Diphenylacetylene formation

The phosphine complexes provide a thermal route to other molybdenocene adducts since the molybdenum-phosphorus bond appears to be labile. When solutions of [Mo(7 5-C5H5)2PEt3] react with CO or diphenylacetylene, formation of the corresponding adduct results (see Reaction 11). 

The reaction of alkoxyarylcarbene complexes with alkynes mainly affords Dotz benzannulated [3C+2S+1C0] cycloadducts. However, uncommon reaction pathways of some alkoxyarylcarbene complexes in their reaction with alkynes leading to indene derivatives in a formal [3C+2S] cycloaddition process have been reported. For example, the reaction of methoxy(2,6-dimethylphenyl)chromium carbene complex with 1,2-diphenylacetylene at 100 °C gives rise to an unusual indene derivative where a sigmatropic 1,5-methyl shift is observed [60]. Moreover, a related (4-hydroxy-2,6-dimethylphenyl)carbene complex reacts in benzene at 100 °C with 3-hexyne to produce an indene derivative. However, the expected Dotz cycloadduct is obtained when the solvent is changed to acetonitrile [61] (Scheme 19). Also, Dotz et al. have shown that the introduction of an isocyanide ligand into the coordination sphere of the metal induces the preferential formation of indene derivatives [62]. 

The symmetric diarylthiirene oxides (18) are much more thermally stable than the corresponding saturated thiiranes and unsaturated thiirene dioxides. Thus, the thiirene oxide 18a shows only slight decomposition after 24 hours of reflux in benzene, whereas the analogous sulfone 19b fragments completely to SO2 and diphenylacetylene after less than six hours under the same conditions Irradiation of the oxide 18a, however, does result in the elimination of sulfur monoxide and formation of diphenylacetylene. Its thermolysis at 130 °C afforded benzil as the only isolable product, implying that SO is not being eliminated in this thermolytic process. 

Formation of the metaphosphonate 23 also occurs on mass-spectrometric fragmentation of the 1,3,4X5-dioxaphosphorin 56a 17 35> a peak at m/e = 140 corresponding to the mass number of 23 is indeed observed 35). Vacuum pyrolysis of 56a parallels the mass spectrometric degradation to form diphenylacetylene and benzophenone however, 23 could not be detected directly. This can be accomplished though, if thermolysis is conducted in methanol (220 °C/22 at) dimethyl benzenephosphonate (63) is again formed via 62 35). 

Typical examples are the formation of 3-chloro-2-phenylbenzo[b]-thiophene (21) in near quantitative yield from diphenylacetylene at room temperature,27 and the synthesis of the dichlorothianonane (22) from 1,5-cyclooctadiene.28... 

The formation of highly substituted titanacyclobutenes utilizing titanocene-alkylidenes has been investigated (Scheme 14.33). Alkylidenetitanacyclobutenes 76 are produced by the reaction of titanocene-alkenylidene complexes with alkynes [76]. The alkenylcydopro-pane 77 can be synthesized by thermolysis of dicydopropyltitanocene in the presence of diphenylacetylene, which is assumed to proceed through formation of the titanacyclobutene 78 [25c],... 

The reaction chemistry of germyne 172 has been investigated. Reaction with diphenylacetylene produces the digermacyclobutadiene 179 (Equation (326)), while treatment with excess trimethylsilylacetylene affords the bicyclic compound 180 (Scheme 69), which results from the formation of a biradical intermediate.394... 

The formation of transient 1,2-digermacyclobutadiene 9179 was postulated in the reaction of TsiGeCl LiCT 3THF78 with Mg in the presence of diphenylacetylene. This reaction could involve the formation of the digermyne intermediate 92 generated from 93 formed by dimerization of the germylene anion radical 94 [Eq. (18)]. 

Benzenecarhodithioesters and carbo-thio-S-esters were shown to yield diphenylacetylene by the cathodic reduction in aprotic media. Thus, the formation of diphenylacetylene involves [202] two molecules of a substrate. The cathodic reactivity of thioamides involving a similar alkylation of the C=S group in the presence of primary alkyl halides was reviewed [199-201]. 

