Hydroformylation of vinylsilanes with Rh(acac)(CO)2/tris(N-pyrrolyl)phosphine catalytic system

Rh(acac)(CO)₂ as catalyst precursor with a small excess of free N-pyrrolylphosphine ([P(NC₄H₄)₃]:[Rh] = 3–10) was found to be very active in hydroformylation of vinyltrisubstituted silanes at 80 °C and 10 atm CO/H₂ = 1. After 2 h the yields of aldehydes were 80 % (n/iso = 8) for vinyltrimethylsilane, 100 % (only n-isomer) for vinyldimethylphenylsilane and 95 % (n/iso = 5.5) for vinyltrimethoxysilane. The rate of hydroformylation of vinyltrimethylsilane is ca. three times higher than that of other vinylsilanes. 3,3-Dimethyl-1-butene undergoes hydroformylation much slower than vinyltrimethylsilane probably because of its high steric hindrance and the reaction produces 4,4-dimethylpentanal as the only product.     

A highly regioselective hydroformylation of an α-chiral olefin to produce a versatile trifunctionalised orthogonally protected C5 synthon

This paper describes a highly regioselective hydroformylation of (R)-N-phthalimido-vinylglycinol, [(R)-PVG]. By judicious choice of the reaction conditions, catalyst-controlled preferential formation of the linear regioisomer could be achieved in excellent yield. The hydroformylation product cyclised to a hemi-acetal, which is an orthogonally protected trifunctionalised enantio-enriched C5 synthon. The value of this versatile intermediate was demonstrated by the ready formation of enantio-enriched amino-diols, diamino-alcohols and differentially protected (R)-3-aminopiperidine.     

Rhodium/tris-binaphthyl chiral monophosphite complexes: Efficient catalysts for the hydroformylation of disubstituted aryl olefins

A family of threefold symmetry phosphite ligands, P(O–BIN–OR)₃ (BIN = 2,2′-binaphthyl; R = Me, Bn, CHPh₂, 1-adamantyl), derived from enantiomerically pure (R)-BINOL, was developed. Cone angles within the range 240–270° were calculated for the phosphite ligands, using the computational PM6 Hamiltonian. Their rhodium complexes formed in situ showed remarkable catalytic activity in the hydroformylation of hindered phenylpropenes, under relatively mild reaction conditions, with full chemoselectivity for aldehydes, high regioselectivity, however with low enantioselectivity. The ether substituents at the ligand affected considerably the catalytic activity on the hydroformylation of 1,1- and 1,2-disubstituted aryl olefins. The kinetics of the hydroformylation of trans-1-phenyl-1-propene, using tris[(R)-2′-benzyloxy-1,1′-binaphthyl-2-yl]phosphite as model ligand, was investigated. A first order dependence in the hydroformylation initial rate with respect to substrate and catalyst concentrations was found, as well as a positive order with respect to the partial pressure of H₂, and a slightly negative order with respect to phosphite concentration and CO partial pressure.     

Platinum-alkyl-B(C6F5)3 (or BF3) ‘in situ’ systems as tin(II) halide-free enantioselective hydroformylation catalysts

The dialkyl/diaryl-platinum complexes (Pt(CH₃)₂(bdpp); PtPh₂(bdpp) and Pt(2-Thioph)₂(bdpp), where bdpp stands for (2S,4S)-2,4-bis(diphenylphosphino)pentane) were reacted either with B(C₆F₅)₃, BPh₃ or BF₃. In the presence of PPh₃ or carbon monoxide cationic species with a general formulae [PtR(L)(bdpp)]⁺ (L = PPh₃, CO) were formed exclusively. The ability of boron additives to provide vacant coordination site at the platinum made these systems suitable as hydroformylation catalysts. Enantioselective hydroformylation of styrene was carried out in the presence of in situ catalysts formed from Pt(alkyl/aryl)₂(bdpp) and B(C₆F₅)₃ or BF₃. Moderate e.e-s depending strongly on the structure of the catalytic precursor have been obtained. DFT/PCM calculations reveal an S_N2-type reaction mechanism for the alkyl/aryl ligand abstraction with a notably lower activation barrier for BF₃.     

