Palladium-catalyzed carboxylative cyclization of α-allenyl amines in dense carbon dioxide

Carboxylative transformation of 2,3-allenic amines into 5-vinyl-1,3-oxazolidin-2-ones was promoted by palladium catalysts under a pressurized CO₂ condition. The presence of a stereogenic center adjacent to the allene group resulted in the formation of the corresponding cyclic urethane as a single trans-diastereomer.     

Synthesis, complexation behavior and application of a new diphosphite ligand in rhodium-catalyzed hydroformylation

Oxidative coupling of 3-(3-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester (2) gave dimethyl 3,3′-(5,5′-di-tert-butyl-6,6′-dihydroxybiphenyl-3,3′-diyl)-dipropionate (1c), which upon phosphorylation/transesterification with a phosphochloridite derived from (R)-binaphthol, formed the new unsymmetrical binaphthol-bridged diphosphite 4. A rhodium catalyst based on 4 as ligand gave predominantly iso-selectivity in the hydroformylation of selected styrenes but opposite regioselectivity with 2,6-disubstituted derivatives. New chelate metal complexes (acac)RhL, PdCl₂L and PtCl₂L have been synthesized by reacting 4 with (acac)Rh(CO)₂, PdCl₂(MeCN)₂ and PtCl₂(COD), respectively. The structure of obtained compounds is determined based on ¹H, ¹³C, ³¹P and ¹⁹⁵Pt NMR spectroscopy and mass spectrometry data.     

铑(Ⅰ)/三-H_8-联萘单齿亚磷酸酯高效催化双环戊二烯氢甲酰化制备双醛（英文）

双环戊二烯(DCPD)是石脑油和燃料油裂解蒸汽的C5馏分中最重要的组分之一.DCPD经氢甲酰化反应可转化为具有广泛应用前景的三环癸烷不饱和单甲醛(TCDMA)和三环癸烷二甲醛(TCDDA),并可通过还原或胺化进一步转化为相应的醇和胺类化合物,用于农药、医药、润滑油和香料等的合成.但是,由于其分子结构中含有3,4-位和8,9-位两种不同活性的不饱和双键,因此DCPD氢甲酰化反应的产物通常非常复杂.过去数十年,研究者们为此相继开发了高转化率和高选择性的催化体系.但是反应条件相对都比较苛刻,尤其是对于双醛TCDDA的合成,通常需要较高的反应温度和反应压力以及大量的催化剂.本文以2'-联萘位置含有不同酯取代基(OCOMe,OCOPh,OCOAdamantyl和OCOPhCl)的三-H8-联萘单齿亚磷酸酯L1-L4为配体,以不同价态的金属铑前驱体为催化剂,开发了Rh催化DCPD氢甲酰化反应的新体系,并对亚磷酸酯配体、不同价态的金属铑催化剂前驱体、反应温度、反应时间、溶剂以及不同的底物和催化剂的S/C摩尔比对DCPD转化率和TCDDA选择性的影响进行了深入的研究.结果表明,当以金属铑前驱体Rh(acac)(CO)_2和配体L4-OCOPhCl为催化体系时,在DCPD氢甲酰化反应中表现出很高的活性,尤其是当S/C=4000时,TON值达到3286,并且该催化体系对于双醛TCDDA具有良好的选择性.值得注意的是,在相对温和的条件(6 MPa,120℃)下,Rh(Ⅰ)催化剂与氯苯酯基取代的三-H_8-联萘单齿亚磷酸酯所形成的配合物在催化DCPD的氢甲酰化反应中,DCPD的转化率达到99.9%,而双醛TCDDA的选择性达到98.7%.此外,我们采用L4-OCOPhCl作为模型单齿磷酸配体,在溶液中通过NMR对可能形成的Rh(Ⅰ)/亚磷酸酯催化物种进行了深入的考察.~(13)P NMR谱图表明,在DCPD的氢甲酰化反应中,催化物种[Rh(acac)(CO)(L4-OCOPhCl)]比[Rh(acac)(CO)(L2-OCOPh)]具有更好的稳定性,而且只有体积较大的配体L4-OCOPhCl才能与铑前驱体Rh(acac)(CO)_2进行很好的配位.     

Novel α-fluorinated cyclic phosphite and phosphinite ligands and their Rh-complexes as suitable catalysts in hydroformylation

Asymmetrical cyclic phosphite and phosphinite ligands of a novel type bearing either trifluoromethyl or pentafluorophenyl group were synthesized using >PCl or >PN< species and racemic fluorinated alcohols. The P-ligands were converted to complexes of Rh^III(L)(Cp^∗)Cl₂ type (where L = phosphite or phosphinite) and, in two instances, their stereostructures were evaluated by X-ray analysis. These complexes along with in situ systems, formed from Rh(CO)₂(acac) precursor and the corresponding ligand, were tested in the hydroformylation of styrene. Both systems provided excellent hydroformylation activities at 100 °C. Using the Rh^I in situ systems, moderate and high regioselectivities towards the branched aldehyde (2-phenyl-propanal) were obtained at 100 and 40 °C, respectively.     

