Phenyl-substituted acetylenic

Phenyl-substituted acetylenes 6 react with cesium fluoroxysulfate in methanol with a regioselectivity which is dependent on the structure of the acetylene.12... 

The first intermolecular hydroamination of an alkyne was reported by Uchimaru in 1999 [92]. It was found that Ru3(CO)i2 catalyzes the reaction of N-methylaniline derivatives with phenyl-substituted acetylenes in good yields (76-88%)(Scheme 8.31). 

The carbometallation can be performed intramolecularly leading in this case to an unsaturated diorganonickel species of type 47 which undergoes a rapid reductive elimination furnishing polyfunctional cyclopentylidenes of type 48 (Scheme 9-41). The syn-addition is proven by using a phenyl-substituted acetylenic iodide such as 49 [78]. 

In the presence of a catalytic amount of PdCh, Ar>,BiX2 (X=C1, OAc) couples with arylstannanes to give biaryls (Scheme 14.155) or, under a CO atmosphere, diaryl ketones (Scheme 14.156) [316]. Unsymmetrical biaryls are also prepared by Pd-catalyzed reaction of diaryliodonium salts with Ar3BiX2 [317]. Terminal acetylenes are phenylated by Ph3BiF2 under CuCl catalysis to afford phenyl-substituted acetylenes [318]. 

The regiochemistry can be controlled by the nature of the substituents. With a tri-methylsilyl-substituted acetylene, the trimethylsilyl groups are placed in a positions of zirconacyclopentadienes with excellent selectivity (Eq. 2.8) [20]. With a phenyl-substituted alkyne, regioselective reactions are usually observed, although in some cases a mixture of two isomers may be formed. 

The cobalt mediated homo Diels-Alder reaction of norbomadiene (560) with phenyl acetylene (568a), affording a phenyl substituted deltacyclene, demonstrated the potential of low-valent cobalt complexes as catalysts332. Lautens and coworkers327 extended the scope of this reaction and were able to synthesize a wide range of substituted deltacyclenes from alkynes 568 (equation 164, Table 33). The low-valent cobalt or cobalt(O) species to be used was prepared in situ by reduction of Co(acac)3 with Et2AlCl. Monosubstituted... 

The addition reaction of alkyl and/or phenyl substituted silicon hydrides to acetylenes has limitations mainly due to the hydrogen donation step (cf. Scheme 5.1). Reaction (5.17) shows that the replacement of Ph by MesSi group in silanes made the reaction easier, the effect being cumulative. Indeed, the reaction time decreased from 88 h for PhsSiH to 3h for (TMS)3SiH [39], together with the amelioration of yields, and a slightly better cis stereoselectivity. 

B-Bromo and B-iodo-9-borabicyclo[3.3.1]nonane add similarly in a cis fashion to terminal triple bonds 471 They do not react, however, with alkenes and internal acetylenic bonds. In contrast to the results mentioned above, phenyl-substituted chloroboranes (PhBCl2, Ph2BCl) do not participate in haloboration. Instead, the C—B bond adds across the multiple bond to form phenylalkyl-(alkenyl) boranes.466,468... 

Another class of heterocyclic compounds are silyl-substituted triazoles which can be obtained by the addition of TMS-azide 14) and manifold substituted acetylenes 1, 35, 350 (Scheme 50)33,209 2ll Those in the first step resulting l-TMS-4-phenyl (3Ji)-, l-TMS-4,5-bis(methoxycarbonyl)- 352) and l-TMS-4-alkyl-l, 2,3-triazole 353) are then hydrolyzed to form 4-phenyl- 354)-, 4,5-bis(methoxycarbonyl)- 355), 4-alkyl-l,2,3-triazole 356). 

Nucleophilic attack of phosphines on 1,2,3-selenadiazoles leads to formation of selenophosphoranes and substituted acetylenes <2004CHE503>. Thus, 4-phenyl-1,2,3-selenadiazole 54 reacted with tributylphosphine in benzene at room temperature (Scheme 12). In the first stage, the Se-N bond is broken as a result of nucleophilic attack by tributylphosphine. Elimination of a molecule of nitrogen follows. A molecule of phenylacetylene is released from the intermediate and tributylselenophosporane 167 is produced. When triphenylphosphine is used, triphenylselenophos-phorane 168 is formed in quantitative yield after boiling for 1 h. In the reaction of 5-ethoxycarbonyM-mcthyl-1,2,3-selenadiazole 166 with phosphines, selenophosphoranes 167 and 168 are formed in 100% yield. Ethyl but-2-ynecarboxylate 169 was isolated from the reaction mixtures in 92% yield. 

The Diels-Alder reaction of 2-pyrones has been used in polymer syntheses (6, 13) (Reaction 4). In these reactions the 2-pyrone is difunctional in that it consumes two moles of dienophile (Reaction 16). A practical way of stopping at the 1 1 adduct is to use an acetylenic monomer (24) (Reaction 17). Although 2-pyrone itself polymerizes on standing (I), phenyl-substituted 2-pyrones, including monophenyl 2-pyrones, are stable at ordinary temperatures. 

As with the identity of the organic substituents R and the spacers Z, the electronegative substituents X and Y also have a profound influence on the structure of spacer-bridged tetraorganodistannoxanes. Like the parent compounds, enhanced kinetic stability in solution is observed for those cases in which the substituents are different (X Y). This is especially pronounced for the phenyl-substituted derivatives 39-43 (entries 1-5) and also valid for the acetylene-bridged compounds (entries 32-34). 

Phenyl substituted ethylenes, acetylenes, and allenes are known to add lithium metal — sometimes with dimerization — to yield stable benzyl-type 1,2- or 1,4-dilithium compounds, respectively. The first observations in this connection already go back to Schlenk and Bergmann in 1928. 

Another class of heterocyclic compounds are silyl-substituted triazoles which can be obtained by the addition of TMS-azide (14) and manifold substituted acetylenes 1, 35, 350 (Scheme 50) yj ose in the first step resulting l-TMS-4-phenyl... 

The bromochlorination of phenyl- and alkyl-substituted acetylenes with tetrabutylammonium di-chlorobromate gives (T)-olelins stercoselectively. Unsymmetrical disubstituted acetylenes give the preferred Markovnikov adducts, but the formation of zznZz-Markovnikov adducts is more pronounced with this reagent than with molecular bromine chloride, which is less stereoselective139. 

A selective cw-carboxylation was obtained with a dialkyl substituted acetylene (entry 8). With a phenyl and an alkyl substituent (entry 10) preferential carboxylation occurred at the alkylated carbon. Electron-deficient alkynes led to the saturated dicarboxylic acids (entry... 

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