Palladium phosphate

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Pd(Ph3P)2Cl2(Bu3SnH, benzene) or cobalt carbonyl. The palladium method cleaves allyl esters, propargyl phosphates, and propargyl carbamates as well. 

Bj Pivaloyloxymethyl D(—)-Ot-aminobenzylpenicillinate. hydrochloride To a solution of pivaloyloxymethyl D(—)-a-azidobenzylpenicillinate (prepared as described above) in ethyl acetate (75 ml) a 0.2 M phosphate buffer (pH 2.2) (75 ml) and 10% palladium on carbon catalyst (4 g) were added, and the mixture was shaken in a hydrogen atmosphere for 2 hours at room temperature. The catalyst was filtered off, washed with ethyl acetate (25 ml) and phosphate buffer (25 ml), and the phases of the filtrate were separated. The aqueous phase was washed with ether, neutralized (pH 6.5 to 7.0) with aqueoussodium bicarbonate, and extracted with ethyl acetate (2 X 75 ml). To the combined extracts, water (75 ml) was added, and the pH adjusted to 25 with 1 N hydrochloric acid. The aqueous layer was separated, the organic phase extracted with water (25 ml), and the combined extracts were washed with ether, and freeze-dried. The desired compound was obtained as a colorless, amorphous powder. 

Scheme 3) [30]. The pY + 3 diversity alcohols (Ri)-OI I (Fig. 15) were attached to the template through a Mitsunobu coupling to provide ether derivatives of 16. Palladium-mediated Alloc deprotection followed by amide formation using the phosphate-ester-containing diversity acids (R2)-C02H provided the fully coupled resin-bound products of 17. Cleavage from the resin with 95% TFA/H20, which also afforded benzyl phosphate deprotection, followed by reversed-phase (RP) semipreparative... 

C. 4-(3-Cyclohexenyl)-2-phenylthio-1-butene. To the above solution of the borane derivative, 0.809 g (0.700 mmol) of tetrakis(triphenylphosphine)palladium(0) (Note 9), 1.47 g (5.60 mmol) of triphenylphosphine (Note 10), 35 mL of 3 M potassium phosphate in water (Note 11), and finally 15.1 g (70.0 mmol) of 1-bromo-1-phenylthioethene are added and the resulting mixture is heated at reflux for 3 hr with stirring. The light brown solution is cooled to room temperature and treated with 6.4 g... 

The use of a lipophilic zinc(II) macrocycle complex, 1-hexadecyl-1,4,7,10-tetraazacyclododecane, to catalyze hydrolysis of lipophilic esters, both phosphate and carboxy (425), links this Section to the previous Section. Here, and in studies of the catalysis of hydrolysis of 4-nitrophenyl acetate by the Zn2+ and Co2+ complexes of tris(4,5-di-n-propyl-2 -imidazolyl)phosphine (426) and of a phosphate triester, a phos-phonate diester, and O-isopropyl methylfluorophosphonate (Sarin) by [Cu(A(A(A/,-trimethyl-A/,-tetradecylethylenediamine)l (427), various micellar effects have been brought into play. Catalysis of carboxylic ester hydrolysis is more effectively catalyzed by A"-methylimidazole-functionalized gold nanoparticles than by micellar catalysis (428). Other reports on mechanisms of metal-assisted carboxy ester hydrolyses deal with copper(II) (429), zinc(II) (430,431), and palladium(II) (432). 

Aryloxytitanium halides, 25 83 2-Arylpyridines, 27 111 Aryl phosphate esters, 79 51 Aryl phosphates, 7 7 493 Aryl phosphonates, 79 37 Arylphosphorus compounds, 79 28 Aryls, palladium, 79 652 Aryl-silicon compounds, 22 553, 554 Arylsulfinic acids, 27 248-249 Arylsulfonylated gelatin, 72 444 Aryltin trihalides, 24 810-811 Arylyl amines, 70 396-399 Asahi Chemical Industries EHD processes, 9 676-677 sebacic acid production, 9 679-680 ASAM (alkaline-sulfite-AQ-methanol) process, 27 30... 

