Phosphines alkynylation

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). 

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. ... 

C. Reactions not involving P=0 or P=S Groups.—Enamine phosphine oxides (45) have been prepared by the addition of amines to 1-alkynyl-phosphine oxides, and the reactions of their anions with various electrophiles have been reported. - With ketones a Wittig-type reaction leads to the formation of a/3-unsaturated ketones, in 53—70% yield, while with epoxides cyclopropyl ketimines are formed. A Diels-Alder reaction of l-phenyl-A -phospholen-l-oxide (46) with 1,4-diacetoxybutadiene has been used in the preparation of l-phenyl-benzo[/>]phosphole (47), as... 

Complexes of the type [AuRL] may contain a great variety of organic ligands such as alkyl, aryl, vinyl, or alkynyl, whereas the neutral donor ligand L is most commonly a tertiary phosphine. Also many polynuclear complexes are known which have the C-Au-L moiety with bridging polyfunctional ligands. Alkyl- or aryl-gold(I) complexes are usually synthesized... 

Anionic complexes of boron (boronates, borinates, etc.) have been introduced as convenient reagents in cross-coupling reactions of broad scope, particularly interesting for the transfer of alkynyl and primary alkyl residues, which cannot be accomplished using the standard protocols of the Suzuki-Miyaura reaction. Readily available Ph4BNa can be used as a convenient reagent for phenylation in place of the much more expensive PhB(OH)2, and all four phenyl groups can be utilized when the reaction is carried out with a phosphine-free catalyst in aqueous solutions.244... 

Although reports on silver(i) cr-alkynyl complexes have appeared for more than a century, the number of examples was still very limited prior to the past decade, and many of them were referred to as insoluble homoleptic polymeric [Ag(C=CR)]oo. Molecular alkynylsilver(i) complexes were often heteroleptic in nature and were achieved commonly through the stabilization by an extra coordination with strong cr-donor ligands such as amines, phosphines, and arsines. 

A related cyclization of 2-(alkynyl)phenylisocyanates with terminal alkynes to oxindoles was also reported by the same group (Equation (115)).472 (E)-exo-olefinic oxoindoles are selectively obtained. It was proposed that a palladium acetylide generated by the C-H activation of terminal alkynes regioselectively inserts to the alkyne moiety and the resulting vinylpalladium intermediate adds to the C=0 part of the isocyanate to give a (Z)-oxindole. This (Z)-isomer is isomerized to the ( )-isomer under the reaction conditions through catalysis of the phosphine. 

Reduction of the cyclic alkynyl carbonate 31 afforded two different products depending on the phosphine ligands on the palladium catalyst [48], Whereas Pd(dba)2/dppe gave the allenic product 32, the homopropargyl alcohol 33 was obtained with nBu3P (Scheme 3.16). 

Recently, Hiroi and co-workers reported a palladium-catalyzed asymmetric transformation of chiral 2-alkynyl sulfmates 142 into allenyl sulfones 145 (Scheme 4.38) [58], Treatment of 142 with Pd(OAc)2 in the presence of a phosphine ligand afforded allenylsulfones 145 with high stereospecificities (73-89%) in good yields, probably through intermediates 143 and 144. 

An interesting approach to allenyl thioethers has been reported by Huang and Xiong, which is based on a novel three-component reaction. Treatment of 1-alkynyl-phosphine oxides 310 with lithium alkylthiolates 311 in the presence of an aldehyde 312 provides the expected highly substituted allenyl thioethers 313 in good yield (Scheme 8.84) [173]. Unfortunately, this procedure could not be extended to arylthio-lates. 

Regiospeciflc, uncatalysed hydrophosphination of typical Michael acceptors, such as methyl acrylate, has been reported to proceed readily with alkenyl- an alkynyl-phosphine oxides, e.g. R(l )P(H)0. Good stereoselectivity was observed when a chiral electrophile was used. The reaction is believed to proceed owing to the strong... 

Phosphines, as nucleophiles, add to many unsaturated substrates giving metal-lated ylides. Scheme 17 collects some representative examples of the addition of phosphines to carbyne complexes, giving (57) [132], to allenylidenes (58) [133], a-alkenyls (59) [134], or a-alkynyls (60) [135]. Moreover, reaction of phosphines with 7i-alkenes [136] and 71-aIkynes (61)-(64) [137-140] have also been reported. It is not possible to explain in depth each reaction, but the variety of resulting products provides an adequate perspective about the synthetic possibihties of this type of reactions. 

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