MCM-41-supported bidentate phosphine palladium(0) complex: a highly active and recyclable catalyst for the Sonogashira reaction of aryl iodides

The first MCM-41-supported bidentate phosphine palladium(0) complex has been prepared. This complex is a highly efficient catalyst for Sonogashira reaction and can be reused at least 10 times without any decrease in activity.     

Reactions of esters of tetracoordinated phosphorus acids with nucleophilic reagents in highly organized media

Characteristic features of reactions involving esters of phosphorus-containing acids in highly organized media (micelles, liquid crystals, vesicles, and emulsions) are surveyed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 298–312, February, 1996.     

First lipase catalysed resolution of epoxy enol esters

We report the first enzyme-catalysed kinetic resolution of epoxy enol esters. The lipase-promoted hydrolysis of these compounds provided α-hydroxyketones or α-hydroxyaldehydes (arising from the spontaneous rearrangement of the epoxy enols) and the residual esters with moderate to good enantioselectivity (E up to 100).     

A kinetic approach to homogeneous Ziegler type polymerization. Steady state

In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is discussed and the equations are fitted to the experimental results.     

Isomerisation of ω-hydroxyalkenes under hydroxycarbonylation conditions in palladium catalysed aqueous phase systems

The ω-hydroxyolefins 3-buten-1-ol, 3-buten-1-methyl-1-ol and 4-penten-1-ol were subjected to hydroxycarbonylation conditions in water in the presence of PdCl₂(PhCN)₂ and 4-8 equiv. of water soluble tris(3-sodiumsulfonatophenyl)phosphine (TPPTS), or N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P). Under conditions of high conversion, the olefins primarily undergo isomerisation through a chain walking mechanism with selectivities for aldehyde ranging from 65% to 98%, with the lower values for longer chain alcohols. The lactones formed as the minor product are almost exclusively branched, indicating that in the first step 2,1-insertion is strongly favoured over 1,2-insertion. In the N3P system also linear lactone is produced at lower conversion. Running the reaction in D₂O produces multiple deuterium incorporation in all positions of the carbon chain. A mechanism is discussed.     

N-Heterocyclic carbene-palladium complex on polystyrene resin surface as polymer-supported catalyst and its application in Suzuki cross-coupling reaction

A poly(imidazoliummethyl styrene)-surface grafted-polystyrene resin was prepared by suspension polymerization. This was used as the polymer-supported carbene precursor for the palladium complex, which efficiently catalyzed the Suzuki cross-coupling of aryl halides and phenylboronic acid.     

Synthesis and applications of C2-symmetric guanidine bases

The preparation of the tetracyclic C₂-symmetric guanidinium salts 5 and 11-13 is reported together with their application to enantioselective transformations.     

Electrocatalytic dehalogenation of α-bromoketones in the presence of Cp2TiCl2

Processes of direct and electrocatalytic (in the presence of electrochemically reduced Cp₂TiCl₂) reduction of three α-bromoketones containing the C(sp³)-Br or C(sp²)-Br bond, viz., 2-bromo-and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-ones and α-bromo-acetophenone, were studied by cyclic voltammetry and preparative electrolysis. In all cases, the dissociative electron transfer proceeds via the concerted mechanism. Preparative electrolysis of these α-bromoketones in the presence of Cp₂TiCl₂ affords the reductive debromination products in 40–80% yield at low cathodic potentials (−0.85 V vs. Ag/AgCl/KCl). In the case of 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one in the potentiostatic regime, only one bromine atom can be eliminated selectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 977–983, May, 2007.     

An expeditious preparation of E-2-amino-5-hydroxyadamantane and its Z-isomer

Reductive amination of 5-hydroxy-2-adamantanone with S-α-methylbenzylamine using 5% Rh-C as the catalyst in the presence of Al(iOPr)₃ gave a 3:1 mixture of the E- and Z-5-hydroxy-adamantane-1-phenethylamines. Choice of catalyst, concentration, solvent and the presence of the hydroxyl group on the adamantane influenced the stereoselectivity of the amination reaction. The desired E-isomer could be isolated by fractional crystallization from diisopropyl ether. Debenzylation gave the elusive E-2-amino-5-hydroxyadamantane in a 45% overall yield.