Cerium‐Catalyzed, Aerobic Oxidative Synthesis of 1,2‐Dioxane Derivatives from Styrene and Their Fragmentation into 1,4‐Dicarbonyl Compounds

Abstract

1,4‐Diketones were prepared by cerium‐catalyzed oxidative coupling of styrene with molecular oxygen and 1,3‐dicarbonyl compounds. This two‐step sequence was performed as a one‐pot procedure without isolation of the intermediate products. The first step is a metal‐catalyzed radical reaction yielding 3‐hydroxy‐1,2‐dioxane derivatives being the cyclotautomers of initially formed 4‐hydroperoxy ketones. In the second step of this sequence, these endoperoxides are converted with AcCl–pyridine by Kornblum–DeLaMare fragmentation into the 1,4‐dicarbonyl motif. Several intermediate 1,2‐dioxane derivatives could be isolated and structurally characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Formation of δ‐Lactones with anti‐Baeyer–Villiger Regiochemistry: Investigations into the Mechanism of the Cerium‐Catalyzed Aerobic Coupling of β‐Oxoesters with Enol Acetates

“…One compound is monocyclic ( 15 c ), two are annulated ( 15 a and 15 b ), and two others are spirocyclic ( 15 d and 15 e ). The structures were already published earlier and crystal data have been deposited . Structural similarities are apart from the 1,2‐dioxane ring the tertiary alcohol at C9, the quaternary carbon center C5 carrying an ester moiety and a phenyl substituent at C3.…”

“…Although the exact mechanism of this radical chain reaction leading to intermediate product 6 remains unclear, we have experimental precedence for its existence. We have isolated and fully characterized several analogues earlier including X‐ray diffraction data in some cases ,. However, with the assumption of intermediate product 6 , the 1,4‐diketone 5 is formed by hydrolysis of the two acetal moieties of endoperoxide 6 (actually, we were able to detect hydrogen peroxide in the reaction mixture in these cases).…”

TBAI/TBHP‐Promoted Generation of Malonyl Radicals: Oxidative Coupling with Styrenes Leads to γ‐Keto Diesters

“…Alternatively, oxidative radical difunctionalization of cheap and readily available alkenes with simple malonates might provide a better route to access them. While difunctionalization of styrenes with α‐cyanoesters, β‐ketoesters and 1,3‐dicarbonyl compounds– have been quite known, reports showing similar coupling with malonic esters are scarce. Only one example to date is reported in the literature by Nair, where CAN was used to activate the malonate‐C−H bond and to install the keto functionality into styrene.…”

Polyethylene Glycols as Efficient Media for Decarboxylative Nitration of α,β-Unsaturated Aromatic Carboxylic Acids by Ceric Ammonium Nitrate in Acetonitrile Medium: A Kinetic and Mechanistic Study

“…Being good Michael acceptors, , -unsaturated nitroalkenes are widely applied in organic synthesis [12]. Among various methods reported for their preparation, a method involving the use of CAN provides a practical way to the synthesis of , -unsaturated "nitroalkenes" in goodto-excellent yields [13][14][15][16][17][18][19][20][21][22][23].…”