Thiophen 2,5-dimethyl

Thiophene, 2,5-dimethyl-3-lithio-ring opening, 4, 81 Thiophene, 2,5-dimethylthio-3,4-disubstituted synthesis, 4, 872 Thiophene, dinitro-... 

I.r. Spectra and Dipole Moments.—Complete sets of harmonic symmetry force constants have been developed for several heterocyclics, including thiophen. The calculations were based on observed vibrational frequencies from the literature. Calculated frequencies for [ H4]thiophen, [2,5- H2]thiophen, and [3,4- Ha]thiopheu are given. The i.r. (3650— 50cm ) and Raman spectra of 2-chloro- and 2-bromo-thiophen, 2,5-dimethyl-, 2,5-dichloro-, and 2,5-dibromo-thiophen, in the liquid state, have been interpreted. The spectroscopic thermodynamic functions have been calculated and the values for 298 K have been reported. The... 

Wild and cultivated blackberries have been used as food and medicine for hundreds of years [106]. Approximately 150 volatiles have been reported from blackberries [107]. The aroma profile is complex, as no single volatile is described as characteristic for blackberry [108, 109]. Several compounds have been suggested as prominent volatiles in blackberries using AEDA, e.g. ethyl hexanoate, ethyl 2-methylbutanoate, ethyl 2-methylpropanoate, 2-heptanone, 2-undecanone, 2-heptanol, 2-methylbutanal, 3-methylbutanal, hexanal, ( )-2-hexenal, furaneol, thiophene, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, 2-methylthiophene, methional, a-pinene, limonene, linalool, sabinene. 

The detoxification of catalysts poisoned by Group V or VI compounds can be accomplished by reactions in which these inhibitors are converted to substances that do not have unshared electron pairs. For instance, bivalent sulfur compounds can be oxidized to sulfones or sulfonic acids by treatment with hypochlorite or hydroperoxides. "2,108 Thiophene, dimethyl sulfide and other sulfur and metal ion poisons as well as phosphorous"" and arsenic compounds " can be removed from platinum by washing the catalyst with acetic acid. This method for the reactivation of the catalyst is simpler than the oxidation techniques. Acidic or basic inhibitors are removed by the addition of an appropriate amount of base or acid, respectively. The effect of a small amount of inhibitor can frequently be overcome by the use of a larger amount of catalyst. 

Chapter V. Quinaldine (V,2) 2-methyl-, 2 5-dimethyl- and 2-acetyl-thiophene (V,8-V,10) 2 5-dimethyl and 2 4-dimethyl-dicarbethoxy-p3nrole (V,12-V,13) 2-amino- and 2 4 dimethyl-thiazole (V,15-V,16) 3 5-dimethyl-pyrazole (V,17) 4-ethylp3rridine (from pyridine) (V,19) n-amyl-pyridines from picolines) (V,28) picolinic, nicotinic and isonicotinic acid (V,21-V,22) (ethyl nicotinate and p-cyanop3n idine (V,23-V,24) uramil (V,25) 4-methyl-(coumarin (V,28) 2-hyi-oxylepidine (V,29). 

Treatment of 192 with dimethyl acetylenedicarboxylate yields a thiophene derivative (195) when R = Ph and a 2-p3Tidone (1S>6) derivative when R = H (Scheme 100). The proposed mechanism involves the formation of a mesoionic derivative (193) initially further dipolar addition yields adduct 194, the decomposition of which is dependent on the R substituent as described for related compounds (435). ... 

Dimethyl sulfide [75-18-3]., thioethers, thioformaldehyde [865-36-17, and thiophene [110-02-1] are among other possible carbon disulfide hydrogenation... 

