Carlo Botteghi

Homogeneous catalytic hydrogenation of free carboxylic acids in the presence of cluster ruthenium carbonyl hydrides

Abstract Saturated monocarboxylic acids up to C 6 , several bicarboxylic acids and some of the corresponding anhydrides are hydrogenated in the homogeneous phase with H 4 Ru 4 (CO) 8 (PBu 3 ) 4 as catalyst to give the corresponding alcohols (present among the reaction products as esters) or lactones at 100–200°C under a pressure of 100–200 atm of hydrogen. Anhydrides react at temperatures lower than those needed for acids. Esters are not reduced. Only δ-valerolactone is hydrogenated to 1,5-pentanediol. Ruthenium carbonyl carboxylates have been recovered at the end of the reaction and appear to be catalytically active intermediates.

Optically active nitrogen ligans: III. Enantioface-discriminating transfer hydrogenation of acetophenone catalyzed by rhodium(I) complexes with chiral 2-(2′-pyridyl)pyridines

Abstract The reduction of acetophenone by hydrogen transfer from isopropranol is catalyzed by rhodium(I) complexes containing optically active 2-(2′-pyridyl)pyridines. Optical yields up to 15% have been obtained.

Metals in organic syntheses: XIV. NMR, IR, and reactivity studies on the olefin hydroformylation catalyzed by Pt-Sn complexes☆

Abstract Among the several hydrides formed when trans-[PtHClL2] (L = PPh3) reacts with Sncl2, only trans-[PtH(SnCl3)L2] rapidly inserts ethylene, at −80°C, to yield cis-[PtEt(SnCl3)L2]. At −10°C, cis-[PtEt(SnCl3)L2] irreversibly rearranges to the trans-isomer, thus indicating that the cis-isomer is the kinetically controlled species, and that the trans-isomer is thermodynamically more stable. At −50°C, a mixture of trans-[PtHClL2] and trans[PtH(SnCl3)L2] reacts with ethylene to give cis-[PtEtClL2] and cis-[PtEt(SnCl3)L2] and this has been attributed to the catalytic activity of SnCl2 which dissociates from cis-[PtEt(SnCl3)L2] at this temperature. Carbon monoxide promotes the cis-trans isomerization of cis[PtEt(SnCl3)L2], which occurs rapidly even at −80°C. This rearrangement is followed by a slower reaction leading to the cationic complex trans-[PtEt(CO)L2]+ SnCl3−. At −80°C, this complex does not react further, but when it is kept at room temperature ethyl migration to coordinated carbon monoxide takes place, to give several Pt-acyl complexes, i.e. trans-[PtCl(COEt)L2], trans-[Pt(SnCl3)(COEt)L2], trans-[PtCl(COEt)l2 · SnCl2], and trans-[Pt(COEt)(CO)L2]+ SnCl3−. This mixture of Pt-acyl complexes reacts with molecular hydrogen to yield n-propanal and the same complex mixture of platinum hydrides as is obtained by treating trans-[PtHClL2] with SnCl2. Trans-[PtH(SnCl3)L2] reacts with carbon monoxide to yield the five-coordinate complex [PtH(SnCl3)(CO)2L2], which has been characterized by NMR and Ir spectroscopy; ethylene does not insert into the PtH bond of this complex at low temperature. At room temperature, trans-[PtH(SnCl3)L2] reacts with a mixture of CO and ethylene to yield the same mixture of Pt-acyl species as is obtained when trans-[PtEt(SnCl3)L2] is allowed to react with CO. The role of a PtSn bond in these reactions is discussed in relation to the catalytic cycle for the hydroformylation of olefins.

Asymmetric synthesis by chiral ruthenium complexes : II. Enantioselective hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium complexes containing the ligand ()-diop

Abstract Cluster rutheniumcarbonyl hydrides complexes containing ()-DIOP as asymmetric ligand are efficient catalysts for asymmetric reduction of α,β-unsaturated acids at 90–120°C under hydrogen pressure. Optical yields up to 68% have been achieved. The course of the reaction has been investigated by IR spectroscopy using a high pressure cell.

