Unless the MnIII‐produced carbon‐radical from β‐ketocarbonyl compounds undergoes smooth intramolecular addition to alkenes, it traps molecular oxygen in the reaction medium to produce a peroxy radical, which reacts with the neighbouring carbonyl group to form 1,2‐dioxetane. Thermal decomposition of 1,2‐dioxetane completes the oxidation to produce α‐oxo ester. This oxidation seems to be general at 50 °C under aerobic conditions, and can be catalytic for MnIII in AcOH with ultrasonic irradiation. Thus, the development of a new synthetic method for diversely substituted furans has been accomplished based on a couple of the MnIII‐initiated domino oxidation of β‐ketocarbonyl compounds with a suitable α‐allylic substitution.

One pot syntheses of furan, thiophene, and pyrrole were accomplished by oxidative deacetylation using Mn(III)/Co(II) catalysts and the Paal-Knorr reaction from 1,5-dicarbonyl compounds, which are prepared from the conjugate addition of ethyl acetoacetate to α,β-unsaturated carbonyl compounds. The oxidative deacetylation and reductive cyclization of β-ketoesters derived from ethyl acetoacetate and o-nitrobenzyl bromides efficiently produced diversely substituted indoles.

The manganeseA C H T U N G T R E N N U N G (III)-mediated oxidation of b-keto esters becomes catalytic by the addition of a second cobalt(II) oxidant. This radical-initiated oxidation of b-keto esters is general under aerobic condition to produce a-oxo esters, which may consecutively undergo further heterocyclizations, either by intramolecular Diels-Alder reaction to dihydropyrans or by aromatic cyclization to furans depending upon the substitution pattern at the d-carbon. Since acetoacetates are very useful in carbon-carbon bond formation with allylic halides to give various b-keto esters, this one-pot catalytic oxidation and heterocy-A C H T U N G T R E N N U N G clization provides an efficient repertoire for the construction of diverse heterocyclic compounds.

Catalytic Oxidation of -Keto Esters by Manganese(III)/Cobalt(II) and Consecutive Cyclization to Heterocycles. --Keto esters are catalytically oxidized by Mn(III)/Co(II)-system to -oxo esters, which directly cyclize to dihydropyrans or furans. -(JU, Y.; MIAO, D.; SEO, J. G.; KOO*, S.; Adv. Synth. Catal. 356 (2014) 14-15, 3059-3066, http://dx.