29344-95-4Relevant academic research and scientific papers
A convenient synthesis of tri- and tetramethylbenzaldehydes from readily available phenols
Dhankher, Persis,Sheppard, Tom D.
supporting information, p. 381 - 384 (2014/03/21)
This letter describes a convenient synthesis of the six isomeric tri- and tetramethylbenzaldehydes, which are not readily available from major chemical suppliers. Formylation of readily available phenols via electrophilic aromatic substitution provides compounds containing the correct aromatic substitution pattern. ?Suzuki cross-coupling of the corresponding trifluoromethanesulfonates with methylboronic acid then provides the benzaldehydes as single isomers. Georg Thieme Verlag Stuttgart. New York.
Cycloaddition of thiophene S-oxides to allenes, alkynes and to benzyne
Thiemann, Thies,Fujii, Hideki,Ohira, Daisuke,Arima, Kazuya,Li, Yuanqiang,Mataka, Shuntaro
, p. 1377 - 1384 (2007/10/03)
Thiophenes have been treated with alkynes in the presence of m-chloroperoxybenzoic acid to give substituted arenes as cycloadducts. Alternatively, thiophene S-oxides have been prepared by oxidation from thiophenes and have been subjected to cycloaddition with alkynes in a subsequent step. The outcome of the reaction is dependent on the steric demand of the thiophene S-oxide. Some thiophene S-oxides can be reacted at temperatures as high as 140°C without decomposition. Thiophenes as deoxygenated products are the main by-products. Reactions of thiophene S-oxides with allenes give in part thiabicyclo[2.2.1]heptene S-oxides of type 12a and 13 along with aromatized products. Thiophene S-oxides also cycloadd to benzyne.
Photochemical nitration by tetranitromethane. Part XXXIV. The photochemical reactions of pentamethylbenzene and hexamethylbenzene with tetranitromethane. The formation and rearrangement of labile adducts from pentamethylbenzene
Eberson, Lennart,Hartshorn, Michael P.,Timmerman-Vaughan, David J.
, p. 1121 - 1136 (2007/10/03)
The photolysis of the charge transfer (CT) complex of tetranitromethane and Pentamethylbenzene (13) in dichloromethane at - 50 or - 78°C gives the labile epimeric 1,2,3,4,6-pentamethyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 18 and 19. Adduct 18 rearranges rapidly in [2H2]dichloromethane at 22°C (half-life 9 min) to give 2,3,4,5-tetrarnethyl-1-(2′,2′,2′-trinitroethyl)benzene (21), 2,3,4,5-tetramethylphenylnitromethane (26), 2,3,4,5-tetramethylbenzyl nitrate (32) and 2,3,4,5-tetramethylbenzyl nitrite (36). The photolysis of the tetranitromethane-13 CT complex in dichloromethane at 20°C gives compounds 21, 26, 32 and 36, in addition to their 2,3,4,6-tetramethyl analogues 20, 25, 31 and 35, the latter set of products probably arising from the rearrangement of the highly labile epimeric 1,2,3,5,6-pentamethyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 54. The photolysis of the tetranitromethane-13 CT complex in acetonitrile gives mainly the phenylnitromethane 26, while similar reaction in 1,1,1,3,3,3-hexafluoropropan-2-ol yields pentamethylnitrobenzene 24, the latter by a nitrosation/oxidation sequence. Reaction of 13 with nitrogen dioxide in dichloromethane gives mainly compounds 26 and 30. No adducts were detected in the photolysis of the CT complex of hexamethylbenzene 14 in dichloromethane at accessible reaction temperatures (≥ -20°C), but products of side-chain modification 37-46 were formed. In acetonitrile similar reaction gave in addition to the above products 37-46 the N-nitrosoacetamide 47 and its precursor 49. Compounds 47 and 49 are also formed, along with the major products pentamethylbenzyl nitrate 39 and the mono- and di-nitromethyl compounds 40 and 43, on reaction of 14 with nitrogen dioxide in acetonitrile. EPR spectroscopic examination of the photolysis of acidic (trifluoroacetic acid, 0.4 mol dm-3) solutions of tetranitromethane and 13 or 14 demonstrated the formation of the corresponding radical cation or a transformation product thereof, i.e. the 1,2,3,4,5,6,7,8-octamethylanthracene radical cation from 13 or 14·+ from 14. Acta Chemica Scandinavica 1996.
