4-Methyl-phenylacetylene

In order to exclude folding effects, three rigid aromatic terminal alkynes like phenylacetylene, 4-methyl-phenylacetylene, and 4-t-butyl-phenylacetylene, characterized by the same general shape but different lengths and electronic properties, were tested with the free and the encapsulated catalyst. In the bulk... 

The NMR spectrum of [III] is consistent with those, of [I] and [II], This is the only compound in the series in which the ligand is not symmetrical about the triple bond and, therefore, it is possible to have geometric isomers within the same basic structure. The methyl resonance line in pure methyl-phenylacetylene appears at 2,01 ppm below TMS, It was observed with the... 

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

It should be noted that a considerable acceleration of the reaction for low-reactive 4-iodopyrazoles is observed for substrates in which acceptor substituents at the pyrazole nitrogen atom additionally play the role of protecting group. Thus, it has been shown (88M253) that iV-phenacyl- and iV-p-tosyl-4-iodopyrazoles interact with phenylacetylene, 2-methyl-3-butyn-2-ol, and trimethylsilylacetylene at room temperature for 3-24 h in 70-95% yields (Scheme 56). 

The synthesis of 2-chloro-2,3,3-trifluorocyclobutyl acetate illustrates a general method of preparing cyclobutanes by heating chlorotrifluoroethylene, tetrafluoroethylene, and other highly fluorinated ethylenes with alkenes. The reaction has recently been reviewed.11 Chlorotrifluoroethylene has been shown to form cyclobutanes in this way with acrylonitrile,6 vinylidene chloride,3 phenylacetylene,7 and methyl propiolate.3 A far greater number of cyclobutanes have been prepared from tetrafluoroethylene and alkenes 4,11 when tetrafluoroethylene is used, care must be exercised because of the danger of explosion. The fluorinated cyclobutanes can be converted to a variety of cyclobutanes, cyclobutenes, and butadienes. 

Other examples of [2C+2S+1C0] cycloaddition reactions have been described by Herndon et al. by the use of chromium cyclopropyl(methoxy)carbenes. These complexes react with alkynes releasing ethene and forming cyclopenta-dienone derivatives, which evolve to cyclopentenone derivatives in the presence of chromium(O) and water [122] (Scheme 76). This reaction has been extended to intramolecular processes and also to the synthesis of some natural products [123]. These authors have also described another process involving a formal [2C+2S+1C0] cycloaddition reaction. Thus, the reaction of methyl and cyclo-propylcarbene complexes with phenylacetylene derivatives does not afford the expected benzannulated products, and several regioisomers of cyclopentenone derivatives are the only products isolated [124] (Scheme 76). 

A more detailed study of the hydration of phenylacetylene, 9a, and three substituted phenylacetylenes, p-methoxy 10, p-methyl 11, and p-chlorophenyl-acetylene 12, in aqueous sulfuric acid containing 5% ethanol has been carried out by Noyce and co-workers (19,20). The hydration obeys general acid catalysis and gives a linear Hq dependence. The slopes for the logarithm of the observed rate constants versus Ho and the activation parameters for the hydration of these phenylacetylenes are summarized in Table II. 

Phenylacetylene Benzene, ethynyl- (8, 9) (536-74-3) p-Tolylacetylene Toluene, p-ethynyl- (8) Benzene, l-ethynyl-4-methyl- (9) (766-97-2)... 

Phenylacetylene is apparently one of thee few actylenes so far reported which is able to react via the cis addition of Co—H. Methyl propiolate, ethyl... 

In 1988, Linstrumelle and Huynh used an all-palladium route to construct PAM 4 [21]. Reaction of 1,2-dibromobenzene with 2-methyl-3-butyn-2-ol in triethylamine at 60 °C afforded the monosubstituted product in 63 % yield along with 3% of the disubstituted material (Scheme 6). Alcohol 15 was then treated with aqueous sodium hydroxide and tetrakis(triphenylphosphine)palladium-copper(I) iodide catalysts under phase-transfer conditions, generating the terminal phenylacetylene in situ, which cyclotrimerized in 36% yield. Although there was no mention of the formation of higher cyclooligomers, it is likely that this reaction did produce these larger species, as is typically seen in Stephens-Castro coupling reactions [22]. 

On the basis of these results and Damiano s report [28], Darcel et al. described an iron-catalyzed hydration of terminal alkynes using catalytic amounts of iron(III) chloride (10 mol%). The reaction selectively leads to the corresponding methyl ketone derivatives (Scheme 11) [29]. Iron(II) species such as FeCl2 or Fe(OAc)2 were not able to promote the reaction, the starting phenylacetylene remained unchanged after several days at 75°C. 