Hydroformylation activity of multinuclear rhodium complexes coordinated to dendritic iminopyridyl and iminophosphine scaffolds

The synthesis of poly(propyleneimine)-iminopyridyl and iminophosphine rhodium(I) metallodendrimers, with rhodium coordinated to monodentate (N-donor) and chelating, heterobidentate (P,N) moieties respectively located on the periphery, has been accomplished in order to evaluate their potential as hydroformylation catalysts. Related mononuclear complexes were obtained in a similar manner to model the multinuclear complexes. The multinuclear rhodium(I) complexes were found to be effective catalyst precursors in the hydroformylation of 1-octene, achieving higher conversions, faster reaction rates and slightly enhanced catalytic activity when compared with analogous mononuclear rhodium complexes. Hydroformylation reactions using the tetra- and octanuclear rhodium complexes generally show a chemoselective formation of aldehydes, together with a small amount of isomerisation products.     

Low pressure,highly active rhodium catalyst for the homogeneous hydroformylation of olefins

Hex-1-ene hydroformylation was examined at pressures of 1–11 atm and 40 °C, using Rh(acac)[P(OPh)₃]₂ + P(OPh)₃ as catalyst. The highest efficiency of aldehydes was achieved employing a small P(OPh₃)₃ excess-[P(OPh)₃]:[Rh] = 2:1. For reactions carried out at 1 atm, very high n/iso ratios i.e. 10–80 were obtained. Pressure increase caused a systematic drop of the n/iso ratio to ca. 5 at 11 atm. Simultaneously with hydroformylation, isomerisation of hex-1-ene to hex-2-ene occurs, but the contribution of the latter declines with increasing pressure. IR examination of the reaction mixture revealed that HRh(CO)[P(OPh)₃]₃ was the active form of the catalyst.The same catalytic system was applied in propylene hydroformylation at 5–10 atm pressure and 40 °C. In such conditions the yield of aldehydes was 10–70%, with a n/iso selectivity of 2–10.     

Ru3(CO)12/1,10-phenanthroline-catalyzed hydroformylation of styrene and acrylic esters

The Ru₃(CO)₁₂/1,10-phenanthroline-catalyzed hydroformylation of styrene under 100 atm of syngas (CO:H₂=1:1) at 120°C in DMF gives the corresponding branched and linear aldehydes in 58 and 22% yields, respectively. With the use of quinuclidine as a ligand in place of 1,10-phenanthroline in N,N-dimethylacetamide, the corresponding branched and linear oxo-alcohols were obtained in 53 and 28% yields, respectively. Hydroformylation of methyl acrylate by a catalyst system of Ru₃(CO)₁₂/1,10-phenanthroline to afford 4-methoxy-4-methyl-δ-valerolactone 1 in 31% yield, while the catalyst system of Ru₃(CO)₁₂/PPh₃ yields the open-chain aldehyde, dimethyl 2-formyl-2-methylglutarate (3), which is the precursor of lactone 1 in 18% yield.     

Intramolecular phosphine-directed hydroformylation. Application to the total synthesis of (+)-phyllanthocin

The temporary incorporation of a coordinating phosphine residue [m-(Ph₂P)C₆H₄CO] into the tetracyclic phyllanthocin precursor1a directed the [(COD)RhOAc]₂-catalyzed hydroformylation of1d largely to the desired C(3) position. This “intramolecular hydroformylation” strategy substantially improves a key transformation in the total synthesis of (+)-phyllanthocin.     

Control of chemo- and regio-selectivity in rhodium catalysed reactions of unsaturated amines with H2CO

The rhodium catalysed reactions of N-allyl- and N-butenyl-1,3-diaminopropanes give single products arising from exclusive hydroformylation at the terminal carbon when the hindered bisphosphite ligand, BIPHEPHOS is used. Reactions using a high carbon monoxide: hydrogen ratio (9:1) and triphenylphosphine as ligand give predominantly lactams arising from carbonylation but with poor control of regioselectivity.     

