Acetylenes aromatic

Phenylpropiolic acid. This is an example of an aromatic acetylenic acid, and is made by adding bromine to the ethylenio linkage in ethyl cinnamate, and treating the resulting dibromide with alcohobc potassium hydroxide which eliminates two molecules of hydrogen bromide ... 

Both aliphatic and aromatic terminal alkynes reacted with aliphatic aldehydes giving exclusively a mixture of ( ,Z)-1,5-dihalo-1,4-dienes and disubstituted ( )-a,p-unsaturated ketones, the former being the major products in all cases. When nonterminal aromatic acetylenes were used, the trisubstituted ( )-a,p-unsat-urated ketones were the exclusive compounds obtained. The procedure was not valid for ahphatic and unsaturated alkymes. However, the catalytic system was found to be compatible with alcohols and their corresponding acetates although limited yields were obtained. 

The selenotelluration of acetylenes works well in the case of aromatic acetylenes, whereas aliphatic acetylenes provide a mixture of the expected selenoteUmo adducts and the diselenation product. 

Triple bonds in side chains of aromatics can be reduced to double bonds or completely saturated. The outcome of such reductions depends on the structure of the acetylene and on the method of reduction. If the triple bond is not conjugated with the benzene ring it can be handled in the same way as in aliphatic acetylenes. In addition, electrochemical reduction in a solution of lithium chloride in methylamine has been used for partial reduction to alkenes trans isomers, where applicable) in 40-51% yields (with 2,5-dihydroaromatic alkenes as by-products) [379]. Aromatic acetylenes with triple bonds conjugated with benzene rings can be hydrogenated over Raney nickel to cis olefins [356], or to alkyl aromatics over rhenium sulfide catalyst [54]. Electroreduction in methylamine containing lithium chloride gives 80% yields of alkyl aromatics [379]. 

Remarkable enhancements of the unimolecular c-t isomerization of c-S with p-MeO and oxidation of S with -MeO are explained by charge-spin separation in such S Unimolecular c-t isomerization of such c-S proceeds with a chain mechanism, while regioselective oxidation occurs in such S because of the spin localization. Cycloreversion of t,c,t-TPCB occurs to give a a-St 2, while the photochemical cycloreversion of TPCB and t,t,t-TPCB gives Tr-St 2 and t-St /t-St pair, respectively. Radical cations of phosphorus compounds (9 and 10 form intramolecular rr-dimer between two Nps from which Np 2 forms. Formation of intermolecular a-dimer of aromatic acetylene (11 - and 12 -) and intramolecular dimer of 13 and diarylmethanoT was observed, and the n = 3 rule is not effective for intramolecular dimer -. 

Aromatic acetylenes 22 bearing an alkyl substituent on the phenyl ring are also applicable to the silylformylation without any problem (Equation (5)). 6-Methoxy-2-naphthylacetylene 24 gives an excellent yield of the corresponding silylformylation product (Equation (6)). ... 

Thiophene is a sulphur-containing five-membered unsaturated heterocycle. The lone pair electrons of the sulphur are in the 35 orbital, and are less able to interact with the tt electrons of the double bonds. Therefore, thiophene is considered weakly aromatic. Acetylenic thiophene is found in some higher plant species. However, the thiophene ring is present in many important pharmaceutical products. 

Of all the thermosetting imide oligomers discussed in this article, the totally aromatic acetylene terminated imides are the most promising because their... 

Arene)tricarbonylchromiums in cycloadditions, 5, 243 in higher-order cycloadditions, 5, 244 in silsesquioxanes, 5, 252 Aromatic acetylenes, silylformylation, 11, 477 Aromatic aldehydes, diastereoselective coupling reactions, 11,44... 

Substitution at certain unsaturated centers has little direct stereochemical interest, because there is no choice, e.g. substitution at aromatic, acetylenic, and carbonyl carbons must go with retention. On the other hand, stereoselection is possible at ethylenic and allenic carbon, phosphorus (P—O, P=S) and sulfur (S=0) centers. There appear to be important mechanistic differences between substitutions at unsaturated carbon and phosphorus or sulfur. All SE, SH, SN substitutions at such carbon atoms appear to proceed in at least two steps, while those at phosphorus and sulfur may go in one or more steps. For the SN process, comparative data are available here, substitution at unsaturated carbon proceeds with retention, while at phosphorus and sulfur inversion predominates. Substitution at unsaturated phosphorus and sulfur sites was sufficiently similar to other saturated centers that it was considered with them. Because of these mechanistic differences, we shall examine substitutions at unsaturated carbon more closely. 

In the majority of cases alkyl hydrazines give single pyrazoles.160, 328, 336,337 In 1958 Bertrand established that allenic ketones give pyrazoles quantitatively with hydrazine.338 The reaction may be formulated as follows, the second stage being stabilization by aromatization. Acetylenic nitriles give aminopyrazoles with hydrazine.339... 

An interesting four-component radical cascade that leads to formation of 3-arylthio-substituted acrylamides 172 and involves thiyl radicals, aromatic acetylenes, and... 

The literature of the commercial development of hydrocarbons derivable from petroleum and natural gas is meager until about 1935. Since 1945, the literature has become extensive. This study includes the paraffins, olefins, alicyclics, aromatics, acetylene, and separation processes. Journals and sections of journals of value are discussed. The main subject heads to be consulted in Chemical Abstracts are given. There is considerable overlapping of subject matter in the U. S. patent classification system pertinent classes are listed. References in the bibliography were selected to show the various types available. 

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