Acetonitrile mesityl

The reaction mixture is allowed to cool to about 40° (Note 7) and extracted with three 300-ml. portions of benzene. The benzene solution is washed well with water, dried over calcium chloride, filtered, and distilled under slightly reduced pressure to remove all the benzene. The residue is then distilled in vacuo from a Claisen flask with a wide-bore side arm. The yield of mesityl acetonitrile boiling at 160-165°/22 mm. is 128-133 g. (89-93%) (Note 8). This product is sufficiently pure for the next step. When recrystallized from petroleum ether, it melts at 79-80°. 

C. Mesitylacetic acid. To 900 ml. of water in a 3-1. threenecked flask is added 750 ml. of concentrated sulfuric acid.When the mixture has cooled to about 50°, 127 g. (0.80 mole) of mesityl-acetonitrile is added (Note 9), and the mixture is refluxed and stirred mechanically for 6 hours. At the end of this period, a large amount of mesitylacetic acid has precipitated from the solution. The contents of the flask are cooled and poured into 3 1. of ice water. The acid is collected on a Buchner funnel and washed well with water. A solution of the acid in dilute alkali is boiled with Norite, and the acid is precipitated from the filtered solution by acidifying with dilute hydrochloric acid. The mesitylacetic acid is collected on a filter, washed well with water, and dried in an oven at about 80°. The yield of mesitylacetic acid melting at 163-166° is 123 g. (87%). After recrystallization from dilute alcohol or ligroin, the acid melts at 167-168°. 

Several possibilities for a large-scale synthesis of mesitylacetic acid 12, a central building block in the synthesis of spiromesifen 8a, were examined (Scheme 28.4.2). Using the classical standard route, mesitylene 13 is transferred into mesityl acetonitrile 14 via chloromethylation and cyanide exchange, which is then saponified to the aryl acetic acid. Another route examined is the Friedel-Crafts alkylation of mesitylene with 1,3-dichloro-propene to the adduct 15, which is ozo-nolyzed to the corresponding aldehyde in the form of its dimethyl acetal and than further oxidized with hydrogen peroxide under acidic conditions to mesityl acetic... 

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

Sterically hindered, mesityl-substituted, stable enols 72 have been examined with regard to one-electron oxidation. Using two equivalents of a one-electron oxidant such as triarylaminium salts, iron(III)phenanthroline, thianthrenium perchlorate or ceric ammonium nitrate in acetonitrile-benzofurans 73 are obtained in good yields within a few seconds [111]. 

Two possible mechanisms are proposed. Primarily the enol radical cation is formed. It either undergoes deprotonation because of its intrinsic acidity, producing an a-carbonyl radical, which is oxidized in a further one-electron oxidation step to an a-carbonyl cation. Cyclization leads to an intermediate cyclo-hexadienyl cation. On the other hand, cyclization of the enol radical cation can be faster than deprotonation, producing a distonic radical cation, which, after proton loss and second one-electron oxidation, leads to the same cyclo-hexadienyl cation intermediate as in the first reaction pathway. After a 1,2-methyl shift and further deprotonation, the benzofuran is obtained. Since the oxidation potentials of the enols are about 0.3-0.5 V higher than those of the corresponding a-carbonyl radicals, the author prefers the first reaction pathway via a-carbonyl cations [112]. Under the same reaction conditions, the oxidation of 2-mesityl-2-phenylethenol 74 does not lead to benzofuran but to oxazole 75 in yields of up to 85 %. The oxazole 75 is generated by nucleophilic attack of acetonitrile on the a-carbonyl cation or the proceeding enol radical cation. 

A novel tricyclic mesoionic tetrazolium derivative of 1,3,5-triazocine 9 was the major product of photochemical conversion of 5-azido-l-mesityl-3-phenyltetrazolium tetrafluoroborate 32 (Scheme 4, Section 14.08.5.2.1 <2000JHC1129>). The proposed mechanism of the transformation included benzylic hydrogen abstraction by the triplet nitrene intermediate to produce biradical species, which captures the solvent acetonitrile to afford 9. 

The reaction of ci5-[PtCl2(SEt2)2] with mesityl-lithium produced the trans-isomer of [PtCl(mesityl)(PEt3)2]. The isomerization was accelerated by mesityl-lithium in solution. [PtCl3(am)] and acetonitrile produced m-[PtCl2(am)-(NCMe)] (am is iso-propylamine or tert-butylamine). " In MeCN or acetone solution only the i50-propylamine complex underwent isomerization. Since a solvent-initiated consecutive displacement is the most probable mechanism, steric hindrance may play a role. 

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