl-7T-(penteno-4-lactonyl)cobalt complexes and numerous other products. The reaction of CFaC CCFs with HCo(CO)4 results in reduction of the alkyne (85), but Co2(CO)e(HC2H) is formed (150) in the related reaction of HC—CH with HCo(CO)4 in methanol. 

A recent report has described a series of Ni(0)-alkynylphopshine complexes (21) featuring the unusual coordination of the alkyne moiety in preference over the phosphine moiety (Scheme 20). The reaction of these Ni(0)-alkyne complexes with HCl and the isolation of the resulting Ni(ll) T] -vmy complexes (22) has provided a rare opportunity to study alkyne insertion reactions. The Ni-P bond in (22) undergoes another insertion see Insertion) by CO2 or CS2 to give 5-coordinate, zwitterionic see Zwitterion) complexes (23). 

As discussed in 11.3.3.1 a molecular orbital calculation favors cis coplanar geometry for 1,2-insertion of an olefin into the metal-alkyl bond of d metals. Although similar behavior is expected for alkyne insertion reactions, the assumption of a coplanar transition state may not be valid because of the greater availability of alkyne n orbitals . Experimental evidence for the coplanar transition state was obtained in a study of the kinetics of reactions (1) and (m). 

The reactions of bis(alkynyl)metallocenes Cp2M(C=CR)2 (M = Zr, Hf R = Me, Pr11, Bu11, Gy) with B(C6F5)3 afford the corresponding metallocene borate betaines of structure type 760.586 An assumed intramolecular alkyne insertion reaction leads to their less stable methylenecyclopropene-derived isomers, which are effectively trapped by the added / /7-butylisocyanide to yield complexes 764 which contain a methylenecyclopropene derived [Pg.906]

The equivalent alkyne-insertion reaction with PhC = CR (R = H or Ph) gives only -vinyl products, whereas RCH2C = CH (R = H or "Pr) gives f/ -vinyl and metallafuran products, though the same substrate with HC = CH yields exclusively the ethylidyne complex Tp W( = CMe)(CO)2. For the latter, an identical reaction course resulted from stoichiometric addition of Li[HBEt3] to a tetrahydrofuran solution of [Tp W(HC = CH)(CO)2][OTf] and this complex may also be prepared by an alternative route involving elaboration of an alkylidyne ligand (vide infra). ... 

A tunable rhodium-catalyzed intramolecular alkyne insertion reaction proceeding through the C-C cleavage of benzocyclobutenones was used to synthesize a variety of fused P-naphthol and indene scaffolds with dihydrobenzo[c]furan motifs (14AGE1674). 

Y. Li, P. J. Carroll, L. G. Sneddon, lonic-hquid-promoted decaborane dehydrogenative alkyne-insertion reactions a new route to o-carboranes. Inorg. Chem. 2008,47, 9193. 

Guram AS, Jordan RF. Alkene and alkyne insertion reactions of cationic Cp2Zr (l] -pyridy])(L) complexes. Zirconium-mediated functionalization of pyridines. Organometallics. 1991 10 3470-3479. 

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