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Carlo Punta

Publications and source records attributed to Carlo Punta.

5 recordsLinked to original sources
PubMed2006

Peroxyl radical clocks.

A series of peroxyl radical clocks has been developed and calibrated based on the competition between the unimolecular beta-fragmentation (k(beta)) of a peroxyl radical and its bimolecular reaction with a hydrogen atom donor (k(H)). These clocks are based on either methyl linoleate or allylbenzene and were calibrated directly with alpha-tocopherol or methyl linoleate, which have well-established rate constants for reaction with peroxyl radicals (k(H-tocopherol) = 3.5 x 10(6) M(-1) s(-1), k(H-linoleate) = 62 M(-1) s(-1)). This peroxyl radical clock methodology has been successfully applied to determine inhibition and propagation rate constants ranging from 10(0) to 10(7) M(-1) s(-1).

Calibration↗
PubMed2006

Free-radical version of the strecker synthesis of alpha-aminoamides promoted by aqueous H2O2/TiCl3/HCONH2 system.

A new reaction of general synthetic interest representing the free-radical version of the Strecker synthesis to alpha-aminoamides is reported. A hydroxy radical, generated by Ti(III) one-electron reduction of H2O2, abstracts a H atom from the C-H bond of formamide, and the resulting carbamoyl radical adds to the C atom of aldimines formed in situ, leading to a one-pot synthesis of alpha-aminoamides. Several types of aldehydes can participate in this process.

Journal Article↗
PubMed2005

Peroxidation of polyunsaturated fatty acid methyl esters catalyzed by N-methyl benzohydroxamic acid: a new and convenient method for selective synthesis of hydroperoxides and alcohols.

A new catalytic system, based on N-methyl benzohydroxamic acid (NMBHA), was developed for the selective synthesis of lipid hydroperoxides and alcohols by aerobic oxidation of lipid precursors. The reactions were carried out under mild conditions with air at atmospheric pressure and 37 degrees C. The products were isolated in much better yields (50-60%) as compared to previously reported procedures. NMBHA can be recovered at the end of the reaction and recycled. The putative reactive intermediate, a nitroxyl radical, readily abstracts a hydrogen atom from polyunsaturated lipid precursors such as linoleate esters, and NMBHA itself is an excellent hydrogen atom donor, thus conferring high selectivity to oxidations catalyzed by this reagent.

Alcohols↗
PubMed2002

Aerobic oxidation of N-alkylamides catalyzed by N-hydroxyphthalimide under mild conditions. Polar and enthalpic effects.

The oxidation of N-alkylamides by O(2), catalyzed by N-hydroxyphthalimide (NHPI) and Co(II) salt, leads under mild conditions to carbonyl derivatives (aldehydes, ketones, carboxylic acids, imides) whose distribution depends on the nature of the alkyl group and on the reaction conditions. Primary N-benzylamides lead to imides and aromatic aldehydes at room temperature without any appreciable amount of carboxylic acids, while under the same conditions nonbenzylic derivatives give carboxylic acids and imides with no trace of aldehydes, even at very low conversion. These results are explained through hydrogen abstraction by the phthalimide-N-oxyl (PINO) radical, whose reactivity with benzyl derivatives is governed by polar effects, so that benzylamides are much more reactive than the corresponding aldehydes. The enthalpic effect is, however, dominant with nonbenzylic amides, making the corresponding aldehydes much more reactive than the starting amides. The importance of the bond dissociation energy (BDE) of the O-H bond in NHPI is emphasized.

Journal Article↗