Phosphines conversion

Phosphine Conversion Time Product/reduction Product/double Yield... 

Phosphine Conversion Time Product/Reduction Yield" 1 pph. 

Dimerization is the main path. However, trimerization to form 1.3,6,10-dodecatetraene (15) takes place with certain Pd complexes in the absence of a phosphine ligand. The reaction in benzene at 50 C using 7r-allylpalladium acetate as a catalyst yielded 1,3,6,10-dodecatetraene (15) with a selectivity of 79% at a conversion of 30% based on butadiene in 22 h[ 19,20]. 1,3,7-Octatriene (7) is dimerized to 1,5,7,10.15-hexadecapentaene (16) with 70% selectivity by using bis-rr-allylpalladium. On the other hand. 9-allyl-l,4,6.12-tridecatetraene (17) is formed as the main product when PI13P is added in a 1 1. ratio[21]. 

Rhodium Ca.ta.lysts. Rhodium carbonyl catalysts for olefin hydroformylation are more active than cobalt carbonyls and can be appHed at lower temperatures and pressures (14). Rhodium hydrocarbonyl [75506-18-2] HRh(CO)4, results in lower -butyraldehyde [123-72-8] to isobutyraldehyde [78-84-2] ratios from propylene [115-07-17, C H, than does cobalt hydrocarbonyl, ie, 50/50 vs 80/20. Ligand-modified rhodium catalysts, HRh(CO)2L2 or HRh(CO)L2, afford /iso-ratios as high as 92/8 the ligand is generally a tertiary phosphine. The rhodium catalyst process was developed joindy by Union Carbide Chemicals, Johnson-Matthey, and Davy Powergas and has been Hcensed to several companies. It is particulady suited to propylene conversion to -butyraldehyde for 2-ethylhexanol production in that by-product isobutyraldehyde is minimized. 

Dimerization is reportedly catalyzed by pyridine [110-86-1] and phosphines. Trialkylphosphines have been shown to catalyze the conversion of dimer iato trimer upon prolonged standing (2,57). Pyridines and other basic catalysts are less selective because the required iacrease ia temperature causes trimerization to compete with dimerization. The gradual conversion of dimer to trimer ia the catalyzed dimerization reaction can be explained by the assumption of equiUbria between dimer and polar catalyst—dimer iatermediates. The polar iatermediates react with excess isocyanate to yield trimer. Factors, such as charge stabilization ia the polar iatermediate and its lifetime or steric requirement, are reported to be important. For these reasons, it is not currently feasible to predict the efficiency of dimer formation given a particular catalyst. 

Garbodiimide Formation. Carbodiimide formation has commercial significance in the manufacture of Hquid MDI. Heating of MDI in the presence of catalytic amounts of phosphine oxides or alkyl phosphates leads to partial conversion of isocyanate into carbodiimide (95). The carbodiimide (39) species reacts with excess isocyanate to form a 2 + 2cycloaddition product. The presence of this product in MDI leads to a melting point depression and thus a mixture which is Hquid at room temperature. 

The reaction of methyl propionate and formaldehyde in the gas phase proceeds with reasonable selectivity to MMA and MAA (ca 90%), but with conversions of only 30%. A variety of catalysts such as V—Sb on siUca-alumina (109), P—Zr, Al, boron oxide (110), and supported Fe—P (111) have been used. Methjial (dimethoxymethane) or methanol itself may be used in place of formaldehyde and often result in improved yields. Methyl propionate may be prepared in excellent yield by the reaction of ethylene and carbon monoxide in methanol over a mthenium acetylacetonate catalyst or by utilizing a palladium—phosphine ligand catalyst (112,113). 

In the presence of a large excess of PH, primary phosphines, RPH2, are formed predominantiy. Secondary phosphines, R2PH, must be either isolated from mixtures with primary and tertiary products or made in special multistep procedures. Certain secondary phosphines can be produced if steric factors preclude conversion to a tertiary product. Both primary and secondary phosphines can be substituted with olefins. After the proper selection of substituents, mixed phosphines of the type RRTH or RR R T can be made. 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

Conversion o( organic azides with phosphines or phosphites to Immophosphoranes (phosphazo compounds) and their hydrolysis to amines. 

Determine what size plug flow reactor, operating at 650°C and 5.0 atm, produces 85% conversion of the feed consisting of 4 kg/mols of pure phosphine per hour. 

