22524-51-2

Upstream product

• 67-56-1 methanol 
• 2604-45-7 2,3,5,6-tetramethylbenzoic acid 
• 616-38-6 carbonic acid dimethyl ester 
• 1646-53-3 bromodurene 
• 186581-53-3 diazomethane 
• 77-78-1 dimethyl sulfate 

Relevant academic research and scientific papers

Catalytic methyl transfer from dimethylcarbonate to carboxylic acids

Although methylation reactions are commonplace, currently used reagents are hazardous, toxic, and/or unstable. Dimethylcarbonate has been put forth as an inexpensive, nontoxic, and green potential methylating reagent. Herein we report a general, base-catalyzed methyl transfer from dimethylcarbonate to carboxylic acids. High selectivity for esterification is observed even in the presence of unprotected phenols, and the mild reaction conditions enable conservation of stereochemistry at epimerizable stereocenters. Isotope-labeling studies suggest a mechanism proceeding by direct methyl transfer from dimethylcarbonate to the substrate.

13C and 1H nuclear magnetic resonance of methyl-substituted acetophenones and methyl benzoates: Steric hindrance and inhibited conjugation

The 1H and 13C NMR spectra of 14 methyl-substituted acetophenones and 14 methyl-substituted methyl benzoates were assigned and interpreted with respect to the conformation of the Car - C(O) bond. The substituent effects are proportional in the two series and can be divided into polar and steric: each has different effects on the 13C SCS of the individual atoms. In the case of C atoms C(O), C(1) and CH3(CO), the steric effects were quantitatively separated by comparing SCS in the ortho and para positions. The steric effects are proportional for the individual C atoms and also to steric effects estimated from other physical quantities. However, they do not depend simply on the angle of torsion φ of the functional group as anticipated hitherto. A better description distinguishes two classes of compounds: sterically not hindered or slightly hindered planar molecules and strongly sterically hindered, markedly non-planar. In order to confirm this reasoning without empirical correlations, the J(C,C) coupling constants were measured for three acetophenone derivatives labeled with 13C in the acetyl methyl group. The constants confirm unambiguously the conformation of 2-methylacetophenone; their zero values are in accord with the conformation of 2,6-dimethylacetophenone. The zero values in the unsubstituted acetophenone are at variance with previous erroneous report but all J(C,C) values are in accord with calculations at the B3LYP/6-311++G(2d,2p)// B3LYP/6-311+G(d,p) level. Copyright

Oxidation of Aromatic Compounds. II. Oxidation of Methyl Derivatives of Benzoic Acid and Acetophenone in the System HSO3F-PbO2

Low-temperature oxidation of methyl derivatives of benzoic acid and acetophenone in the system HSO3F-PbO2 proceeds with intermediate formation of radical cations and results in replacement of hydrogen atom in methyl group or benzene ring.The reaction allows preparation of various substituted derivatives of benzyl alcohols and alkylated phthalides.

Concepts of sterically hindered resonance and buttressing effect: Gas-phase acidities of methyl-substituted benzoic acids and basicities of their methyl esters

Two classical terms "Steric Hindrance to Resonance" and "Buttressing Effect" are revisited on the basis of the gas-phase acidities of nine methyl-substituted benzole acids and of the gas-phase basicities of their methyl esters, measured using FT- ICR spectrometry. By combining these data with published heats of formation of the neutrals and by using the principle of isodesmic reactions, relative enthalpies of formation were evaluated separately for the acid molecules, their anions (deprotonated), and their protonated cations (substituted by the protonated forms of the corresponding methyl esters). Energies of all species were also calculated at the semiempirical level (AMI). Substituent effects on the gas-phase acidity are similar to those on the acidity in water. All the methyl groups have a stabilizing polar effect, and o-methyl groups have a destabilizing steric effect, both effects increasing from the deprotonated forms to the acid molecules and then to the protonated forms. Separation of the two effects was attempted, assuming equal polar effects in the ortho and para positions. The results are internally consistent: their detailed analysis is in favor of a primary steric effect rather than a steric inhibition of resonance. The latter must be relatively weaker and operating only in 2,6-dimethyl derivatives, which are certainly nonplanar. In the literature this concept has been used too broadly, even for compounds for which the nonplanar conformation has not been proven. The concept of buttressing effect has been confirmed for methyl-substituted benzoic acids, but it is formulated more generally and more exactly. According to the new definition, it can be observed even for nonadjacent substituants.