Phenylacetylene ester

J-unsaturated ester is formed from a terminal alkyne by the reaction of alkyl formate and oxalate. The linear a, /J-unsaturated ester 5 is obtained from the terminal alkyne using dppb as a ligand by the reaction of alkyl formate under CO pressure. On the other hand, a branehed ester, t-butyl atropate (6), is obtained exclusively by the carbonylation of phenylacetylene in t-BuOH even by using dppb[10]. Reaction of alkynes and oxalate under CO pressure also gives linear a, /J-unsaturated esters 7 and dialkynes. The use of dppb is essen-tial[l 1]. Carbonylation of 1-octyne in the presence of oxalic acid or formic acid using PhiP-dppb (2 I) and Pd on carbon affords the branched q, /J-unsatu-rated acid 8 as the main product. Formic acid is regarded as a source of H and OH in the carboxylic acids[l2]. 

To be eligible to living anionic polymerization a vinylic monomer should carry an electron attracting substituent to induce polarization of the unsaturation. But it should contain neither acidic hydrogen, nor strongly electrophilic function which could induce deactivation or side reactions. Typical examples of such monomers are p-aminostyrene, acrylic esters, chloroprene, hydroxyethyl methacrylate (HEMA), phenylacetylene, and many others. 

Cyclization of substituted phenylacetylene sequences afforded functionalized macrocycles that were amenable to subsequent manipulation. For example, transesterification of 42 with octanol in the presence of 18-crown-6 ether and potassium carbonate gave the corresponding ester in 85% yield (Scheme 13). The ester functionalities could be reduced by DIBALH to give the hydroxymethyl-substituted macrocycle (43) in 61 % yield. The low yield of this particular transformation is attributed to mechanical losses during purification, due to the highly polar nature of the product. Macrocycle 43 could then be treated with alkyl bromides to give a group of benzyl ether derivatized PAMs. 

Cycloaddition of 2-cyanoalk-2-enones with several conjugated dienes proceeded under zinc chloride catalysis.636 Zinc halides have also shown reactivity with phenylacetylenes.637 Zinc chloride is an effective Lewis acid catalyst in the Diels Alder reactions of the keto esters and the effects on stereochemistry of catalysts used have been examined.638... 

First, 4-chloropyrimidine 86 was treated with phenylacetylene to give alkynylpyrimidine 87 [62], The fact that the Sonogashira reaction proceeded readily at room temperature may be ascribed to the electron-withdrawing effect of the neighboring ethoxycarbonyl group on 86. When heated with ammonia in EtOH, alkynylpyrimidine ester 87 cyclized efficiently to produce pyridyl lactam 88. 

As exemplified in Eq. 8.38, thermal [2 + 2] cycloadditions of 4-vinylidene-2-oxazoli-dinone 287 and alkynes such as phenylacetylene result in the formation of 3-phenyl-substituted methylenecyclobutene 288 [149]. The authors confirmed by NMR analysis that only the Z-configuration isomer was formed. It is worth noting that the [2 + 2] cycloaddition of allenes 287 is not restricted to alkynes even olefins such as acrylic esters or silyl enol ethers furnish the corresponding methylenecyclobutanes... 

Octakis(trifluorophosphine)dirhodium, Acetylenic esters, 4387 Phenylacetylene, 2912... 

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). 

Naphthalene, CgoHg Anthracene, C,4H,o Phenanthrene, C,4H,o Biphenyl, C,2H,o Cyclopentadiene, CsH Styrene, CgHjCHCHj Phenylacetylene, CgHjCCH Phenol, C4H5OH Aniline, QH5NH2 Pyridine, C5NH5 Acids, RCOOH Esters, RCOOR ... 

Yashima et al. showed an example where the polymer helicity was controlled by enzymatic enantioselective acylation of the monomers [109]. Optically active phenylacetylenes containing hydroxyl or ester groups were obtained by the kinetic resolution of the corresponding racemic hydroxy-functional phenylacetylene (see Scheme 16). Polymerization of the phenylacetylenes afforded an optically active poly(phenylacetylene) with a high molecular weight (Mn = 89kDa PDI = 2.0) and... 

Unlike W and Mo catalysts, Rh catalysts are not suited to oriho-swhstxtutcd phenylacetylenes because Rh catalysts are rather sensitive to the steric effect. Instead, Rh catalysts are suitable to various phenylacetylenes having polar groups (e.g., ether, ester, amine, carbazole, imine, nitrile, azobenzene, nitro groups) at ra-position, resulting in the formation of high MW poly(phenylacetylenes). Many such examples are found in Table 3. 

