Rita Skoda-Földes

NMR investigation of Pd(II)-Pd(0) reduction in the presence of mono- and ditertiary phosphines

The reduction of Pd(II) to Pd(0) was investigated in the presence of both monodentate (PPh3) and bidentate (dppp=1,3-bis(diphenylphosphino)propane) phosphines. It was shown by 31P NMR measurements that triphenylphosphine can reduce Pd(OAc)2 to zerovalent palladium in toluene and dppp is mainly responsible for the reduction in dmf resulting in dppp hemioxide and dppp dioxide. Both mono- and bidentate coordinations of dppp in intermediate species are proposed on the basis of in situ NMR studies. In the presence of two equivalents of silver triflate, the formation of the [Pd(dppp)(PPh3)2]2+ square-planar complex cation has been observed without any reduction of Pd(II) to Pd(0) species.

Oligomerisation of isobutene with silica supported ionic liquid catalysts

Bronsted acidic ionic liquids, supported on silica gel, have been used effectively in oligomerisation of isobutene. The supported catalysts could be used several times without loss of activity or change in selectivity. The ratio of the products could be influenced by the proper choice of the ionic liquid component of the catalyst and the reaction temperature.

Palladium-catalysed aminocarbonylation of steroidal 17-iodo-androst-16-ene derivatives in N,N′-dialkyl-imidazolium-type ionic liquids

The use of [bmim]+[BF4]−, [bmim]+[PF6]− and [emim]+[PF6]− ionic liquids as solvents in homogeneous catalytic aminocarbonylation of 17-iodo-5α-androst-16-ene at atmospheric carbon monoxide pressure has been investigated. It has been proved that after the extraction of the product with toluene, the ionic liquid–catalyst mixture could be recycled several times. Although there was a loss of catalytic activity in the further cycles, even 94% conversion can be achieved after the fifth run by using [bmim]+[BF4]− ionic liquid. The conversion depended strongly both on the properties of the ionic liquid and those of the catalyst. The activities of the in situ palladium(0) catalysts prepared from Pd(OAc)2 and various phosphine ligands (PPh3, TPPTS, DPPBA) have been compared. The method can be effectively used for the aminocarbonylation of other steroids with 17-iodo-16-ene functionality.

Facile Synthesis of Steroidal Phenyl Ketones via Homogeneous Catalytic Carbonylation

Steroidal phenyl ketones were synthesised in high yields by palladium-catalysed carbonylation reactions of 17-iodo-androst-16-ene derivatives in the presence of NaBPh4 under mild reaction conditions. Alkenyl bromides or enol triflates gave lower yields in the same reaction.

Facile synthesis of novel ferrocene α-ketoamides via homogeneous catalytic carbonylation

Abstract An efficient synthesis of novel ferrocene α-ketoamides is described. They were synthesised in good yields via a palladium-catalysed carbonylation reaction. The ratio of the main products and the ferrocene amides, obtained as minor compounds in most cases, depends on the catalyst and on the structure of the amine reagent.

Homogeneous catalytic dehalodimerization of 17-iodo-Δ16 steroids

Abstract 17-Iodo- Δ 16 steroids undergo selective dimerization and carbonylative dimerization in the presence of palladium catalysts in dimethylformamide which result in 16–17′-coupled dienes and 17-carboxylic anhydrides, respectively. Moderate to good yields have been obtained for both types of dimers.

Palladium-catalyzed homogeneous coupling reactions of steroids with organostannanes

Direct and carbonylative coupling reactions of various steroid derivatives possessing iodo- and bromo-alkenyl moiety (17-iodo-androst-16-ene, 1, 17-bromoandrost-2,16-diene, 2, 17-iodo-4-aza-4-methylandrost-16-en-3-one, 3, 17-iodo-4-azaandrost-16-en-3-one, 4) with vinyltributylstannane and ethynyltributylstannane were carried out in the presence of various palladium catalysts. While carbonylation took place only with vinyltributylstannane, 17-vinyl-, and 17-ethynyl-delta 16 steroids were produced via direct coupling with vinyltributylstannane and ethynyltributylstannane, respectively. Activities of some catalysts based on Pd(0) and Pd(II) precursors were compared, and Pd(PPh3)4 was found to be superior to other complexes in most cases. In the coupling of 17-iodoandrost-16-ene with organostannanes Pd2(dba)3 + 8 AsPh3 in situ catalyst was found to be even more effective.

Homogeneous catalytic hydrosilylation of the CC double bond in the presence of transition metalcatalysts

Abstract Hydrosilylation of unsaturated esters and other vinyl- and vinylidene type olefins has been carried out with PtCl2(PhCN)2, RhCl(PPh3)3 and platinum-phosphine catalysts. With PtCl2(PhCN)2 and platinum(0)-phosphine complexes as catalysts the hydrosilylation of methyl methacrylate gave the linear product 2a, whereas in the RhCl(PPh3)-catalyzed reaction the silyl ketene acetal derivative 4a was formed selectively. In the reactions of other esters and unsaturated hydrocarbons the main product is highly dependent on the structure of the substrate, but the catalyst used is also very important. With unsaturated hydrocarbons the selectivity is rather poor, but in the case of 1-vinyl-2-pyrrolidinone the linear- (9e) and the branched hydrosilylated derivative (10e) are formed in high yields depending on the catalyst used. The platinum(II)-phosphine complexes are inactive in the absence of air, but some platinum(0)-phosphine catalysts are also effective under argon in the hydrosilylation of methyl methacrylate.

Facile, high-yielding synthesis of novel pentacyclic steroids

Abstract Novel androstane-based skeletons were synthesized in a facile one-pot reaction of 17-iodo-androsta-16-ene, vinyltributylstannane and functionalised olefins. The palladium-catalysed coupling reaction was followed by Diels-Alder reaction resulting in the formation of an unsaturated six-membered E-ring.

Functionalization of the estrone skeleton via homogeneous coupling and hydroformylation reactions

Abstract The estrone triflate (3-trifluoromethylsulfonate-estra-1,3,5(10)-triene-17-one) was vinylated by use of vinyltributyltin in the presence of palladium catalysts. The rhodium- and platinum-catalysed hydroformylation of the vinylated aromatic steroid gave the pure epimer 3-(2′-formylethyl)-estra-1,3,5(10)-triene-17-one.