Phenylacetylene, reaction with

Phenylacetone, 54, 50 Phenylacetonitrile, 50, 20 Phenylacetylene, reaction with ethyl magnesium bromide,... 

Sodiiim phenylacetylene, reaction with p-nitrophenyl-propiolyl chloride, 615 Stilbazoles, -carboxy-prep-aration from pyridine aldehydes, 342, 343 stereochemistry, 342, 343 -cyano-preparation from pyridine aldehydes, 343 stereochemistry, 343 stereochemistry of, 348, 349 synthesis, 348, 349 Strecker reaction, preparation of 2-cyanomethylfurans, 666 Strecker synthesis, of pyri-dine-side chain nitriles, 362, 535-538 Streptonigrin, 626 Styryl isocyanates, reaction with ynamines, 639 6-Substituted-2,4-bis(alky 1-... 

Phenylacetylene gives 1-phenyI-l, l-difluoroethane on reaction with a large excess of hydrogen fluoride in ether at 0 C or, in better yield, in the gas phase over a mercuric oxide catalyst [/]. Allene affords 2,2-difluoropropane [/]... 

Although hexafluoro-l,3-butadiene is better known for its [2+2] reactions, its Diels-Alder reactions, particularly with electron-deficient alkenes such as acrylonitrile and perfluoropropene, are not unknown [9] The first report of a Diels-Alder reaction is with an acetylenic dienophile Although the major product of Us reaction with phenylacetylene is its [2+2] adduct, a 3 5% yield of products of a Diels-Alder reaction is also observed [123] (equation 103)... 

The reactivity of arylhalides in the acetylenic condensation sharply decreases in the series Ar—I, Ar—Br, Ar—Cl. The rate of reaction of phenylacetylene with iodo derivatives is 800 times higher than that of the reaction with bromo derivatives and is 10 higher than that of the reaction with corresponding chlorides (75JOM253). Taking into account the very low activity of halogenopyrazoles (66AHC347), the catalytic variant of acetylenic condensation mainly involves the most active iodo derivatives. 

Alkynes can also be arylated by the Meerwein procedure, as shown by Muller in 1949. The reaction of buta-l-en-3-yne (Scheme 10-47) was studied by Kheruze and Petrov (1960). Arylation at an sp2-hybridized carbon is obviously considerably faster than the analogous reaction at an sp-hybridized carbon. A mechanistically interesting case of a Meerwein reaction with phenylacetylene will be discussed later in this section. 

As far as we are aware, the azo coupling of an ethyne derivative was only investigated over half a century ago Ainley and (Sir Robert) Robinson (1937) investigated the reaction of phenylethynes (phenylacetylenes) with diazonium ions (Scheme 12-59). Unsubstituted phenylethyne did not give identifiable products with the 4-nitrobenzenediazonium ion, but with the more nucleophilic 4-methoxyphenyl-ethyne an azo compound (12.119) was formed. On reaction with water it gives an arylhydrazone of an a-ketoaldehyde (12.120). 

Pyrazinone bearing a phenylalkynyl substituent at position C-3, was prepared in 47% yield via Sonogashira reaction with 7 equiv of phenylacetylene in a mixture of toluene/triethylamine (2 1) using Pd[P(Ph3)2]Cl2 and Cul as the catalyst system (Scheme 37). 

These authors observed that in 80% aqueous ethanol, the rates were pseudo first order in bromostyrene, except for the P-NO2-isomer, which did not react even at 190° C. The products of reaction in the cases where X = NH2, CH3CONH, and CH3O were exclusively the corresponding acetophenones and, for X = H, 74% acetophenone and 22% phenylacetylene. Reaction rates were found to increase with solvent polarity as well as addition of silver ion, but they were independent of added triethylamine (except in the very unreactive p-nitro isomers, where in the presence of added amine, a second-order reaction ensued that resulted exclusively in p-nitrophenylacetylene as product). 

Naumberg, Duong, and Gaudemer (729) have studied the stereochemistry of the addition of various acetylenes to [Co (DMG)2py] in methanol. They found, as already noted by Schrauzer and Windgassen 163), that the main product from the reaction with phenylacetylene in alkaline solution (pH > 10.5) was the jS-phenylvinyl complex (PhCH=CHCo), formed by the trans addition of the Co(I) anion and a proton, i.e.. 

Phenylacetylene reacts with anhydrous perchloric acid at -180°C and forms an organic perchlorate, which decomposes violently at a temperature starting at -78°C. The following reaction has been suggested ... 

The reactivity of OsHCl(CO)(P Pr3)2 toward alkynes depends on the type of alkyne used. Whereas phenylacetylene, propyne, and acetylene react by insertion to give the five-coordinate alkenyl derivatives Os ( >CI I=CHR Cl(CO)(PIPr3)2 (R = Ph, Me, H),31,33 the reaction with methylpropiolate affords a mixture of Os C(=CH2)C(OMe)0 Cl(CO)(P,Pr3)2 and 0s ( )-CH=CHC02Me Cl(C0) (P Pr3)234 (Scheme 3), and tert-butyl acetylene and diphenylacetylene are inert. 

The hydride-methyl complex OsH(Me)(CO)2(P Pr3)2 reacts with electrophilic reagents. The reaction products depend on the nature of the reagent (Scheme 39). Whereas the reaction with iodine gives almost quantitatively the diiodide OsI2(CO)2(P,Pr3)2, the reaction with a five-fold excess of phenylacetylene does not lead to the formation of the previously mentioned bis-alkynyl complex... 

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