Dual Reactivity of the Formyl Cation as an Electrophile and a Broensted Acid in Superacids
Tanaka, Mutsuo,Fujiwara, Masahiro,Ando, Hisanori
, p. 3846 - 3850 (2007/10/02)
The nature of the formyl cation in the Gattermann-Koch formylation was studied by comparing the formylation with the acetylation and sulfonation in CF3SO3H-SbF5 and FSO3H-SbF5, respectively.The results of the kinetic studies in CF3SO3H-SbF5 showed that the formyl cation has dual reactivity as an electrophile and as a Broensted acid.Upon comparing the formylation with the sulfonation in FSO3H-SbF5, it was found that the protonated aromatic compounds also act as Broensted acids to produce formyl cations.Therefore, the formylation has a priority over other typical electrophilic substitutions under conditions where most of aromatic compounds are protonated because the formyl cation is reproduced close to the aromatic compounds by the protonation of CO with not only superacids but also protonated aromatic compounds.
Direct Observation of the Kinetic Acidities of Transient Aromatic Cation Radicals. The Mechanism of Electrophilic Side-Chain Nitration of the Methylbenzenes
Masnovi, J. M.,Sankararaman, S.,Kochi, J. K.
, p. 2263 - 2276 (2007/10/02)
The transient cation radicals ArCH3(.+) are spontaneously generated by the 532-nm excitation of the charge-transfer complexes with a 10-ns laser pulse.The decay kinetics of the spectral transients in the presence of added base establish the kinetic acidities (kH) for various methylarene cation radicals with different pyridines and trinitromethide.Such a proton transfer from ArCH3(.+) proceeds with a deuterium kinetic isotope effect of kH/kD ca. 3.Side-chain nitration of hexamethylbenzene (HMB) is shown to proceed in high yields via the intimate triad of reactive fragments II, , that is produced upon the charge-transfer excitation.The subsequent annihilation of the reactive triad II occurs via a rapid succession of bimolecular steps involving either (i) the initial ion-pair collapse of by proton transfer, as shown in Scheme VI, or (ii) the alternative sequence with the initial ion-radical collapse of by homolytic coupling, as shown in Scheme VII.The marked variations of kH/kD with solvent polarity and added innocuous salt (Bu4N(+)ClO4(-)), as reflected in ion-pair separation and the "special" salt effect, serve to effectively distinguish these pathways.The direct bearing of Schemes VI and VII on the mechanism of the thermal (adiabatic) nitration of methylarene side chains with nitric acid is delineated.
An Unexpected γ-Hydrogen Rearrangement in the Mass Spectra of Di-ortho-substituted Alkylbenzenes
Kingston, Eric E.,Eichholzer, John V.,Lyndon, Paul,MacLeod, John K.,Summons, Roger E.
, p. 42 - 47 (2007/10/02)
In contradiction of long-accepted mass spectrometric dogma, the site-specific γ-hydrogen rearrangement is observed in alkylbenzenes in which both ortho positions are blocked with methyl substituents.Mass spectrometric studies of a series of five trimethyl- and three tetramethylisopentylbenzenes have shown that this rearrangement is only suppressed to a significant degree in those compounds in which all three positions ortho and para to the isopenyl group are blocked.Deuterium labelling has confirmed the γ-site-specific origin of the migrating H atom while metastable studies have been used to investigate the mechanism of the rearrangement process.
TWISTED 9,10-PHENANTHRENEQUINONES: CHROMATOGRAPHIC ENRICHMENT OF ENANTIOMERS AND BARRIERS TO RACEMIZATION
Mannschreck, Albrecht,Hartmann, Erwin,Buchner, Hans,Andert, Doris
, p. 3479 - 3482 (2007/10/02)
The enantiomers (M) and (P) of helical 9,10-phenanthrenequinones were enriched by liquid chromatography with enantiomeric purities of 0.31 to 0,95.Their barriers to racemization (Table 2) were compared with the ones of the corresponding hydrocarbons.
