Kevin T. Chapman

Bio: Kevin T. Chapman is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Alcohol oxidation & Dehydrogenation. The author has an hindex of 2, co-authored 2 publications receiving 252 citations.

Convenient and inexpensive procedure for oxidation of secondary alcohols to ketones

Abstract: ether became symnietrical in the presence of 5 equiv of 18-crown-6. Comparison of the chemical shift data for the anions of 1 and 2 in the absence and presence of 5 equiv of 18crown-6 reveals a change of 257 Hz for 1 and 144 Hz for 2. The smaller chemical shift change observed for 2 is again consistent with a lesser degree of ion pairing when the counterion is hexafluorophosphate. Central to this argument is the formulation of the crown ether-diazonium salt complex 5 as resulting from insertion of the neck of the arenediazonium cation into a crown ether ~ o l l a r . ~ J ~ J ~ PrevioiJs evidence for this arrangement includes steric effects of substituents in sol~bilization~~'~ and titration cal~rimetric '~ studies and 'H NMR spectral changes of certain macrocyclic polyethers in the presence of arenediazonium salt^.^,'^ Because of insufficient solubility of uncomplexed 2 it was not possible to probe for changes in the 'H NMR spectra of 1 and 2 in 172-dichloroethane upon addition of 18-crown-6. However, such measurements could be made in dimethyl sulfoxide and are summarized in Table V. Although the chemical shifts of the tert-butyl group hydrogens and the 3,5 aromatic ring hydrogens of 1 and 2 are unaffected by the presence of 18-crown-6, the 2,6 aromatic ring hydrogens are shifted upfield by 7-8 Hz in the presence of 18-crown-6. This chemical shift change for only the ortho hydrogens provides further evidence for the proposed diazonium ion-crown ether complex 5.

One‐Pot Oxidative Esterification and Amidation of Aldehydes

Abstract: During recent years, the direct transformation of aldehydes into esters or amides has developed into a vigorous research area and powerful one-pot oxidative esterification and amidation procedures have been reported. Several concepts that are often complementary in substrate scope, functional group tolerance, and reaction outcome have emerged, thus providing a wide range of alternatives to classical ester and amide synthesis via carboxylic acid intermediates.