91143-05-4

One-pot procedures bear the potential to rapidly build up molecular complexity without isolation and purification of consecutive intermediates. Here, we report multicatalytic protocols that convert alkenes, unsaturated aliphatic alcohols, and aryl boronic acids into secondary benzylic alcohols with high stereoselectivities (typically >95:5 er) under sequential catalysis that integrates alkene cross-metathesis, isomerization, and nucleophilic addition. Prochiral allylic alcohols can be converted to any stereoisomer of the product with high stereoselectivity (>98:2 er, >20:1 dr).

Formic acid (FA) is one kind of important bulk chemicals, which is recognized as a sustainable and eco-friendly energy carrier to transport H2 via dehydrogenation or CO via decarbonylation. Expectantly, FA upon decomposition into H2 and CO could be used as the syngas alternative for hydroformylation. In this paper, the behaviors of FA to release H2 as well as CO following the distinct pathways were carefully investigated for the first time, and then established a new hydroformylation protocol free of syngas. It was found that the atmospheric hydroformylation of olefins with formic acid (FA) as syngas alternative was smoothly fulfilled over Xantphos (L1) modified Rh-catalyst under mild conditions (80 °C, Rh concentration 1 mol %, 14 h), resulting in >90% conversion of the olefins along with the high selectivity to the target aldehydes (>93%). By using FA as syngas source, the side-reaction of olefin-hydrogenation was greatly depressed. The in situ FT-IR and the high-pressure 1H NMR spectroscopic analyses were applied to reveal how FA behaves dually as CO surrogate and hydrogen source over L1-Rh(acac)(CO)2 catalytic system, based on which the deeply insight into the catalytic mechanism of hydroformylation of olefins with FA as syngas alternative was offered.

Concise syntheses of four tetrahydropyranyl diarylheptanoids isolated from Dioscorea villosa have been described. The key features include Prins cyclization to construct the tetrahydropyran cores, Keck asymmetric allylation, and Mitsunobu inversion. Optimization of the Prins cyclization conditions in order to minimize racemization has been described. Our syntheses also confirmed the absolute stereochemistry of the natural products.

A variety of primary alcohols have been investigated as convenient substrates for the ex situ delivery of carbon monoxide and molecular hydrogen in a two-chamber reactor. The gaseous mixture is liberated in one chamber by an iridium-catalysed dehydrogenative decarbonylation of the alcohol and then consumed in the other chamber in either a rhodium-catalysed hydroformylation of olefins or a palladium-catalysed reductive carbonylation of aryl halides. Hexane-1,6-diol was found to be the optimum alcohol for both reactions where moderate to excellent yields were obtained of the product aldehydes. A relatively low pressure of 1.5-2.4 bar was measured in the closed system during the two transformations.

The enantioselectivity of the asymmetric hydroformylation of 4-substituted styrenes in the presence of an in situ catalyst, formed from PtCl(SnCl 3)[(2S,4S)-BDPP] and tin(II) chloride, was influenced by the reaction temperature. The preferred formation of the S and the R enantiomers of the branched aldehyde regioisomers (2a-g) was observed at low and high temperatures, respectively. The electron-donor or electron-acceptor properties of the para substituents of styrene show correlation with the changes in enantioselectivity, especially with the reversal temperature of the enantioselectivity. The reversibility of the formation of the Pt-branched alkyl intermediates, leading to the corresponding R and S enantiomers of 2-arylpropanals, depends on the Hammett constants. The electronic effect of para substituents was investigated by quantum chemical methods employing the simple olefin adducts [HPt(PH 3)2(olefin)(SnCl3)]. Excellent linear correlation was found between the para substituent constants and the electrostatic potential at nuclei of the platinum atom. Equally good correlation has been established for the other atoms as well in the coordination sphere of Pt.

