Diaryl acetylene

The dihalocarbene method was expanded in scope and improved in yield by the introduction of carbenoids of several types. Thus, (dichloro-bromomethyl) phenyl mercury reacted with diaryl acetylenes giving diaryl cyclopropenones in high yields (60—... 

Two groups simultaneously found that trimethylsilyl cyanide reacts with disubstituted acetylenes in the presence of a Pd catalyst to form silylated 2-amino-5-cyanopyrroles 194 or 195 [133, 134], These reactions are run neat and a variety of Pd species are successful in this transformation [133]. In the case of unsymmetrical diaryl acetylenes, the reaction is not regioselective [134],... 

Scheme 2.6. DMSO as bulk oxidant in the HBr-catalyzed oxidation of a diaryl acetylene.

Dialkyl- and diaryl-acetylenes are selectively converted to a-diketones (equation 121), whereas terminal alkynes give the corresponding carboxylic acid with loss of one carbon atom.337... 

The ability of the ethynyl-l,5-azastibocines 5, to be used as alkynylation agents, has recently been demonstrated by Kakusawa et al. <2003TL8589>. The reaction of 5 with organic halides, such as acyl halides and aryl halides, in the presence of PdCl2(PPh3)2, as a catalyst, led to the formation of cross-coupling products, alkynyl ketones 109 and diaryl acetylenes 110, in good yields (Equations 9 and 10). 

Nova k et al. [75] synthesised 58 by palladium-catalyzed coupling of halogenated phenols (269) and acetylene (268). The resulting diaryl acetylene (270) underwent simultaneous cyclization upon removal of protecting groups as shown in Fig. (15). 

Selective hydrogenation is apparently best realized for dialkyl-la,b,2°3,298 and diaryl-acetylenes,286 and for compounds in which the triple bond is endocyclic,299 since in such cases further hydrogenation of the resulting olefins is markedly slower for instance, cyclodecene is obtained in 96% yield from cyclodecyne.296 The ethylene derivatives formed from monosubstituted... 

Propargyl alcohol, HC2CCH2OH is an important intermediate in the synthesis of 1,4-butandiol, furan, and THF from acetylene (Fig. 15). HC2CMe2(OH) is used in the synthesis of aryl- and diaryl-acetylenes or of carbamates. Dehydration-hydration reactions of cluster-bound propargyl alcohols will be discussed in this section, after a short glance at their behavior on mono- and binuclear complexes. 

Diaryl acetylenes usually react slowly with TADs in solution at room temperature to give bis(azomethine imines) 336 as products (84JOC2917). 1,3-Diaryl isobenzofurans 337 with TADs give very stable betaines 338, which do not undergo 1,3-dipolar cycloaddition [82JCS(CC)766], Pyrido-[l,2-fl]azepinone 339 treated with MTAD at room temperature gives a quantitative yield of a mixture containing mainly 342 accompanied by a... 

Solid state excitation of electron donor-acceptor complexes of various diaryl-acetylenes and dichlorobenzoquinone in either the acceptor or the 1 2 complex absorption bands induces [2+2] cycloaddition and produces identical mixtures of the quinone methides. Evidence is presented for the participation of an ion-radical pair as the reactive intermediate in both cases. Irradiation of an appropriately substituted o-hydroxybenzyl alcohol precursor generates the corresponding o-quinone methide which is reported to undergo an efficient [4+2] cycloaddition to form the hexahydrocannabinol system. Time-resolved studies confirm the intermediacy of the o-quinone methide and show its lifetime to be > 2 ms. Laser photolysis of 1,2-bis(phenoxymethyl)benzene, l,2-bis[(phenylthio)-methyl]benzene, and l,2-bis[(phenylseleno)methyl]benzene occurs by a two-photon process to produce o-quinodimethane which will cycloadd to various dienophiles including maleic anhydride, dimethyl maleate, dimethyl fumarate, fumaronitrile and dimethyl acetylenedicarboxylate. ... 

The quadratic NLO active molecules are mostly based on donor-acceptor substituted aromatics benzene, stil-benes, diaryl acetylenes, diacetylenes, and biaryls are commonly used frameworks. In addition to the above materials, many more organic and organometallic compounds were examined by the powder SHG method, or their molecular hyperpolarizabilities were measured using EFISHG/HRS techniques, or both.t >... 

Similar local anisotropic effects can mask the effect of bond polarization in diaryl acetylenes (tolanes). A number of ortho- and para-substituted tolanes have been examined to test the effect of alkyne polarization on the chemical shifts. " While bond polarization controls the relative chemical shifts in p-tolanes (more positive carbon displays a downfield shift), the trends in o-tolanes are complicated by the close proximity of the substiment to the alkyne (Figure 12.31). Local anisotropic contributions of orffto-substituents caused the alpha-afkyne carbon to display an upfield shift despite it-effects on alkyne polarization. 

P. Fritsch, Ann. 279, 319 (1894) W. P. Buttenberg, ibid. 327 H. Wiechell, ibid. 332. Carbene-mediated rearrangement of 1,1-diary 1-2-haloethylenes to diaryl acetylenes ... 

The cobalt catalyst is highly effective for the [2+2+2] cycloaddition of internal monoynes. For example, the [2+2+2] cycloaddition of a diaryl acetylene proceeded to give an oligoaryl, which is used as an electrochemical switch (Scheme 21.5) [8]. 

The versatile thallium(ni) nitrate (TTN) oxidizes acetylenes to different types of product, depending on the acetylene. Terminal acetylenes are converted into the carboxylic acid with the loss of a carbon atom, diaryl-acetylenes ve benzils, dialkylacetylenes give acyloins, and alkylarylacetyl-enes are oxidized in methanol to alkylaryl acetates (Scheme 3). ... 

Treatment of 1,1-diaryl-2-haloethylene with base affords diaryl acetylene via the intermediacy of alkylidene carbene. 

Terphenyls have been made by cyclisation of ketones in the presence of halogenotrimethylsilanes, as reported earlier,and also ° by the Diels-Alder reaction of diaryl-acetylenes (268) with 2,5-disubstituted 3,4-diphenylcyclo-pentadien-l-ones (269), yielding (270). 

Several new classes of novel poly(a l ether)s have been synthesized which have very high glass transition temperatures. Most of these polymers are soluble in solvents such as dichloromethane, chloroform or chlorobenzene at room temperature and they can be cast into flexible films. Poly(aryl ether)s containing phthalocyanine moietes have also beem synthesized. Methods have been developed to introduce reactive functionality, e.g diaryl acetylene and diaryl cyclopropane moieties, into the backbone of these polymers so that they can be thermally cross-linked after fabrication. 

Bosch, E., Hubig, S.M. and Kochi, J.K., Paterno-Buchi coupling of (diaryl)acetylenes and quinone via photoinduced electron transfer,/. Am. Chem. Soc., 120, 386,1998. 

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