Tricyclohexylphosphine, reactions

The reaction of isoprcnc with Et NH in the presence of triethylammonium iodide (10 mol%) gives the 1 1 adducts 51 and 52 with high selectivity(53]. The reaction of isoprene with ammonia or diethylamine affords the tail-to-tail dimer 53 when Pdfacac) and (BuO)jP are used as the catalyst. The head-to-head dimer 54 is obtained with Pd(acac)2, BF,. and tricyclohexylphosphine(54]. 

Reaction of 3 with 1 equivalent of a phosphine results in formation of "phosphine-modified catalysts (4). The complex formed from 7r-allyl-nickel chloride, tricyclohexylphosphine, and methylaluminum dichloride (4a) has been isolated and its structure determined crystallographically (see Fig. 1) (57) The phosphine is bonded to the nickel atom, and interaction with the Lewis acid takes place via a chlorine bridge. The bridging chlorine atom is almost symmetrically bound to both the nickel... 

Very subtle ligand effects have been detected in these reactions. Thus, under the same conditions, 1 mole of tricyclohexylphosphine and 1 mole of Ni(COD)2 in the presence of excess morpholine catalyze addition of acetophenone to 2 moles of butadiene to give compound A below, whereas triphenylphosphine gives B. With triphenylphosphite C—C coupling no longer occurs, but morpholine adds to butadiene to give C (135). 

Moreover, the Nb complex hydrogenates catalytically aryl- and benzyl-substituted phosphine under similar conditions (Scheme 6.16) [149]. Kinetic studies show that the hydrogenation of triphenylphosphine into the monocyclohexyl, dicyclohexyl, and tricyclohexylphosphine are successive reactions, and the rate of hydrogenation of the arylphosphine decreases as the number of cyclohexyl substituents increases [153]. 

Normally, the oxidative addition of an aryl chloride to Pd(0) is reluctant to take place. But such a process is greatly accelerated in the presence of sterically hindered, electron-rich phosphine ligands [e.g., P(/-Bu)3 or tricyclohexylphosphine]. In late 1990s, Reetz [76] and Fu [77] successfully conducted intermolecular Heck reactions using arylchlorides as substrates, as exemplified by the conversion of p-chloroanisole to adduct 77 [77], The applications of this discovery will surely be reflected on future Heck reactions of non-activated heteroaryl chlorides. 

Pd-catalyzed double carbonylation reactions are rare due to the inefficiency of formation of bis-carbonylation products. Addition of bulky tricyclohexylphosphine to the normal carbonylation system greatly facilitated the formation of the double carbonylation product. Subjecting 4-iodopyridine 199 to such conditions afforded primarily 4-pyridylglyoxylic acid derivative 200, which was not easily attainable via classical synthetic methods [159]. The monoamide 201 was isolated as a minor by-product. 

The results of this analysis of the product and catalyst distribution show that only a limited range of systems may be apphcable for the telomeriza-tion of butadiene and carbon dioxide. The reaction was performed in the biphasic systems EC/2-octanol, EC/cyclohexane and EC/p-xylene. The yield of 5-lactone reached only 3% after a reaction time of 4 hours at 80 °C. hi the solvent system EC/2-octanol triphenylphosphine was used as the hgand. With the ligand bisadamantyl-n-butyl-phosphine even lower yields were achieved in a single-phase reaction in EC or in the biphasic system EC/cyclohexane. The use of tricyclohexylphosphine led to a similar result, only 1% of the desired product was obtained in the solvent system EC/p-xylene, which forms one homogeneous phase at the reaction temperature of 80 °C. Even at a higher temperature of 100 °C and a longer reaction time of 20 hours no improvement could be observed. Therefore, we turned our interest to another telomerization-type process. 

Significant advances in organonickel chemistry followed the discovery of frtzws,fraws,fraws-(l,5,9-cyclododecatriene)nickel, Ni(cdt), and bis(l,5-cycloocta-diene)nickel Ni(cod)2 by Wilke et. al.1 In these and related compounds, in which only olefinic ligands are bonded to the nickel, the metal is especially reactive both in the synthesis of other compounds and in catalytic behavior. Extension of this chemistry to palladium and to platinum has hitherto been inhibited by the lack of convenient synthetic routes to zero-valent complexes of these metals in which mono- or diolefins are the only ligands. Here we described the synthesis of bis(l,5-cyclooctadiene)platinum, tris(ethylene)-platinum, and bis(ethylene)(tricyclohexylphosphine)platinum. The compound Pt(cod)2 (cod = 1,5-cyclooctadiene) was first reported by Muller and Goser,2 who prepared it by the following reaction sequence ... 