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.     

Pyrazoles as ligands for the Rh-catalyzed hydroformylation of alkenes in supercritical carbon dioxide

Activity of pyrazole ligands in hydroformylation of a number of unsaturated terminal substrates in supercritical carbon dioxide (scCO₂) in the presence of Rh-catalyst was studied. The ligands without free NH group at position 1 of the pyrazole ring were found to be active. The use of scCO₂ as the reaction medium served to reach a higher conversion and regioselectivity of hydroformylation as compared to those in toluene.     

Ruthenium-catalyzed addition of carboxylic acids or cyclic 1,3-dicarbonyl compounds to propargyl alcohols

Monomeric ruthenium(0) complexes containing redox-coupled dienone ligands were found to catalyze the regio-selective addition of carboxylic acids or cyclic 1,3-dicarbonyl compounds to propargyl alcohols.     

Comparison of a range of rhodium-based catalysts for the hydroformylation of selected alkenes

Four rhodium-based catalyst systems 1, 2, 3, and [Rh(OAc)₂]₂/PPh₃ have been used in the hydroformylation of 1-hexene, styrene and some phosphino-, amino- and amido-alkenes. In general the catalysts showed very similar reactivity and selectivity.     

Rhodium-tris(3,5-bis(trifluoromethyl)phenyl)phosphine catalyzed hydroformylation of dienes to dialdehydes in supercritical carbon dioxide with high activity

Rhodium-catalyzed hydroformylation of 1,5-hexadiene and 1,7-octadiene to corresponding dialdehydes was investigated in compressed CO₂ and in toluene using different fluorinated phosphine compounds as ligands. A rhodium complex using tris(3,5-bis(trifluoromethyl)phenyl)phosphine is highly effective in compressed CO₂ for double hydroformylation of 1,5-hexadiene, whose TOF value is much larger than those reported so far. It has been shown that this ligand is effective also for the hydroformylation of 1,7-octadiene and scCO₂ is a better solvent than a conventional organic solvent of toluene for the title reaction.     

α-Fluorinated cyclic amidophosphite ligands. Their synthesis, Rh complexes and catalytic activity in the hydroformylation of styrene

The synthetic approaches to cyclic phosphite and amido(diamido)phosphite ligands bearing the residues of electron withdrawing perfluorinated tails at the β-position to the phosphorus atom have been elaborated. Catalytic systems based on rhodium complexes of these ligands formed in situ using Rh(CO)₂(acac) as a catalytic precursor demonstrate high activity in the hydroformylation of styrene along with good selectivity in respect to branched aldehyde. Quantum-chemical calculations proved that both the rate of the formation of branched alkyl complex, as well as its reactivity are influenced by the steric and electronic parameters in the same manner.     

New mono- and bidentate P-ligands using one-pot click-chemistry: synthesis and application in Rh-catalyzed hydroformylation

Three families of new phosphorus ligands have been prepared using the click-chemistry approach proceeding in only two steps and without intermediate P-protection. The methodology allows the high yield production of mono- and bidentate P-ligands, bearing at least one P–O bond. The ligands were tested in the Rh-catalyzed hydroformylation of 1-octene.     

Protic metal-containing ionic liquids as catalysts: Cooperative effects between anion and cation

HCo(CO)₄ is known to be the active species in the cobalt-catalyzed hydroformylation reaction. Although it is known that the anion [Co(CO)₄]⁻ is catalytically inactive, some cobalt carbonyl-containing ionic liquids are surprisingly able to catalyze hydroformylation reactions. However, only ionic liquids with protic cations demonstrate activity, whilst aprotic cations such as BMIM⁺ result in a completely inactive compound. The four applied cobalt-containing ionic liquids differ only by the cation component. Their different performance in catalytic activity allows the presumption of cooperative effects between the cation and the anion. These fundamental influences of the cation on the hydroformylation kinetics give hints for the reaction mechanism of biphasic hydroformylation reactions as well as on the reaction pathways of the conventional hydroformylation reaction under different reaction conditions.     

Regioselective hydroaminomethylation of 1,1-diaryl-allyl-alcohols: a new access to 4,4-diarylbutylamines

Pharmacologically active 4,4-diarylbutylamines like Fluspirilene and 4-amino-1,1-diarylbutan-1-ols like Difenidol were prepared in high yields via rhodium catalysed hydroaminomethylation of 1,1-diaryl-allylalcohols. Conversion of these olefins with carbon monoxide, hydrogen and secondary amines proceeds with complete regioselectivity. This group can easily be removed under acidic and hydrogenating conditions, enabling the transformation of 4-amino-1,1-diarylbutan-1-ols to 4,4-diarylbutylamines in high yields. Thus Fluspirilene was synthesised in 88% yield in four steps starting from commercially available materials.     

