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The scope of carbon monoxide‐free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2‐bis‐((2,5)‐diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. [ABSTRACT FROM AUTHOR]

The hydroformylation of propene to give predominantly iso‐butanal has been achieved; class‐leading selectivity is possible even at higher temperatures that deliver fast conversion. Racemic rhodium complexes of bidentate phospholane phosphites derived from tropos‐biphenols and unusual solvent systems are the key to the selectivity observed. [ABSTRACT FROM AUTHOR]

This paper reports experimental and computational studies on the mechanism of a rhodium-catalyzed hydroformylation that is selective for branched aldehyde products from unbiased alkene substrates. This highly unusual selectivity relies on a phospholane-phosphite ligand prosaically called BOBPHOS. Kinetic studies using in situ high pressure IR (HPIR) and the reaction progress kinetic analysis methodology suggested two steps in the catalytic cycle were involved as turnover determining. Negative order in CO and positive orders in alkene and H2 were found and the effect of hydrogen and carbon monoxide partial pressures on selectivity were measured. Labeling studies found rhodium hydride addition to the alkene to be largely irreversible. Detailed spectroscopic HPIR and NMR characterization of activated rhodium-hydrido dicarbonyl species were carried out. In the absence of H2, reaction of the rhodiumhydrido dicarbonyl with allylbenzene allowed further detailed spectroscopic characterization of four- and five-coordinate rhodium-acyl species. Under single-turnover conditions, the ratios of branched to linear acyl species were preserved in the final ratios of aldehyde products. Theoretical investigations uncovered unexpected stabilizing CH-π interactions between the ligand and substrate which influenced the high branched selectivity by causing potentially low energy pathways to become unproductive. Energy span and degree of TOF control analysis strongly support experimental observations and mechanistic rationale. A three-dimensional quadrant model was built to represent the structural origins of regio- and enantioselectivity. [ABSTRACT FROM AUTHOR]

An abstract of the article "Rapid Asymmetric Transfer Hydroformylation (ATHF) of Disubstituted Alkenes Using Paraformaldehyde as a Syngas Surrogate" by Rachael Pittaway and colleagues is presented.

Abstract: The reactions of the very bulky phosphine ligands containing both tert-butyl and ortho-trifluoromethylphenyl substituents with [PdCl2(PhCN)2] have been studied, in order to assess the impact of steric and electronic effects on a ligand''s coordination ability. The palladium complexes of tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine and tert-butyl(ortho-trifluoromethylphenyl)(n-butyl)phosphine were characterised by X-ray crystallography and shown to be good precatalysts for the hydroxy- and alkoxycarbonylation of alkenes relative to Pd complexes of tricyclohexylphosphine and triphenylphosphine. A notable feature of Pd complexes of tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine is significantly enhanced regioselectivity relative to previous state-of-the-art catalysts in the hydroxycarbonylation of styrene, even if lithium chloride co-catalysts are not used. These catalysts derived from large cone angle ligands consistently give higher regioselectivity in the alkoxycarbonylation of styrene using ethanol, n-propanol, and i-propanol as nucleophiles. These Pd complexes are also active in the Suzuki coupling of activated aryl chlorides, and in both carbonylation and Suzuki reactions, tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine gives more productive catalysts than its bulkier analogues. [Copyright &y& Elsevier]