The disodium salt of diphenylacetylene dianion is stable in THE solution at -78°C. Methanol acts as a proton source toward the salt and causes the formation of a mixture of 1,2-diphenylethane with diphenylacetylene and small amounts of tran -stilbene (Chang and Johnson 1965, 1966). It seems logical that the reaction between (PhC=CPh) , 2Na and MeOH leads at first to PhCH=CHPh. The second step is supposed to consist of the further reduction of PhCH=CHPh at the expense of electrons from the nonreactedpartof the initial dianion. In principle, the electron transfer may proceed faster than the reaction of the initial dianion with protons. As a result, the diphenylacetylene dianion has to discharge into diphenylacetylene, whereas stilbene dianion has to form diphenylethane as follows ... 

Bassett, J.-M., Green, M., Howard, J.A.K. and Stone, F.G.A. (1978) Formation of nona(ethyl isocyanide)diiron from penta(ethyl isocyanide)iron and reaction of penta(tert-butyl isocyanide)iron with diphenylacetylene X-ray crystal structures of nona(ethyl isocyanide)diiron and tris(tert-butyl isocyanide) l,4-bis-(tert-butylimino)-2,3-diphenylbuta-l,3-diene ... 

Boger et al. reported the first total synthesis of ningaline D (282) starting from the diphenylacetylene 1092 and dimethyl l,2,3,4-tetrazine-3,6-dicarboxylate (1093) (687). In this synthesis, the key step is the formation of the fully substituted pyrrole core using an inverse electron demand heterocyclic azadiene Diels-Alder reaction followed by a reductive ring contraction of the resultant 1,2-diazine. 

Thiatriazoles are generally not characterized by cycloaddition reactions. Neunhoeffer et al. were not able to induce a reaction between 5-phenyl-1,2,3,4-thiatriazole (7) and 1,2-diphenylacetylene or dimethyl acetylenedicarboxylate (36) even at 12 kbar <85LA1732>. Similar negative results are reported with other reagents (see Section 4.19.4.1). However, a reaction between 7V,A-diethyl-l-propynylamine (40) and 5-phenyl-1,2,3,4-thiatriazole (7) took place at 12 kbar and a compound assigned structure (41) on the basis of MS and NMR was isolated in 17% yield. The suggested reaction pathway, initiated by a 1,3-dipolar cycloaddition reaction at N(2) and N(4) is shown in Scheme 5. Formation of an alternative triazabicyclo[2.2.1]heptadiene was left open. 

The first derivative of 1,2,3-triazine to be prepared, the triphenyl compound (2, R = Ph), was obtained in 1960 by thermolysis of 1,2,3-triphenylcyclopropenyl azide (1, R = Ph)." The physical and spectral (IR and UV) properties of 2 were consistent with the assigned structure, and the presence of three contiguous carbon atoms was demonstrated by hydrolysis experiments, which resulted in formation of 1,2,3-triphenyI-butane-l,3-dione. Photolysis of 2 gave a mixture of nitrogen, benzo-nitriie, and diphenylacetylene. 

The alkyne relay, in particular, has frequently been used for cascade carbopaliadations with ring formation, because a carbon-carbon triple bond is more reactive toward carbopalladation than a carbon-carbon double bond. Thus, methyl -iodocinnamate 70 reacts with diphenylacetylene 71 to yield the methylenediphenylindene derivative 72 (Scheme 22). ... 

X-ray studies (193) on the complex derived from diphenylacetylene show that it has the structure (XXXV M = Co), in which th.e C—C bond of the acetylene is normal to the Co—Co bond. Although at a preliminary stage of refinement, the results also show that the configuration of the acetylene has changed considerably on complex formation, e.g., the C C bond has increased in length to 1.46A, and the Ph—O—C angle is no longer 180°, but 137°. 

The formation of 1,2,3,4-tetraphenyldihydrobenzene from diethylnickel and diphenylacetylene probably proceeds through an intermediate T-com-plex, e.g., [NiEt2(PRC C-Ph)2] 209) (cf. the reactions of acetylenes with triethylchromium in Section IV,B). 

The possible formation of a tctraphenylcyclobutadiencpalladium complex [PdCl2(Ci4H10)2] (XLVII), by treating palladium(II) chloride with diphenylacetylene in ethyl alcohol followed by hydrochloric acid (148, 149) has been mentioned in Section V,E. 

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