Phenylacetylene preparation

Over the past decade, literally dozens of new AB2-type monomers have been reported leading to an enormously diverse array of hyperbranched structures. Some general types include poly(phenylenes) obtained by Suzuki-coupling [54, 55], poly(phenylacetylenes prepared by Heck-reaction [58], polycarbosilanes, polycarbosiloxanes [59], and polysiloxysilanes by hydrosilylation [60], poly(ether ketones) by nucleophilic aromatic substitution [61] and polyesters [62] or polyethers by polycondensations [63] or by ring opening [64]. 

Stereospecific polymerization catalysts. The poly(phenylacetylene) prepared with Ziegler catalyst 28 possesses mainly the cis-cisoidal structure (as evidenced by the C—H out-of-plane deformation at 740 cm" in the IR spectrum), and is insoluble in all solvents owing to its high crystallinity. Rhodium catalysts such as 29 and 30 provide a soluble, cis-transoidal poly(phenylacetylene) . This polymer exhibits a sharp peak due to the olefinic proton at b 5.8 in the NMR spectrum. 

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Phenylacetylene is readily prepared by the dehydrohalogenatlon of styrene dibromide with a solution of sodamide in liquid ammonia ... 

Many examples of insertions of internal alkynes are known. Internal alkynes react with aryl halides in the presence of formate to afford the trisubstituted alkenes[271,272]. In the reaction of the terminal alkyne 388 with two molecules of iodobenzene. the first step is the formation of the phenylacetylene 389. Then the internal alkyne bond, thus produced, inserts into the phenyl-Pd bond to give 390. Finally, hydrogenolysis with formic acid yields the trisubstituted alkene 391(273,274], This sequence of reactions is a good preparative method for trisubstituted alkenes from terminal alkynes. 

Solutions of RC triple-bond C—Ti(0-/-C2H2)2 can be prepared by treating acetylenic compounds, such as phenylacetylene, with butyl lithium and then Cl—Ti(0-/-C2H2)2. These materials can react with aldehydes and epoxides to give the expected addition products (215). 

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. 

Pyrazinone bearing a phenylalkynyl substituent at position C-3, was prepared in 47% yield via Sonogashira reaction with 7 equiv of phenylacetylene in a mixture of toluene/triethylamine (2 1) using Pd[P(Ph3)2]Cl2 and Cul as the catalyst system (Scheme 37). 

It is noteworthy that photoluminescent poly(vinylene-arsine)s have also been prepared by radical copolymerisation of phenylacetylene and an arsenic atomic biradical equivalent [71]. 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

A very interesting feature of the above system is that the reactions can be conducted under air, without solvent. Preparative scale (40 g) hydroamination of phenylacetylene with PhNHj yielded the acetophenone N-phenylimine in 92% isolated yield in 3 h (TOF = 100 h ). 

A mixture of phenylacetylene and the pure ( anhydrous) acid prepared at — 180°C exploded when allowed to warm to — 78° C, possibly owing to formation of unstable 1-phenylethenyl perchlorate [1]. Reaction of various phenylacetylenes in acetic acid at 40° C is controllable [2],... 

In addition to the ionic liquid-mediated procedure in solution (see Scheme 6.112), Leadbeater and coworkers also presented a solid-phase protocol for a one-pot Mannich reaction employing the above mentioned chlorotrityl linker [67]. In this approach, p-chlorobenzaldehyde and phenylacetylene were condensed with readily prepared immobilized piperazines (Scheme 7.56). 

Dichloroacetophenone has been prepared by chlorination of acetophenone with and without aluminum chloride 1 by action of dichloroacetyl chloride upon benzene and aluminum chloride 1 by action of hypochlorous acid upon phenylacetylene 2 by heating trichloromethylphenylcarbinol 3 and by chlorination of phenylacetylene in alcohol.4... 

The hydrogermylation of phenylacetylene has been shown to proceed with retention at germanium12. Addition of the germyl hydride 5-3 in the presence of a Pt or Rh catalyst led to the adduct 5-23 as the major product. The enantiomer 5-23 was prepared by addition of tran.s-/3-styryllithium to chlorogermane 5 -7 prepared as shown in Scheme 10. The isopropyl analogues of 5-23 and 5-23 were similarly prepared from hydride 5-612. 

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