Diphenylethyne

Haloalkynes (R—C=C—X) react with ArSnBu3 and Cul to give R—C= C—Ar. Acetylene reacts with two equivalents of iodobenzene, in the presence of a palladium catalyst and Cul, to give 1,2-diphenylethyne. 1-Trialkylsilyl alkynes react with 1-haloalkynes, in the presence of a CuCl catalyst, to give diynes and with aryl triflates to give 1-aryl alkynes. Alkynes couple with alkyl halides in the presence of Sml2/Sm. Alkynes react with hypervalent iodine compounds " and with reactive alkanes such as adamantane in the presence of AIBN. ... 

Yong et al. developed a cobalt-catalyzed [2+2+2] cyclotrimerization of terminal alkynes in good yields in aqueous media (80/20 mixture of water and ethanol) at room temperature. A cyclopentadienyl cobalt complex bearing a pendant phosphine ligand was used as a catalyst (Eq. 4.59). The cyclotrimerization of internal alkynes resulted in lower yields and required an elevated temperature, most likely due to steric interactions. For example, cyclotrimerization of 2,5-dimethyl-3-hexyne gave hexaisopropylbenzene in 51% yield and the reaction of diphenylethyne resulted in a 47% yield of hexaphenylbenzene.112... 

Diphenylenemethane, f2 Diphenylethanedione, b35 Diphenylethanedione dioxime, b36 1,2-Diphenylethene, s9 Diphenylethyne, d742 Diphenylglycolic acid, b37 Diphenylglyoxime, b36... 

Dimethyl-l-nitro-l-butyne, 2395 Diphenylethyne, 3634 Di(l-propynyl) ether, 2326 Di(2-propynyl) ether, 2327... 

Hydroboration of alkenes in non-ethereal solvent has been reported using diborane generated in situ from a quaternary ammonium borohydride and bromoethane (see Section 11.5). Almost quantitative yields of the alcohols are reported [e.g. 1 ]. As an alternative to the haloalkane, trimethylsilyl chloride has also been used in conjunction with the ammonium borohydride [2]. Reduction of the alkene to the alkane also occurs as a side reaction (<20%) and diphenylethyne is converted into 1,2-diphenylethanol (70%), via the intermediate /ra 5-stilbene. 

Alkynes tend to be much less reactive than alkenes. For example, 1,2-diphenylethyne produces only 23% of the dichlorocyclopropene from its reaction with dichlorocarbene, compared with 96% of the dichlorocyclopropane obtained from rrans-stilbene under analogous conditions [4]. Conjugated eneynes react preferentially at the C=C bond with dihalocarbenes [18-20, 22, 38] and with dimethylvinylidene carbene [158],... 

Reactions of alkynes with xenon difluoride have not been widely investigated. Propyne reacts more slowly with xenon difluoride in the absence of a catalyst than propene, to form a complex product mixture with 33% 2,2-difluoropropene.26 Diphenylethyne treated with xenon difluoride in the presence of hydrogen fluoride forms 1,2-diphenyltctrafluoroethane in 50% yield, comparable yields of 1,2-dialkyltetrafluorocthanes are observed on treatment of 1,2-dialkyl-propenes with xenon difluoride in dichloromethane at room temperature.58... 

Diarylethynes react with elemental sulfur to give tetraarylthiophenes in good yields (Equation (3)) (93SUL273). Although the reaction requires rather forcing conditions, it is a practical method, e.g. diphenylethyne and elemental sulfur at 220-240°C affords tetraphenylthiophene. The method is also applicable to tetraarylselenophenes. 

That sulfides coordinate to palladium(II) more strongly than the corresponding sulfoxides has received an interesting confirmation in a study of the complexes (19)-(21) (R = 4-MeQjHt).149 The complex (19) is the best catalyst both for cyclotrimerization of diphenylethyne and for isomerization of allyl ethanoates. In both processes a vacant metal coordination site is essential and the thioether sulfur is too strongly bound (in 20 and 21) for facile dissociation. 

Exercise 31-4 The diphenylethyne complex with Pt(0), analogous to 12, has been shown by x-ray diffraction analysis to have C—C=C bond angles of about 140° and a central C-C bond distance of 1.32A. Explain which of the formulations, 11a, 11b, or 11c, seems most reasonable to account for the x-ray data for this complex. 

Diperchloryl-4,4-diphenoquinone, 3438 Diperoxyazelaic acid, 3183 Diperoxyterephthalic acid, 2920 Diphenylacetylene, see Diphenylethyne, 3627 Diphenylamine, 3498... 

Dimethyl-1 -nitro-1 -butyne, 2389 (Dimethylamino) acetylene, 1559 Diphenylethyne, 3627... 

Diphenylethyne reacts with 5,6-dihydropyran-2-one in the presence of Ni(PPh3)3I2, Znl2 and Zn powder to give 5,6,7,8-tetraphenyldihydroisocoumarin, the product of a [2+2+2] cycloaddition-dehydrogenation sequence (Equation 449) <1999JOC3663>. 

A [Mn(GO)5] mediated condensation of methyl propiolate and 1,2-diphenylethyne affords the organometallic pyrylium ion complex 1215 in poor yield (Equation 467) <2002OM3434>. 

Nickel catalysed ethylzincation of diphenylethyne to give ( )-( 1,2-diphenyM-butenyDethylzinc and its conversion to ethyl ( )-2-methylene-4,5-diphenyl-4-heptenoate by copper promoted coupling with ethyl a-(bromomethyl)acrylate6Z... 

R = R1 = Ph) in very high yield by photolysis, the pyrazole is formed in only 3 % yield from diphenylethyne.50) The formation of cyclopropenes from pyrazoles apparently occurs via the corresponding diazo-compound. Thus photolysis of (53, R = R1 = Ph) at between 330 and 410 nm has been shown to lead to the diazo-compound (56) which on further photolysis or pyrolysis is converted to (54)50). Indeed, photolysis of vinyldiazoalkanes provides a good route to cyclopropenes thus photolysis of E- (57) leads to 3-alkoxycarbonyl-3-cyanocyclopropene51), while (58) leads either to the corresponding cyclopropene or to reversal to the pyrazole5Z). 

Scheme 1. Reaction of pentacarbonyl(a-methoxybenzylidene)chromium with diphenylethyne the first example of benzannulation.

The formation of side products depends on the choice of substituents and solvent [21]. The role of the solvent is illustrated by the reaction of phenyl carbene complex 1 with diphenylethyne (Scheme 7). An ethereal solvent such as THF leads exclusively to the benzannulation product isolated as quinone 7 after oxidative work-up, while use of the noncoordinating solvent hexane results in comparable amounts of cyclobenzannulation and cyclopentannulation products 7 and 8a. Strongly coordinating acetonitrile suppresses benzannulation product 7 in favor of the cyclobutenone 9, which is accompanied by minor amounts of cyclopentannulation products 8a and 8b. Indene 8a is obtained exclusively if the polar solvent DMF is employed. 

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