Rh complexes are examples of the most effective catalysts for the polymerization of monosubstituted acetylenes, whose mechanism is proposed as insertion type. Since Rh catalysts and their active species for polymerization have tolerance toward polar functional groups, they can widely be applied to the polymerization of both non-polar and polar monomers such as phenylacetylenes, propiolic acid esters, A-propargyl amides, and other acetylenic compounds involving amino, hydroxy, azo, radical groups (see Table 3). It should be noted that, in the case of phenylacetylene as monomer, Rh catalysts generally achieve quantitative yield of the polymer and almost perfect stereoregularity of the polymer main chain (m-transoidal). Some of Rh catalysts can achieve living polymerization of certain acetylenic monomers. The only one defect of Rh catalysts is that they are usually inapplicable to the polymerization of disubstituted acetylenes. Only one exception has been reported which is described below. 

Catalytic systems to afford linear esters selectively are scant.306,309 A report in 1995 disclosed that palladium complexes based on l,l -bis(diphenylphosphine)fer-rocene showed excellent regioselectivity for the formation of linear a,p-unsaturated esters.309 The results with phenylacetylene are remarkable because this compound is known to exhibit a distinct preference for the formation of the branched products on palladium-catalyzed carboxylations. Mechanistic studies indicate that the alkoxycarbonylation of alkynes proceeds via the protonation of a Pd(0)-alkyne species to give a Pd-vinyl complex, followed by CO insertion and alcoholysis.310... 

Ollis, and Ramsden520 treated 99, 100 and 101 with neat EPP and obtained the pyrazole 103 and the phenylpropiolic ester dimer 104, but no 105. A comparative study was carried out with phenylacetylene. When 100 was heated with DM AD in dioxane, 25% of the pyrazole 106 was obtained. These authors have concluded that the cycloaddition of alkynes to isosydnones is analogous to that of sydnones but the reactions are slower and the cycloadducts are obtained in lower yields. 

Although, at that time, the term supramolecular chemistry had not yet been coined, the practical potential for inclusion complexation for acetylene alcohol guests 1 and 2 was recognized back in 1968 [12], Spectroscopic studies showed that 1 and 2 formed molecular complexes with numerous hydrogen-bond donors and acceptors, i.e. ketones, aldehydes, esters, ethers, amides, amines nitriles, sulfoxides and sulfides. Additionally, 1 formed 1 1 complexes with several n-donors, such as derivatives of cyclohexene, phenylacetylene, benzene, toluene, etc. The complexation process investigated by IR spectrometry revealed the presence of OH absorption bands at lower frequencies than those for uncomplexed 1 and 2 [12], These data, followed by X-ray studies, confirmed that the formation of intermolecular hydrogen bonds is the driving force for the creation of complexes [13],... 

A-Methyl-/V-nitroso-a-(trimethylsilyl)benzylamine reacts thermally with DMAD to give 3,4-dicarbomethoxy-l-methyl-lH-pyrazole. The reaction is highly sensitive to the temperature upon increasing the temperature from 25 to 110 °C, the reaction time drops from 168 h to 3 min and yields increase from 30 to 100%. No reaction occurs from non-silylated /V-methyl-/V-nitrosobenzylamine. Other acetylenic esters have been successfully tested. In contrast, phenylacetylene gives a poor yield of the adduct and diphenylace-tylene does not react.473... 

The diphosphine of choice for obtaining good regioselectivity is the bis(diphe-nylphosphino)butane (Scheme 4). It enables addition of a variety of carboxylic acids to phenylacetylene and hexyne. The reaction temperature, which enables complete conversion can be reduced from 80 to 0 °C when the acidity of the carboxylic acid increases in the pK, range from 5 to 1.5. The milder temperature conditions always lead to higher regioselectivity of the addition. The preparation of functionalized (Z)-cnol esters can be conducted in apolar solvents such as toluene or pentane dienyl esters are selectively produced from conjugated enynes [9]. 

Sasson and Webster119 reported some examples of monoprotic carbon acids, for example alkylmalonic esters and phenylacetylene, that are directly halogenated in high yield by polyhalo alkanes under mild conditions when catalyzed by tetrabutylammonium fluoride (TBAF) (equation 76). They do not discuss the halogenation mechanism other than to say that the reaction is apparently taking place via nucleophilic attack on the tetra-halomethane (equation 77). It is reasonable to believe that it is the carbanion of the sub-... 

Recently, it was shown that the metathesis catalyst RuCl2(PCy3)2(=CHPh), where Cy is cyclohexyl, reacted in refluxing toluene with phenylacetylene to produce a ruthenium vinylidene species which promoted the regioselective dimerization of phenylacetylene into ( )-1,4-diphenylbutenyne [56]. The addition of 1 Eq acetic acid did not lead to enol esters but to a faster reaction and the stereoselective dimerization of phenylacetylene into the Z dimer. 

---