In addition, the most efficient mem-ligand depicted above was successfully applied, in 2006, to the alkynylation of ketones. Thus, Liu et al. showed that this ligand was able to catalyse the enantioselective addition of phenylacetylene to various ketones, using Cu(OTf)2 as the starting base in toluene. The results were excellent and homogeneous not only for substituted aryl alkyl ketones, but also for aliphatic methyl ketones (Scheme 4.6). 

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... 

Dipolar cycloaddition reaction of trimethylstannylacetylene with nitrile oxides yielded 3-substituted 5-(trimethylstannyl)isoxazoles 221. Similar reactions of (trimethylstannyl)phenylacetylene, l-(trimethylstannyl)-l-hexyne, and bis (trimethylsilyl)acetylene give the corresponding 3,5-disubstituted 4-(trimethyl-stannyl)isoxazoles 222, almost regioselectively (379). The 1,3-dipolar cycloaddition reaction of bis(tributylstannyl)acetylene with acetonitrile oxide, followed by treatment with aqueous ammonia in ethanol in a sealed tube, gives 3-methyl-4-(tributylstannyl)isoxazole 223. The palladium catalyzed cross coupling reaction of... 

A few synthetic helical polymers are known to act as chiral selectors.7a,918d l8k i9d i9h ancj are widely used as chiral stationary phases (CSP) in gas or liquid chromatography.73,53 Recently, it has been reported that the preference of one helical sense in isotropic solution can be induced by some interaction between optically inactive polymers and chiral solvents/additives. Examples of this include poly(n-hexyl isocyanate)18d l8k and poly(phenylacetylene)s bearing functional group.19d 19h The polysilane derivatives also show chiral recognition ability in solution at room temperature. Poly(methyl-ft-pinanylsilane) includes two chiral centers per bulky hydrophobic pinanyl side group28 and... 

Poly (acetylenes) [16], There are several catalysts available for polymerization of substituted acetylenes. Whereas Ziegler-Natta catalysts are quite effective for polymerization of acetylene itself and simple alkylacetylenes, they are not active towards other substituted acetylenes, e.g. phenylacetylenes. Olefin-metathesis catalysts (Masuda, 1985 Masuda and Higashimura, 1984, 1986) and Rh(i) catalysts (Furlani et al., 1986 Tabata, 1987) are often employed. In our experience, however, many persistent radicals and typical nitrogen-containing functional groups serve as good poisons for these catalysts. Therefore, radical centres have to be introduced after construction of the polymer skeletons. Fortunately, the polymers obtained with these catalysts are often soluble in one or other organic solvent. For example, methyl p-ethynylbenzoate can be polymerized to a brick-coloured amorph- See the Appendix on p. 245 of suffixes to structural formula numbers. 

Water-soluble mthenium vinyUdene and aUenylidene complexes were also synthetized in the reaction of [ RuCl2(TPPMS)2 2] and phenylacetylene or diphenylpropargyl alcohol [29]. The mononuclear Ru-vinylidene complex [RuCl2 C=C(H)Ph)(TPPMS)2] and the dinuclear Ru-aUylidene derivative [ RuCl(p,-Cl)(C=C=CPh2)(TPPMS)2 2] both catalyzed the cross-olefin metathesis of cyclopentene with methyl acrylate to give polyunsaturated esters under mild conditions (Scheme 7.10). 

Methyl phenylethynyl telluride (typical procedure). To NaNH2 (from 6.0 g, 0.26 mol Na) in liquid NHj (250 mL) is added phenylacetylene (25 g, 0.25 mol) dropwise, and then Te powder (30 g, 0.24 mol) in small portions, stirring well for 30 min. Methyl iodide (36 g, 0.25 mol) is added over 20 min to the tellurolate solution. The NHj is then evaporated, the residue extracted with ether and the ether solntion washed with HjO and dried (MgS04). The residue is distilled under vacnum, giving the product (28 g (46%) b.p. 122-124°C/2 torr). 

A cationic rhodium complex-catalyzed codimerization of 1,3-dienes with alkynes gives the corresponding cyclohexadienes in good yields with high regioselectively, as exemplified in the reaction of 2-methyl-l,3-butadiene with phenylacetylene (Eq. 12) [31]. 

Die direkte, reduktive Aminierung einer acetylenischen Gruppe gelingt bei 2-Ethinyl-pyri-dinen durch Erhitzen mit Methylamin-Hydrochlorid und Natrium-cyanoboranat in Ethanol2. So erhalt man z. B. aus 2-Ethinyl-6-methyl-pyridin bei einer Reaktionszeit von 24 h 2-(2-Dimethylammo-ethyl)-6-methyl-pyridin in 76% Ausbeute. Mit Phenylacetylen gelingt die Reaktion nicht aus (4-Nitro-phenyl)-acetylen und Methylamin-Hydrochlorid erhalt man dagegen in glatter Reaktion l-Methylamino-2-(4-nitro-phenyl)-ethan. 

---