Sergio Bertozzi

Selective hydroformylation of open-chain conjugated dienes promoted by mesitylene-solvated rhodium atoms to give β,γ unsaturated monoaldehydes

The hydroformylation of 1,3-butadiene, 2-methyl-1,3-butadiene and 1,3-pentadiene using rhodium vapour-mesitylene cocondesates as a catalytic precursor is reported. The reaction gives β,γ-unsaturated monoaldehydes with high chemoselectivity and regioselectivity. η3-Butenyl complexes, derived from the addition of RhH species to the conjugated double-bound system, are likely to be intermediates, as suggested by deuterioformylation experiments.

1-Hexene rhodium-catalyzed hydroformylation at partial substrate conversion: influence of reaction parameters on the chemoselectivtty and regioselectivity

Abstract The influence of the reaction parameters (temperature, gas pressure) on the chemo- and regioselectivity of 1-hexene hydroformylation in the presence of Rh4(CO)12 as catalytic precursor has been investigated at partial and complete conversion. Both chemo- and regioselectivity are independent of the substrate conversion until 1-hexene is present in the reaction mixture. Chemoselectivity to aldehydes is complete at room temperature, while at higher temperatures it decreases with decreasing pressure and increasing temperature as a consequence of 1-hexene isomerization to (E)- and (Z)-2-hexenes. Similar amounts of heptanal and 2-methylhexanal are obtained at room temperature. At higher temperature and partial substrate conversion, only 1-hexene is converted to aldehydes; the regioselectivity towards the linear isomer increases from 4% at room temperature to 48% at 120 °C and is not affected by the gas pressure. Differing behaviours of the linear and branched alkyl metal intermediates towards the β-hydride elimination under the reaction conditions account for the influence of the reaction parameters on the chemo- and regioselectivity in 1-alkene hydroformylation.

A simple method of regenerating arenerutheniuim dichloride dimers, [RuCl2(η6-arene)]2, from their monomeric adducts with amines or tertiary phosphines, RuCl2(η6-arene)L

Abstract The monomeric amine or tertiary phosphine complexes RuCl2(η6-arene)L (arene  benzene, p-cymene) can be reconverted into their dimeric precursors [RuCl2(η6-arene)]2 by heating with 1,5-cyclooctadiene (COD), 2-propanol, and anhydrous Na2CO3 and subsequent treatment of the resulting ruthehium(0) complexes Ru(η6-arene) (η4-COD) with HCl; the ligandL can be recovered.

Diastereoselectivity in the rhodium-catalyzed hydroformylation of (+)(R)-1-phenylethyl vinyl ether

Abstract The degree of diastereoselectivity in the rhodium-catalyzed hydroformylation of (+)( R )-1-phenylethyl vinyl ether is much higher than that in the hydroformylation of the related olefin, 4-phenyl-1-pentene.

Unexpected cyclocotrimerization of α,ω-dialkynes and nitriles to alkynylpyridines catalyzed by arene-solvated cobalt atoms

Abstract Arene solvated cobalt atoms have been found to promote an unusual conversion α,ω-dialynes and nitriles to alkynyl-subsituted pyridines.

Synthesis of new chiral (η6-arene)(η4-diene)ruthenium(O) complexes

Abstract New Ru(η6-arene)(η4-diene) complexes, containing chiral substituents on the aromatic ring, have been prepared and characterized. The 1H NMR inequivalence of the ortho and meta protons of the phenyl ring is discussed.

Cobalt atoms as catalysts of the synthesis of pyridines from nitriles and acetylenes

Abstract Cobalt atoms have been found to provide efficient and selective catalysts for the synthesis of pyridines from nitriles and acetylenes; the reaction conditions are milder than those reported for other cobalt-containing catalysts.

Factors affecting the regioselectivity in the rhodium-catalysed hydroformylation of vinyl ethers

Abstract The rhodium catalysed hydroformylation of vinyl ethers ROCHCH2, where R is an alkyl, a benzyl or a phenyl group, has been investigated over the 20–100°C temperature range in the presence of Rh4(CO)12 or [Rh(CO)2Cl]2/PPh3 ( 1 6 ) as catalytic precursors. A mixture of 2-alkoxy-(or phenoxy)propanal (the α-isomer) and 3-alkoxy-(or phenoxy)propanal (the β-isomer) is obtained in good yield. The isomeric composition of the aldehydes depends on the structure of the substrate, on the catalytic precursor employed, and on the reaction temperature. The α-isomer predominates in all the cases, its predominance being greater (i) at low temperatures, (ii) in the presence of Rh4(CO)12 as catalyst precursor, and (iii) when a phenyl group is present in the β or γ position with respect to the double bond in the substrate. Electronic factors arising from the presence in the substrate of the oxygen atom and a phenyl group are more important than the steric hindrance of the R group in determining the regioselectivity of the reaction.

Synthesis of 3-Phenyl and 5-Phenyl-2-pyrrolidinone via Rhodium Catalysed Carbonylation of Allylamines

Abstract The Rh4(CO)12 catalysed reaction with CO and H2 of 1-phenyl- and 3-phenyl allylamine gives 5-phenyl- and 3-phenyl-2-pyrrolidinone respectively, in good yield. A reasonable reaction pathway of the carbonylation reaction is presented.

Remarkable α-regioselectivity in the rhodium-catalyzed hydroformylation of 2-vinylpyridine

Abstract The [{Rh(CO) 2 Cl} 2 ]/PPhMe 2 -catalyzed hydroformylation of 2-vinylpyridine gives the branched aldehyde 2-(2-pyridyl)propanal in good yield and 99% α-regioselectivity.