Nickel alkynylation

Table 2. Molecular second-order NLO results for nickel alkynyl and chloro complexes ...

Table 8. Molecular third-order NLO data for nickel alkynyl complexes ...

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). 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

The Kumada/Ishikawa group also investigated thermolytic reactions of alkynyl-polysilanes and silacyclopropenes in the presence of nickel catalysts and implicated a 1-silaallene-nickel complex as an intermediate in the reaction pathway... 

Electrochemically generated nickel is very selective for the reduction of aromatic nitro compounds into anilines, in which alkenyl, alkynyl, halo, cyano, formyl, and benzyloxy groups are not affected.84 Sodium sulfide has been used for the selective reduction of aromatic nitro group in the presence of aliphatic nitro groups (Eq. 6.44).85... 

Nozaki-Hiyama-Kishi (NHK) reactions215,216 are well known and often employed as a useful method for the synthesis of natural products by coupling of allyl, alkenyl, alkynyl, and aryl halides or triflates with aldehydes. The organochromium reagents are prepared from the corresponding halides or triflates and chromium(ll) chloride, and are employed in polar aprotic solvents (THF, DMF, DMSO, etc.). Subsequently, it was found that nickel salts exhibited a significant catalytic effect on the formation of the C-Cr bond217,218 (Equation (19)). 

Alkynyl enals cyclize on treatment with a stoichiometric amount of Ni(COD)2/TMEDA complex to give nickel enolates such as 193,436>436a These metallacycles react with electrophiles including methyl iodide and benzaldehyde to yield cyclopentenol derivatives (Scheme 91). 

Catalytic reduction of the C-alkenyl and -alkynyl substituents over palladium or Raney nickel can be effected without concomitant hydrogenation of the heterocyclic system to give the corresponding alkyl-pyrroles and -indoles (72HC(25-2)65, B-77MI30504). 

Surprisingly, there appear to be no examples of relevant nickel alkenyl compounds in the literature, nor is there any apparent reference to their unsuccessful pursuit. A single report describes the synthesis of an alkynyl complex, viz. the four-coordinate TplPr2Ni(C=CC02Me) (55),33 which was... 

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving d.v-1 -borylbul-1 -en-3-yne derivatives. 1-Arylalk-l-ynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached.45... 

R = alkenyl, aryl, allyl, benzyl, propargyl R = alkenyl, aryl, alkynyl, alkyl, benzyl, allyl The Negishi Coupling was the first reaction that allowed the preparation of unsymmetrical biaryls in good yields. The versatile nickel- or palladium-catalyzed coupling of organozinc compounds... 

Reaction of (diisopropylamino)chloroboryl ethers of alkynols (57) with alkynyl-stannanes (58) in the presence of nickel catalysts has been reported to afford formal f/ms-alkynylboration products (60), which could undergo the Suzuki-Miyaura coupling with organic halides. The 2-borylalkenylnickel(II) complex (59) was isolated as an intermediate in a reaction of the chloroboryl ether (57) with 1 equiv. of a nickel(0)-phosphine complex and characterized by X-ray crystallography.61... 

The synthesis of complex polycyclic molecules has been achieved by Montgomery et al. by cascade cyclization processes involving nickel enolates [40]. Up to three cycles could be generated in the intramolecular version of the reaction. Alkynyl enal or enone were first converted into their corresponding seven-membered cyclic enolates in the presence of Ni(cod)2/TMEDA [41 ]. These species could be trapped by electrophiles such as aldehydes. For example, upon treatment with the nickel catalyst, dialdehyde 32 afforded spiro-cycle 35 in 49% yield as a single diastereomer (Scheme 17). 

Reduction by Alkali Metals. This was the first reduction method successfully used it is particularly useful for reducing in liquid ammonia cyanides ( ), alkynyls (f 4 ), ammines (193) and ethylendiammines (192). The same reaction on phosphine compounds gives low yields because the reagents are insoluble in liquid ammonia (45). The zero valent nickel compounds with phosphites are obtained in good yield with the potassium graphite compound KCs (110). 

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