An important extension of these reactions is the Mannich reaction, in which aminomethyl-ation is achieved by the combination of formaldehyde, a secondary amine and acetic acid (Scheme 24). The intermediate immonium ion generated from formaldehyde, dimethyl-amine and acetic acid is not sufficiently reactive to aminomethylate furan, but it will form substitution products with alkylfurans. The Mannich reaction appears to be still more limited in its application to thiophene chemistry, although 2-aminomethylthiophene has been prepared by reaction of thiophene with formaldehyde and ammonium chloride. The use of A,iV-dimethyf (methylene) ammonium chloride (Me2N=CH2 CF) has been recommended for the iV,iV-dimethylaminomethylation of thiophenes (83S73). 

Benzo[Z)]thiophene reacts with dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate in a cyclo-addition-fragmentation reaction to yield (143), whereas benzo[A]furan and N- methylindole yield products (144) arising from ring opening and recyclization (76AP679). 

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). 

Benzo[6]thiophene, 1,2-dimethyl-cycloaddition reactions with dichloroethene, 4, 793 Benzo[6]thiophene, 2,3-dimethyl-nitration, 4, 763... 

Benzo[b]thiophene-2,3-dicarboxylic acid dimethyl ester synthesis, 4, 895... 

Dithiin, 2,4-dimethyl-2,4,6-triphenyl-thiophene synthesis from, 4, 903... 

Thieno[3,4-h]thiophene, 2-methoxycarbonyl-formylation, 4, 1052 Thieno[3,4-c]thiophene, 1,3-dimethyl-synthesis, 4, 1058... 

Thiophene, 3-pentadeuterophenyl-chemical shifts, 4, 730 Thiophene, 2-phenyl-oxidation, 4, 800 phototranspositions, 4, 743 rearrangement, 4, 42 reduction, 4, 775 synthesis, 4, 865, 914 UV spectrum, 4, 735 Thiophene, 3-phenyl-photochemical rearrangements, 4, 735 phototranspositions, 4, 743 lsmeier formylation, 4, 759 Thiophene, 2-pivaloyl-Birch reduction, 4, 775 Thiophene, polybromo-reactivity, 4, 829 Thiophene, polylithio-synthesis, 4, 831 Thiophene, (propargylthio)-rearrangement, 4, 746 Thiophene, 2-(3-pyridinyl)-synthesis, 4, 781 Thiophene, 2-(5-pyrimidinyl)-synthesis, 4, 781 Thiophene, 3-pyrrolidinyl-cycloaddition reactions, 4, 68 with dimethyl acetylenedicarboxylate, 4, 788-789... 

Thiophene-3-carboxylic acid, 2-amino-4,5-dimethyl-protonation, 4, 811... 

It now seems definitely proved that the thiothiophthene (86) rearranged reversibly to a thiophene (87) under the influence of alkali and not to a thiepin derivative, The dimethyl ether of (87) has been oxidized to 4-methylsulfonyl-2-thiophenecarboxylic acid (88)... 

The condensation of thiophene with ketones, under the influence of 70% H2SO4, leads to di-2-thienylmethane derivatives. With acetone, 2,2-di-(2-thienyl) propane (97) is obtained. The condensation of thiophene with dimethyl phenyl carbinol, methyl diphenyl carbinol, and f-butylalcohol, in the presence of SnCU gave (98), (99), and 2,5-di-f-butylthiophene, respectively. Triphenyl carbinol does not... 

Additional examples of the reactivity of the 4-position in thiophenes with —I-j-M-substituent in the 3-position are provided by the bromination of 3-thiophenecarboxylic acid to 2,4,5-tribromothio-phenecarboxylic acid and the recent diacetylation of 2,5-dimethyl-thiophene by Goldfarb et who used the swamping catalyst... 

The chloromethylation of 2,6-dimethyl- and 2,5-diethyl-thiophene both with chlorodimethyl ether and formaldehyde and hydrochloric acid gives a mixture of mono- and di-chloromethylated product. " The former reagent gives the larger proportion of monochloromethyl-ated product. " If the chloromethylation is carried out in the presence of zinc chloride, (120) and (121) are obtained. ... 

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