Alkynylzinc species

The zinc-cyanide complexes are on the interface of organic and inorganic chemistry. We include them here because of their Zn—C bond. (Perhaps this will encourage thermo-chemical investigations on the isoelectronic alkynylzinc species, much as there has been interest in both cyano and alkynyl silver-containing species. ) The species Zn(CN)2, Zn(CN)3 and Zn(CN)4 have all been thermochemically characterized in aqneons soln-tion by thermometric titration. The enthalpy of reaction values kJmoL are shown for reactions 9-11. 

Taken together, these observations suggest a reaction pathway involving an intermediate dialkyl alkynylzinc species which rearranges to the allenylzinc reagent by alkyl migration from zinc and internal Sjv2 displacement of the mesylate (equation 20). 

The synthesis of a new enantiopure, conformationally constrained 1,4-amino alcohol (25) has been reported, starting from commercially available reagents from the chiral pool.107 This 1,4-amino alcohol has been used as a chiral ligand in the addition of Et2Zn to aldehydes (best ee 98%) and in the synthesis of chiral propargylic alcohols (best ee 70%) by alkynylzinc species. 

A polymer with repeating 6,6 -dibutyl-BINOL units that are linked to each other at C-5 and C-5 has been synthesized. The Ti-complex of the polymer catalyzes the addition of alkynylzinc species to aldehydes. ... 

Use as a Dual Catalyst in Addition of Alkynylzinc Species to Aldehydes. A dual Lewis acid/base system was reported involving NMI, Ti(OiPr)4, and (/f)-BINOL in the enantioselective alkynylation of aldehydes with diethylzinc at room temperature. Other methods to access these products have been hindered by the need for higher temperatures to generate the alkynylzinc species. A variety of propargy lie alcohols could be prepared from aromatic aldehydes in high yields and with excellent enantioselectivities (eq42). ... 

Several derivatives of 4-aryl-l,5-disubstituted-1,2,3-triazole 51 were synthesized in good yields via 1,3-dipolar cycloaddition of aryl azides 48 and alkynylzinc species 49 followed by Negishi reaction of 50 under new conditions." Of all the combinations screened, Pd/xantphos was found to be superior. Kumada coupling was not as effective as the Negishi coupling in this reaction. 

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