Reagents alkynylation

Alkynyl anions are more stable = 22) than the more saturated alkyl or alkenyl anions (p/Tj = 40-45). They may be obtained directly from terminal acetylenes by treatment with strong base, e.g. sodium amide (pA, of NH 35). Frequently magnesium acetylides are made in proton-metal exchange reactions with more reactive Grignard reagents. Copper and mercury acetylides are formed directly from the corresponding metal acetates and acetylenes under neutral conditions (G.E. Coates, 1977 R.P. Houghton, 1979). 

The 2-(l-alkynyl)oxirane 78 reacts with an organozinc reagent yielding the /9-allenylic alcohol 79[35]. 

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). 

In recent years, tnflate derivatives of bivalent iodine have found more and more applications as versatile reagents in organic synthesis [7i5, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145] p.-Oxo-bi [(trifIuoramethanesulfonyloxy) (phenyl)iodine], which is readily available from lodosobenzene and tnflic anhydride (equation 44), is especially valuable for the preparation of alkynyl lodonium Inflates from silyl- or stannylacetylenes [136] (equation 70)... 

Another useful reagent for the preparation of alkynyl lodonium Inflates is [cyano(trifluoromethylsulfonyloxy)(phenyl)]iodine [/i7, 138, 139, 140] prepared from iodosobenzene, trimethylsilyl tnflate, and trimethylsilyl cyanide (equation 71). This reagent reacts with various stannylacetylenes under very mild conditions to form the corresponding alkynyl iodonium salts in high yields [139] (equation 72)... 

Alkynyl iodonium triflates prepared by the above reactions (equations 70,72, and 73) have become valuable reagents m organic chemistry, serving as premier... 

The polar tellurium(II)-nitrogen bond is readily susceptible to protolysis by weakly acidic reagents. Eor example, the reaction of [Te(NMe2)2]oo with two equivalents of Ph3CSH produces the monomeric thiolato derivative Te(SCPh3)2. Alkynyl tellurides may be prepared by the reaction of terminal acetylenes with arenetellurenamides (Eq. 10.13). ... 

Some recent studies have underlined the effect that certain physical properties of the reaction medium have in governing the nature and yields of the products obtained when indole Grignard reagents react with alkyl or alkynyl halides. Such factors include the basicity and dielectric constant of the medium and its ability to solvate any of the reacting species. ... 

The alkynyl reagent 9 was recently introduced for the dia stereoselective synthesis of tertiary propargylic alcohols144. 9 can be prepared as a solid 1 1 complex with tetrahydrofuran by treatment of 9-methoxy-9-borabicyclo[3.3.1]nonane with (trimethylsilylethynyl)lithium, followed by addition of boron trifluoride-diethyl ether complex. The nucleophilic addition of reagent 9 to (R)-2-methoxy-2-methylhexanal (10) afforded a mixture of the diastereomers 11 with a considerable preference to the nonchelation-controlled (3S,4R)-isomer144. 

Optically active alkynyl alcohols can, however, be conveniently prepared by the addition of dialkylzinc reagents of alkynyl aldehydes catalyzed by the chiral ligand (S)-l-methyl-a,a-diphenyl-2-pyrrolidine methanol33-34. 

Note Such halogenation can be done by addition of elemental halogen to alkenyl or alkynyl groups or by replacement of one or more of the hydrogen atoms attached to alkyl or aryl substituents, using a variety of reagents. 

In general, the reaction can be performed only with organometallics of active metals such as lithium, sodium, and potassium, but Grignard reagents abstract protons from a sufficiently acidic C—H bond, as in R—C=C—H —> R—C=C—MgX. This method is best for the preparation of alkynyl Grignard reagents. ... 

Unsymmetrical coupling of vinylic, alkynyl, and arylmercury compounds was achieved in moderate-to-good yields by treatment with alkyl and vinylic dialkylcopper reagents (e.g., PhCH=CHHgCl -t- Mc2CuLi PhCH=CHMe). Unsymmetrical biaryls were prepared by treating a cyanocuprate ArCu(CN)Li (prepared from ArLi and CuCN) with an aryllithium Ar Li. ... 

Allylic phosphonate esters react with imines, in the presence of a palladium catalyst, to give P-lactams. " Alkynyl reagents such as BuC=CO Li react with imines to form P-lactams. 

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