Tandem sequence of phenol oxidation and intramolecular addition as a method in building heterocycles.

A tandem phenol oxidation-Michael addition furnishing oxo- and -aza-heterocycles has been developed. Dirhodium caprolactamate [Rh(2)(cap)(4)] catalyzed oxidation by T-HYDRO of phenols with alcohols, ketones, amides, carboxylic acids, and N-Boc protected amines tethered to their 4-position afforded 4-(tert-butylperoxy)cyclohexa-2,5-dienones that undergo Brønsted acid catalyzed intramolecular Michael addition in one-pot to produce oxo- and -aza-heterocycles in moderate to good yields. The scope of the developed methodology includes dipeptides Boc-Tyr-Gly-OEt and Boc-Tyr-Phe-Me and provides a pathway for understanding the possible transformations arising from oxidative stress of tyrosine residues.

Dirhodium-catalyzed phenol and aniline oxidations with T-HYDRO. Substrate scope and mechanism of oxidation.

Dirhodium caprolactamate, Rh(2)(cap)(4), is a very efficient catalyst for the generation of the tert-butylperoxy radical from tert-butyl hydroperoxide, and the tert-butylperoxy radical is a highly effective oxidant for phenols and anilines. These reactions are performed with 70% aqueous tert-butyl hydroperoxide using dirhodium caprolactamate in amounts as low as 0.01 mol % to oxidize para-substituted phenols to 4-(tert-butyldioxy)cyclohexadienones.