Palladium/Iron-Catalyzed Wacker-Type Oxidation of Aliphatic Terminal and Internal Alkenes Using O₂

Abstract

The Wacker-type oxidation of aliphatic terminal alkenes proceeds using a Pd/Fe catalyst system under mild reaction conditions using 1 atm O 2 without other additives. The use of 1,2-dimethoxyethane/H 2 O as a mixed solvent was effective. The slow addition of alkenes is also important for improving product yields. Fe(III) citrate was the most efficient cocatalyst among the iron complexes examined, whereas other complexes such as FeSO 4 , Fe 2 (SO 4 ) 3 , Fe(NO 3 ) 3 , and Fe 2 O 3 were also operative. This method is also applicable to aliphatic internal alkenes, which are generally difficult to oxidize using conventional Pd/Cu catalyst systems. The gram-scale synthesis and reuse of the Pd catalysts were also demonstrated.

Selective Palladium(II)‐Catalyzed Dimerization of Styrenes and Acrylates in Molten Tetrabutylammonium Acetate as an Ionic Liquid

“…These findings are in line with the literature, where iron(III) and copper(II) salts are commonly employed as well as molecular oxygen. [32,33] However, when tested in ionic liquid, iron salts and molecular oxygen yielded poor results (Table 2, runs 5-7,13). Furthermore, silver carbonate and common organic oxidants failed (Table 2, runs 8-10), while the use of peroxides led to the formation of styrene oxide and byproducts, as expected (Table 2, runs [11][12].…”

Hexa-Fe(III) Carboxylate Complexes Facilitate Aerobic Hydrocarbon Oxidative Functionalization: Rh Catalyzed Oxidative Coupling of Benzene and Ethylene to Form Styrene

“…There are limited examples of co-oxidants capable of rapid reaction with metal hydrides that also have oxidation potentials amenable to aerobic reoxidation. , There are a few reports of Fe-based oxidants for transition-metal catalyzed processes. For example, Pd-catalyzed Wacker oxidation has been reported using simple Fe salts in addition to Fe­(II) phthalocyanine under aerobic conditions in the presence of 1,4-benzoquinone. ,, Also, the Bäckvall group has reported aerobic Pd-catalyzed arene–olefin and olefin–olefin oxidative coupling reactions using Fe­(II) phthalocyanine additive, which was proposed to react with dioxygen to form a species capable of reoxidizing hydroquinone to 1,4-benzoquinone, the proposed direct oxidant. − …”

“…For example, Pd-catalyzed Wacker oxidation has been reported using simple Fe salts in addition to Fe(II) phthalocyanine under aerobic conditions in the presence of 1,4-benzoquinone. 5 , 10 , 11 Also, the Bäckvall group has reported aerobic Pd-catalyzed arene–olefin and olefin–olefin oxidative coupling reactions using Fe(II) phthalocyanine additive, which was proposed to react with dioxygen to form a species capable of reoxidizing hydroquinone to 1,4-benzoquinone, the proposed direct oxidant. 12 − 14 …”