Catalytic hydration of diethyl maleate to diethyl malate using divalent complexes of palladium(II) as catalysts

Abstract

The complexes [Pd (µ-) (L-L) ] 22+ (L-L = dppe, dcpe) act as catalysts in aqueous THF solution for the addition of water to the carbon-carbon double bond of diethyl maleate to give the alcohol, diethyl malate. This addition reaction of diethyl maleate to give diethyl malate, as well as its oxidation to diethyl oxaloacetate, is catalyzed in aqueous THF solution by a mixture of PdCU2-and CuCl2. Isomerization of diethyl maleate to diethyl fumarate, along with hydrolysis products of each alkene, is also observed with both catalyst systems. Mechanisms for these palladium(II) catalyzed reactions involving the protonolysis of an intermediate alkylpalladium complex are proposed. In aqueous solution, tertiary phosphines catalyze the cis-trans isomerization of diethyl maleate to diethyl fumarate.

Kinetic and Mechanistic Study of the H-Transfer Reduction of Dimethyl Itaconate by a Rh/TPPTS Catalyst under Biphasic Conditions: Evidence for a Rhodametallacycle Intermediate

“…This result is confirmed by the lack of incorporation at C 3 when H 2 O/DCOO -is used. Hydrolysis of alkyl complexes of transition metals such as palladium (II) [27] and selective incorporation of H ϩ in Rh-alkyl fragments [28] has already been reported.…”

Gold(I)-catalyzed hydration of allenes

“…Complexes of a number of transition metals including Pt(II),2,3 Hg(II),3,4 Au(I),5 and Ru(II)6 catalyze the hydration of alkynes, but these methods are not effective for alkenes. Palladium(II) salts promote the addition of water to ethylene and unactivated 1-alkenes, but facile β-hydride elimination leads to oxidation and formation of ketones 7. Reports of platinum-catalyzed anti-Markovnikov hydration of 1-hexene8 have not been validated,9 and as such, transition metal-catalyzed alkene hydration has been restricted to electron deficient alkenes such as maleate esters 10…”

Stabilization of Metal Nanoparticles in Aqueous Medium by Polyethyleneoxide–Polyethyleneimine Block Copolymers

“…However, up to now amphiphilic block copolymers were successfully employed only in nonpolar organic solvents, because appropriate polymers with the ability to form micelles in water and the ability to bind metals in the micelle core were not available. On the other hand, water as a reaction medium has a number of advantages in a wide range of various catalytic reactions: hydrogenation, oxidation, gas-shift reaction (23)(24)(25). Over and above the solubility problems, environmental considerations play an important role as well.…”