Arene ruthenium oxinato complexes: Synthesis, molecular structure and catalytic activity for the hydrogenation of carbon dioxide in aqueous solution

Two families of arene ruthenium oxinato complexes of the types [(η⁶-arene)Ru(η²-N,O-L)Cl] and [(η⁶-arene)Ru(η²-N,O-L)(OH₂)]⁺ have been synthesized from the dinuclear precursors [(η⁶-arene)RuCl₂]₂ (arene = para-cymeme or hexamethylbenzene) and the corresponding oxine LH (LH = 8-hydroxyquinoline, 5-chloro-8-hydroxyquinoline, 5,7-dichloro-8-hydroxyquinoline, 5-nitro-8-hydroxyquinoline, 5,7-dimethyl-8-hydroxyquinoline, 5,7-dichloro-2-methyl-8-hydroxyquinoline). The molecular structures of the neutral chloro complexes [(η⁶-C₆Me₆)Ru(η²-N,O-L)Cl] (LH = 8-hydroxyquinoline, 5,7-dichloro-2-methyl-8-hydroxyquinoline) and [(η⁶-MeC₆H₄Prⁱ)Ru(η²-N,O-L)Cl] (LH = 5,7-dichloro-2-methyl-8-hydroxyquinoline) as well as those of the cationic aqua derivatives [(η⁶-MeC₆H₄Prⁱ)Ru(η²-N,O-L)(OH₂)]⁺ (LH = 8-hydroxyquinoline, 5,7-dimethyl-8-hydroxyquinoline), isolated as the tetrafluoroborate salts, show in all cases a piano-stool arrangement with the arene ligand, the chelating oxinato ligand and the chloro or the aqua ligand surrounding the ruthenium center in a pseudo-tetrahedral fashion. The analogous reaction of [(η⁶-MeC₆H₄Prⁱ)RuCl₂]₂ with other N,O-chelating ligands such as 2-pyridinemethanol or tetrahydrofurfurylamine did not give the expected analogs but resulted in the formation of the complexes [(η⁶-MeC₆H₄Prⁱ)Ru(η²-NC₅H₄CH₂OH)Cl]⁺ and [(η⁶-MeC₆H₄Prⁱ)Ru(η¹-NHCH₂C₄H₃O)Cl₂]. The neutral and cationic complexes of the types [(η⁶-arene)Ru(η²-N,O-L)Cl] and [(η⁶-arene)Ru(η²-N,O-L)(OH₂)]⁺ have been found to catalyze the hydrogenation of carbon dioxide to give formate in alkaline aqueous solution with catalytic turnovers up to 400.     

Aerobic oxidative dehydrogenation of benzyl alcohols to benzaldehydes by using a cyclometalated ruthenium catalyst

The ruthenium(III) complex bearing phenylpyridine as a cyclometalated ligand serves as an efficient catalyst for the aerobic oxidative dehydrogenation of benzyl alcohols to the corresponding benzaldehydes under mild conditions and for the one-pot synthesis of benzonitriles from benzyl alcohols with ammonia.     

Heterogeneous catalysts for cyclic carbonate synthesis from carbon dioxide and epoxides

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烯烃羰化—步制醇铑系催化新体系的研究

羰基铑催化剂由于其加氢性能较弱，在羰基化反应的研究中，通常仅作为烯烃氢甲酰化制醛的催化剂。产物中得不到醇。本文则报道了以Ｒｈ＿２（ＡｃＯ）＿４和Ｒｈ＿６（ＣＯ）＿１６为催化剂，在一个反应器内进行烯烃氢甲酰化，加氢制醇的研究。系统考察了Ｒｈ／Ｐｂｕ＿３／ＥｔＯＨ催化体系受各种反应条件的影响。在最佳反应条件下，烯烃转化率达１００％。对醇选择性亦在９９．５％以上，正异构比在２以上．为烯烃一步制醇建立了铑系催化新体系。文中并利用红外光谱测定了反应过程的催化剂物种．实验证明，由烯烃一步制醇是由烯烃首先进行氢甲酰化反应，然后由生成的醛进一步加氢成醇的一个串联反应过程。前一步骤反应速度较快，２ｈ内可使９５％以上的烯烃转化为醛，后面由醛加氢成醇则进行缓慢，在１００—１２０℃下，至少２２ｈ，才能使醛全部转化为醇。     

Electrochemical carboxylation with carbon dioxide

Studies carried out in the past two years on electrochemical fixation of carbon dioxide with carbon-carbon bond formation, so-called electrochemical carboxylation or electrocarboxylation, are reviewed. Among about twenty papers on electrochemical carboxylation published from 2014 to the present, recent advances in electrochemical carboxylation regarding asymmetric carboxylation, sacrificial anode-free carboxylation, and carboxylation following aryl radical cyclization are focused on and discussed.