Platinum(II) trichlorostannate chemistry. On the importance of the Pt-Sn linkage in hydroformylation chemistry and a novel PtC(OSnCl2)R-carbene

Summary The reaction of trans -PtCl(COR)(PPh 3 ) 2 ( 1 ) (R = a , C 6 H 5 ; b , C 6 H 4 - p -NO 2 ; c C 6 H 4 - p -CH 3 ; d , C 6 H 4 - p -OCH 3 ; e , CH 3 , f , Et; g , Pr n ; h , Hex n ; i , CH 2 CH 2 Ph; j , Bu t ) with SnCl 2 and SnCl 2 plus H 2 are described. The reactions with SnCl 2 alone afford a mixture of trans -Pt(SnCl 3 )(PPh 3 ) 2 ( 2 ), and trans -PtCl(C(OSnCl 2 )-R)(PPh 3 ) 2 ( 3 ) with 3 having tin oxygen bond. For 1f, 1h and 1j , reactions with SnCl 2 plus H 2 give aldehydes and platinum(II) hydride complexes, whereas for 1b and 1d , no aldehydes are obtained. The significance of these results in relation to H 2 activation in the hydroformylation reaction is discussed. 31 P, 119 Sn, 195 Pt and, in a few cases, 13 C NMR data are presented.

On the mechanism of platinum(II)/SnCl2 catalyzed hydroformylation of olefins. Studies of the reactivity of alkyl complexes containing chelating diphosphines

The complexes cis-PtCl(C2H5)(diphosphine) (diphosphine = 1,3-bis(diphenylphosphino)propane and 1,4-bis(diphenylphosphino)butane) have been used as model compounds for the hydroformylation of olefin catalyzed by the system PtCl2/diphosphine/SnCl2. They react with SnCl2 to yield the corresponding trichlorostannate complexes cis-Pt(SnCl3)(C2H5)(diphosphine), which in the absence of free ethylene decompose to form the dichloro species cis-PtCl2(diphosphine) via an unstable hydrido species. Both the chloro- and trichlorostannate-alkyl complexes react with CO to give the acyl species cis-PtX(COC2H5)(diphosphine) (X = Cl or SnCl3). When the diphosphine is 1,4-bis(diphenylphosphino)butane, oligomeric acyl complexes of trans geometry are formed. Preliminary studies of the reactivity of the acyl complexes with molecular hydrogen show that only the complexes bearing the Pt—SnCl3 moiety react at ambient conditions giving propanal as the only observed organic product.

Rhodium-catalyzed michael additions of activated nitriles to α,β - unsaturated esters

The Michael additions of activated nitriles to methyl acrylate (MA) and methyl vinyl ketone (MVK) proceeds with fair to high yields (46–92%) in the presence of catalytic amount of HRh(CO)(PPh3)3 1 under mild eaction conditions.

Optically active aldehydes via hydroformylation of 1,3-dienes with chiral diphosphinerhodium complexes

Abstract Optically active aldehydes have been obtained by hydroformylation of simple aliphatic conjugated dienes under standard oxo conditions (90 atm (CO/H 2  1/1) and 95°C), using HRh(CO)(PPh 3 ) 3 /()DIOP as catalyst. The highest optical yield (32%) was achieved in the preparation of 3-methylpentanal from isoprene.

Synthesis of homochiral pyridyl, bipyridyl and phosphino derivatives of 2,2-dimethyl-1,3-dioxolane: Use in asymmetric catalysis

Abstract Homochiral pyridyl, bipyridyl and phosphino derivatives of 2,2-dimethyl-1,3-dioxolane were prepared from L-(+)-tartrate. These compounds were assessed in metal catalyzed asymmetric addition of diethylzinc to benzaldehyde, hydroformylation of styrene, hydrocarboethoxylation of styrene and allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate.

Asymmetric synthesis by chiral ruthenium complexes : III. Regioselectivity and asymmetric induction in catalytic hydrogenation of α,β-unsaturated dicarboxylic acids

Abstract The homogeneous catalytic hydrogenation of citraconic and mesaconic acids in the presence of H4Ru4(CO)8[(—)-DIOP]2 gives, in addition to (—)(S)-methylsuccinic acid, a mixture of λ-lactones in ratios which depend on the substrate and the reaction temperature. An exceptionally high regioselectivity is obtained in the hydrogenation at 120°C of the more hindered carboxyl group of mesaconic acid.