In general, azides are more easily available than rutro compounds by S 2 reacnon of the corresponding halides Thus, the direct conversion of an azide mto a nitro group is useful for the synthesis of nitro compounds Corey and coworkers have reported the easy cc azides to nitro compounds via ozonolysis of phosphine irrunes fEq 2 70 ... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

The isomerization of an allylic amine to an enamine by means of a formal 1,3-hydrogen shift constitutes a relatively small structural change. However, this transformation could be extremely valuable if it could be rendered stereoselective. In important early studies, Otsuka and Tani showed that a chiral cobalt catalyst, prepared in situ from a Co(ii) salt, a chiral phosphine, and diisobutylaluminum hydride (Dibal-H), can bring about the conversion of certain pro-chiral olefins to chiral, isomeric olefins by double bond migra-... 

An alternative reported in the same publication involves the in situ conversion of the carboxylic acids to the corresponding acyl chlorides using PS-PPh3 and CCI3CN (THE, 10 °C, 5 min) before treatment with the amidoxime in the presence of DIEA (THE, 150 °C, 15 min). The resin-bound phosphine not interfering with the second step, and THF being the best solvent for both steps, the two-steps sequence could be performed one-pot with yields comparable to those obtained using the HBTU/PS-BEMP combination (Scheme 12). 

We discovered a complementary procedure for conversion of OMen to other functional groups. The ester P-OMen bond was shown to be cleaved in a stereoselective manner reductively [85,86]. The cleavage takes place with almost complete preservation of stereochemical integrity at phosphorus. The reducing agents are usually sodium or Hthium naphthalenide, lithium biphenyUde, and Hthium 4,4 -di-fert-butylbiphenyl (LDBB). The species produced is then quenched with an alkyl hahde or methanol to afford tertiary or secondary phosphines, respectively (Scheme 5b). Overall, the displacement reaction proceeds with retention of configuration. 

The enantioselective 1,4-addition addition of organometaUic reagents to a,p-unsaturated carbonyl compounds, the so-called Michael reaction, provides a powerful method for the synthesis of optically active compounds by carbon-carbon bond formation [129]. Therefore, symmetrical and unsymmetrical MiniPHOS phosphines were used for in situ preparation of copper-catalysts, and employed in an optimization study on Cu(I)-catalyzed Michael reactions of di-ethylzinc to a, -unsaturated ketones (Scheme 31) [29,30]. In most cases, complete conversion and good enantioselectivity were obtained and no 1,2-addition product was detected, showing complete regioselectivity. Of interest, the enantioselectivity observed using Cu(I) directly in place of Cu(II) allowed enhanced enantioselectivity, implying that the chiral environment of the Cu(I) complex produced by in situ reduction of Cu(II) may be less selective than the one with preformed Cu(I). 

A number of NH phosphinous amides have been P-alkylated by previous conversion to their corresponding anions [59,74]. A particular case of double alkylation takes place with the anion derived from the AT-phosphino phosphinous amide NH(PPh2)2 yielding the diphosphonium salt 17 [102] (Scheme 17). When neutral, its methylation is reported to give the P-H phosphazene-phos-phonium salt 18 [103]. 

Hydroformylation is an important industrial process carried out using rhodium phosphine or cobalt carbonyl catalysts. The major industrial process using the rhodium catalyst is hydroformylation of propene with synthesis gas (potentially obtainable from a renewable resource, see Chapter 6). The product, butyraldehyde, is formed as a mixture of n- and iso- isomers the n-isomer is the most desired product, being used for conversion to butanol via hydrogenation) and 2-ethylhexanol via aldol condensation and hydrogenation). Butanol is a valuable solvent in many surface coating formulations whilst 2-ethylhexanol is widely used in the production of phthalate plasticizers. 

The protocol of the allylic alkylation, which proceeds most likely via a c-allyl-Fe-intermediate, could be further improved by replacing the phosphine ligand with an M-heterocyclic carbene (NHC) (Scheme 21) [66]. The addition of a ferf-butyl-substituted NHC ligand 86 allowed for full conversion in the exact stoichiometric reaction between allyl carbonate and pronucleophile. Various C-nucleophiles were allylated in good to excellent regioselectivities conserving the 71 bond geometry of enantiomerically enriched ( )- and (Z)-carbonates 87. Even chirality and prochirality transfer was observed (Scheme 21) [67]. 

Two papers have appeared on the reactions of halogenophosphines with tervalent phosphorus compounds. In a detailed study of the reactions at 20 °C of a range of tertiary phosphines with phosphorus trichloride, dichlorophenylphosphine, and chlorodiphenylphosphine, it has been shown that, in general, 1 1 adducts are formed, provided that the tertiary phosphine is a good nucleophile. With diphenylchlorophosphine, for example, an adduct (18) is formed with dimethylphenylphosphine, but not with diphenylmethylphosphine, although the relative importance of steric and electronic factors remains to be established. The related reactions of phosphorus trichloride and of dichlorophenylphosphine are much more complex, and the initial crystalline products are not amenable to analysis. The reactions at 280 °C of a similar system have been shown to lead to halogen exchange, e.g. the conversion of (19) to (20). 

---