The hydroformylation activity of various 5- and 6-membered P-heterocycles was investigated in platinum-catalysed hydroformylation of styrene. All of the tested ligands, such as the phosphole-, oxaphosphorine- and phoshinine-based ligands proved to be catalytically active. Especially good aldehyde selectivities were obtained with the chelating diphenylphosphino- tetrahydrophosphinine and diphenylphosphino-hexahydrophosphinine ligands. While the two aldehyde regioisomers were formed close to equimolar amounts with the monodentate ligands, high branched selectivities were observed with the chelating ones. The effect of the 4-substitution of the parent styrene on chemo- and regioselectivity was investigated.

Racemic and optically active 1-propyl- and 1-butyl-3-methyl-3-phospholene oxides, as well as 1-propyl-3-methylphospholane oxides were converted after deoxygenation to the corresponding phosphine-borane and phopshine-platinum complexes. Stereostructure of the novel platinum complexes with a propyl group on the phosphorus atom was evaluated by quantum chemical calculations. The complexes displayed characteristic properties regarding their NMR spectra and showed unusual regioselectivity as catalysts in the hydroformylation of styrene derivatives. Ee-s up to 21% were obtained in the presence of optically active Pt-complex precursors.

3-Diphenylphosphinoyl-1-phenylphospholane 1-oxide (2) obtained by the Michael addition of diphenylphosphine oxide to the double-bond of 1-phenyl-2-phospholene 1-oxide (1) was subjected to double deoxygenation to afford the corresponding bisphosphine (3, LuPhos) that was converted to bis(phosphine borane) 4 and to cis chelate platinum(II) complex 6. A mixed phosphine oxide-phosphine borane 5 was also prepared. Stereostructures of the bidentate P-ligand 3 and the ring platinum(II) complex (6) were evaluated by quantum chemical calculations. Complex 6 used as a catalyst showed modest activity, but unusual regioselectivity in the hydroformylation of styrene and its 4-substituted analogues.

A new triphenylphosphane based on a β-cyclodextrin skeleton (PM-β-CD-OTPP) was synthesized. This ligand can be dispersed in water by using the nanoprecipitation method. Transmission electron microscopy and NMR spectroscopy showed that PM-β-CD-OTPP is aggregated in water and forms a stable dispersion. Its aqueous solubility can be dramatically increased in the presence of selected water-soluble guests by formation of inclusion complexes. Associated to a rhodium precursor, PM-β-CD-OTPP is able to generate soluble rhodium species in water. In addition, NMR experiments showed that the cyclodextrin cavity remains accessible for a guest even when PM-β-CD-OTPP is coordinated to rhodium. Finally, this ligand was efficient for rhodium-catalyzed hydrogenation and hydroformylation performed in aqueous medium.

Syntheses of 4-acetoxy-2,6-disubstituted tetrahydropyrans via Prins cyclisation of homoallylic alcohols with benzylic aldehydes are described and the methodology is applied in the total synthesis of diarylheptanoid 1 confirming both the structure and abso

By using a heterobimetallic catalyst, (CO)4(PEtPh 2)-W(μ-PPh2)Rh(CO)(PPh3), chemoselective hydroformylation of monosubstituted alkenes proceeds efficiently at room temperature under atmospheric pressure of CO/H

Hydroformylation of alkenes can be carried out in a few minutes under microwave activation at a relatively low pressure (40 psi) using commercially available catalysts and ligands. The 80 mL vial of a Discover microwave oven was connected to a cylinder of CO and H2, and after filling the reactor at 40 psi, a mixture of an alkene, the Wilkinson catalyst, and XANTPHOS was submitted to microwave irradiation giving, after 4 min, high conversion into the corresponding aldehyde without formation of the isomerized alkene.

Solvent free biphasic hydroformylation of various water-insoluble terminal olefins can be achieved in high yields and selectivities by using a water-soluble rhodium/triphenylphosphine trisulfonate catalyst and per(2,6-di-o-methyl)-β-cyclodextrin as inverse phase transfer catalyst. The catalytic activities were up to ten times higher than those observed without per(2,6-di-o-methyl)-β-cyclodextrin.