To a 300 mL Hastelloy-B autoclave was added 31.0 mL (24.5 g, 765 mmol) of methanol, 90.0 mL (70.Og, 378 mmol) of tributyl amine, 33.0 mL (33.8 g, 251 mmol) of 1-chloropinacolone, 14.0 mg (0.019 mmol) of [(cyclohexyl)3P)]2PdCl2, and 28.0 mg (0.1 mmol) of tricyclohexylphosphine. The autoclave was sealed, flushed with carbon monoxide, and pressurized to 30 psi with CO. The autoclave was then heated to 120°C and the pressure was adjusted to 150 psi. The temperature and pressure were maintained using a continuous carbon monoxide feed for 3 h. The mixture was then cooled to yield a two phase reaction product. The entire product mixture (both layers) was diluted with 50.0 mL (39.55 g) of methanol to generate a homogeneous mixture and analyzed by gas chromatography. Variations in the procedure regarding temperature, pressure, catalyst levels (phosphine and Pd) are indicated in the tables and text. 

A 500-ml flask was charged with the step 2 product (0.105 mol), the step 3 product (0.245 mol), and 70 ml of toluene, and then stirred at ambient temperature. Thereafter the solution was treated with bis(2,4-pentanedionato)palladium (0.070 mmol) and tricyclohexylphosphine (0.070 mmol) dissolved in 10 ml of toluene and dimethylanilinium tetrakispentafluorophenyl borate (0.28 mmol) dissolved in 5 ml of CH2C12. The mixture was stirred at 80°C for 1 hour, during which time toluene was suitably added as the viscosity of the reaction solution increased. After the reaction was completed, the solution was diluted with toluene and the mixture precipitated in excess methanol. The precipitate was filtered off and washed with a large amount of methanol, the polymer dried in vacuo at 110°C for 6 hours, and 61.4 g of product isolated. 

A tetrahydrofuran (THF) (20 mL) solution of a mixture of 1.7 g (6.2 mmol) of bis(l,5-cyclooctadiene)nickel, Ni(cod)2, 1.7 g (6.2 mmol) of tricyclohexylphosphine, and 1.1 g (13 mmol) of 2-methyl-2-propenamide (methacrylamide) is stirred for 6 h at room temperature in a nitrogen-filled 50-mL Schlenk tube equipped with a magnetic stirring bar. A greenish-yellow precipitate results. The reaction mixture is cooled to — 30 °C, and after 2 h the solvent containing... 

The rate of polymerization can be controlled by a gel modification additive. A gel modification additive is a substance that cooperates with the catalyst to change the rate of the catalyzed reaction. Most generally, a gel modification additive may be any electron donor or Lewis base. Particularity suitable compounds acting in this way are tricyclohexylphosphine, tricyclopentylphosphine, triisopropyl-phosphine, triphenyl phosphine, and pyridine. 

Ruthenium complexes have been described that are active both in the ROMP reaction and in a subsequent hydrogenation step (30). These catalysts have the pyrimidin moiety incorporated, for example, (l,3-diisopropyltetrahydropyrimidin-2-ylidene) (ethoxy-methylene) (tricyclohexylphosphine) ruthenium dichloride. 

Reaction (21) occurs with cyclohexene and both cis- and trans-2-butene, without isomerization of the alkenes,139 while the reduction of Ni(acac)2 with Al(alkyl)3 in the presence of PCy3 and 2-butene (cis and trans) affords the complex bis(tricyclohexylphosphine)(l-butene)nickel(0)>... 

Sulfine complexes of platinum(II) can be formed by oxidative addition to Pt(PPh3)3. The initial step involves the formation of an rj2-CS complex which undergoes intramolecular oxidative addition of a C—S bond (equation 542).1869 Use of Pt(cod)2 and PCy3 gives the tricyclohexylphosphine analogue.1870 The reaction gives two stereoisomers.1871 The coordination stabilization of sulfines allows their synthesis in the coordination sphere of platinum, but the cyclic process is not very efficient.1872... 

Tris (triphenylphosphine) nickel, tris (tri-p-tolylphosphine) nickel, and bis (1,3-diphenylphosphinepropane) nickel proved to be good catalysts, the first being slightly more effective. The tricyclohexylphosphine complex was a very poor catalyst, and bis (cyclooctadiene) nickel did not catalyze cyanation. Cyanation of several substituted aromatic halides in the presence of Ni[P(C6H5)3]3 prepared by reducing dichlorobis (triphenylphosphine) nickel (II) 2 with a powdered manganese iron (80 20) alloy (Reaction 3) is reported in Table II. 

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