RESUMO
The oxidation of alcohols to aldehydes using stoichiometric 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) in CH(2)Cl(2) at room temperature is a highly selective process favoring reaction at the carbinol center best able to accommodate a positive charge. The oxidation of aldehydes to carboxylic acids by 1 in wet acetonitrile is also selective; the rate of the process correlates with the concentration of aldehyde hydrate. A convenient and high yield method for oxidation of alcohols directly to carboxylic acids has been developed.
RESUMO
Benzylic ethers and related ArCH(2)OR substrates are oxidatively cleaved by 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) in wet CH(3)CN at room temperature to give the corresponding aromatic aldehyde and alcohol in high yield. Primary or secondary alcohol products are further oxidized by 1 to give carboxylic acids and ketones, respectively. The oxidation likely involves a formal hydride abstraction from the benzylic carbon as evidenced by slow reaction of substrates bearing electron-withdrawing substituents.
RESUMO
The oxoammonium cation of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) adds rapidly at room temperature in an ene-like fashion to trisubstituted alkenes to afford allylic alkoxyamines in high yield. [reaction: see text]