Catalysis by the Rh/B system Part 1. Vapour-phase hydroformylation of ethylene at atmospheric pressure on Rh/B on silica

A Rh/B system with rhodium crytallites of small dimensions was formed by reducing rhodium trichloride supported on silica with NaBH₄ atlow temperature. Thermal treatments in Ar and/or in CO/H₂ strongly modify the surface composition but induce only a small modification in the crystallite diameter. After treatment in Ar at 543 K and in CO/H₂ the Rh/B system catalyzes the vapor-phase hydroformylation of ethylene at atmospheric pressure in a flow reactor. The reaction proceeds with very good chemoselectivity toward the hydroformylation products (at 398 K, R is ⩾0.7). The formation of the catalytic species and the surface modifications were studied by X-Ray diffraction, FT—IR and XP spectroscopy. The presence of boron seems to play an important role both in preventing sintering of rhodium particles and in favouring good chemoselectivity toward the hydroformylation reaction.     

The mechanism of cleavage of 3-phenylallyl-silicon and -tin bonds by methanolic sodium methoxide

The distribution of deuterium in the hydroformylation products of ω-deuterated α-olefins is consistent with a reaction mechanism involving initial formation of an olefinic catalyst π-complex. The role of the intermediate complexes in the formation of the products in the hydroformylation of but-1-ene-4-d₃ has been evaluated.     

Xantphos as cis- and trans-chelating ligand in square-planar platinum(II) complexes. Hydroformylation of styrene with platinum-xantphos-tin(II)chloride system

Platinum(II) complexes of a diphosphine ligand xantphos (4,5-bis(diphenylphosphino)-9,9-dimethyl-xanthene) have been synthesised and characterised by NMR, conductivity and catalytic investigations. In addition to the parent complex cis-PtCl₂(xantphos), trans-platinum(II) complexes of square-planar geometry containing xantphos as a trans-chelating ligand can be obtained due to the large bite angle of the ligand. The platinum-xantphos-tin(II)chloride system acts as active hydroformylation catalyst in the hydroformylation of styrene resulting in high chemo- and regio-selectivities of up to 99.8% and 88%, respectively.     

Transformation of rhodium carbonyl complexes in hydroformylation of 1-hexene studied fromin situ IR spectroscopic data

Rhodium carbonyl complexes that formed from RhCl₃·4H₂O and RhCl₃·4H₂O modified by poly-N,N-dimethyl-N,N-diallylammonium chloride in a methanol—chloroform medium in the hydroformylation of 1-hexene were studied byin situ IR spectroscopy. Along with the rhodium hydrocarbonyl complexes, anionic complexes of the [Rh(CO)₂Cl₂]⁻ type, whose concentrations and rates of formation in an acidic medium are much higher than those in a basic medium, were shown to be the active centers of hydroformylation. The function of the polycation is the stabilization of the catalytically active mononuclear rhodium complexes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 708–710, April, 1999.     

A synthesis of 5-hydroxysedamine using hydroformylation

A synthesis of 5-hydroxysedamine, a Sedum alkaloid, has been completed using N,O-heterocycle chemistry to establish the aminoalcohol structure, hydroformylation to form the piperidine ring and diastereoselective dihydroxylation to introduce the 5-hydroxy group.     

Hydroformylation of alkenes with paraformaldehyde catalyzed by rhodium-phosphine complexes

The hydroformylation of medium-chain C6 olefins and of allyl alcohol was achieved with paraformaldehyde in dioxane solution using rhodium catalysts with mono-, bi-, and tri-dentate phosphine ligands. The highest activities with n/i ratios around 2, were obtained for a system derived from [Rh(dppe)₂]⁺, prepared in situ by reaction of Rh(acac)(CO)₂ with 2 eq of dppe.     

Rhodium-catalyzed hydroformylation of C6 alkenes and alkene mixtures - a comparative study in homogeneous and aqueous-biphasic media using PPh3, TPPTS and TPPMS ligands

The complexes RhH(CO)L₃, where L = PPh₃, P(m-C₆H₄SO₃Na)₃ (TPPTS), and (C₆H₅)₂P(m-C₆H₄SO₃Na) (TPPMS) were used as catalyst precursors for a comparative study of the catalytic hydroformylation of several C6 alkenes and alkene mixtures under moderate reaction conditions in homogeneous (PPh₃) and aqueous-biphasic (TPPTS, TPPMS) media. The biphasic systems are efficient for the hydroformylation of hex-1-ene, 2,3-dimethyl-1-butene, styrene, cyclohexene, and mixtures thereof, in water/n-heptane at 80 °C. The main problem associated with these catalysts is their tendency to promote alkene isomerization if the effective syngas concentration in the liquid phases is low, but this side-reaction can be suppressed by using higher CO/H₂ pressures (54 atm). The selectivity of both water-soluble catalysts for linear products of hex-1-ene and for branched products of styrene is modest in comparison with the homogeneous system, which may limit their utility for classical oxo uses, but this is not a disadvantage for other interesting applications related to the hydroformylation of alkene mixtures and particularly to naphtha upgrading where linear and branched products are equally useful. The catalysts can be recycled without significant loss of activity and are resistant to the presence of benzothiophene in the mixture.     

Hydroformylation of cyclic dienes catalysed by acetatocarbonylbis(triphenylphosphine)rhodium(I)

The hydroformylation of cyclic dienes in benzene using Rh(CO₂Me)(CO)(PPh₃)₂ as catalyst was studied. The formation of mono- or di-aldehydes was critically dependent on ring size, the smaller cyclic dienes favouring dihydroformylation. Intermediate alkene-aldehydes could be isolated under appropriate conditions, indicating that initial attack on the diene was by hydroformylation. Under hydroformylation conditions, these intermediates underwent either hydroformylation or hydrogenation, depending on the ring size. Linear dienes gave complex mixtures of products.     

Diastereoselective hydroformylation of acyclic olefins: Efficient construction of an all-anti stereotriade building block for polyketide synthesis

The hydroformylation of 2-phenyl-4-(prop-2-enyl)[1,3]dioxanes has been studied. anti-Acetals1a,b were found to give extraordinarily high diastereoselectivity on hydroformylation, giving rise to the formation of the all-anti stereotriades 2a,b. The origin of this stereoselectivity may be related to the preferred conformation of the actetals 3 in solution, as determined by 2D-NOESY NMR experiments and force field calculations (MM3). Hydroformylation of 1a afforded an intermediate for a short and efficient synthesis of a key building block for the total synthesis of the macrolide antibiotic bafilomycin A₁.     

N-Acetyl-N,N-dipyrid-2-yl (cyclooctadiene) rhodium (I) and iridium (I) complexes: Synthesis, X-ray structures, their use in hydroformylation and carbonyl hydrosilylation reactions and in the polymerization of diazocompounds

The synthesis of novel N-acetyl-N,N-dipyrid-2-yl complexes of Rh^I and Ir^I, i.e. [RhCl(CH₃CONPy₂)(COD)] (1) and [IrCl(CH₃CONPy₂)(COD)] (2), respectively, is described. Upon prolonged treatment in CH₂Cl₂ at room temperature, complex 1 is transformed into a cationic Rh-complex, i.e. [Rh(CH₃CONPy₂)(COD)⁺RhCl₂(COD)⁻] (1a). Compound 1a crystallizes in the monoclinic space group P2₁/c, complex 2 crystallizes in the triclinic space group . Compound 1 was investigated for its catalytic activity in the hydroformylation of cyclooctene as well as of 1-octene. In addition, 1 was used in various carbonyl hydrosilylation reactions of both aldehydes and ketones. There, turn-over numbers up to 50 000 and yields in the range of 85-100% were observed. Finally, compound 1 was successfully used for the polymerization of N₂CHCOOEt yielding highly stereoregular poly(ethoxycarbonylcarbene) with M_w = 67 000 g/mol and a polydispersity index (PDI) of 2.59.     

4-Indolylbutanals from rhodium-catalyzed hydroformylation of allylindoles as precursors of benzofused indolizines

New 4-indolylbutanals have been prepared via a rhodium-catalyzed hydroformylation of differently substituted N-allylindoles. The aldehydes bearing an electron-donating group on the indole nucleus 3-position can evolve into benzofused indolizines via a one pot intramolecular cyclodehydration.