Mikami and Yoshida extended the scope of this method considerably by using propargyl phosphates and chiral proton sources [94], The propargylic phosphates thereby have been found to be advantageous owing to their high reactivity towards palladium and the extremely low nudeophilicity of the phosphate group [95]. In some cases, it was even possible to obtain allenes from primary substrates, e.g. ester 194 (Scheme 2.60) [96]. A notable application of this transformation is the synthesis of the allenic isocarbacydin derivative 197 from its precursor 196 [97]. 

Scheme 2.60 Palladium-catalyzed reduction of propargylic phosphates with Sml2. TBS = Si(tBu)Me2.

Palladium-catalyzed reduction of propargyl acetates is possible with Sml2 in the presence of a proton source (Scheme 3.17) [51]. The allene/alkyne selectivity is greatly influenced by the choice of the proton source. Propargyl phosphates were also converted into hydridoallenes by Pd-catalyzed reduction with Sml2 [52],... 

The allenyl carboxylate 35 was obtained in an enantiomerically enriched form by the palladium-catalyzed reduction of the racemic phosphate 34 using a chiral proton source [53]. The two enantiomers of the (allenyl)samarium(III) intermediate are in rapid equilibrium and thus dynamic kinetic resolution was achieved for the asymmetric preparation of (i )-35 (Scheme 3.18). 

Scheme 4.70 Palladium-catalyzed asymmetric alkylation of 2,3-alkadienyl phosphates 273.

In another reduction, the propargylic phosphate 64 is reduced with samarium(II) iodide in the presence of tetrakis(triphenylphosphine)palladium and tert-butanol as a proton source the allene 65 is produced almost exclusively, <1% of the isomeric alkyne 66 being present in the product mixture [19]. 

Cyanohydrin diethyl phosphates 87, easily accessible from propargyl aldehydes or ketones of type 86, reacted with lithium dialkylcuprates or similar reagents via an Sn2 process to give cyanoallenes in moderate to good yields [135]. The transformations 80 —> 81 and 84 —> 85 are only formally also SN2 reactions. Thus, plausible catalytic cycles, which include different short-lived palladium intermediates, have been postulated to explain these nucleophilic substitution reactions [127, 134],... 

If allenes bear a potential leaving group in the a-position to the cumulene system, they are very attractive substrates for palladium-catalyzed substitutions. Examples are a-allenic acetates and particularly a-allenic phosphates, which react under palladium(O) catalysis with carbanions derived from /3-diesters, /i-keto esters, a-phenylsulfonyl esters and glycine ester derivatives. They lead to /3-functionalized allenes such as 86, 89 and 93 (Eqs. 14.9-14.11) [45 18]. 

Based on these reactions, Imada et al. reported the first enantioselective alkylation of 2,3-alkadienyl phosphates 96 by employing malonate derivatives 97 in the presence of palladium complex catalysts bearing MeOBIPHEP or BINAP as ligand (Scheme 14.21) [49]. The highest enantioselectivity (90% ee) was obtained by the catalyst combination Pd2(dba)3-CHC13 and (R)-MeOBIPHEP. 

As described in many reviews, Trost and his co-workers have carried out a pioneering work on the molybdenum-and tungsten-catalyzed allylic alkylation of allylic esters regioselectivity of the reaction is often complementary to the palladium-catalyzed allylic alkylation. The first asymmetric version was disclosed by Pfaltz and Lloyd-Jones in 1995 (Equation (63)). They used a catalytic amount of a novel tungsten complex, prepared from [W(CO)3(MeCN)3] or [W(cycloheptatriene) (COIs] and optically active (diphenylphosphino)phenyloxazolines 57, for the allylic alkylation of 3-aryl-2-propenyl phosphate with dimethyl sodiomalonate to isolate the corresponding branched alkylated compounds as a major isomer with an excellent enantioselectivity (96% ee). Unexpectedly, 3-aryl-2-propenyl carbonates are shown to be unreactive. It is worth noting that an isostructural molybdenum complex does not promote the catalytic alkylation under the same reaction conditions. In contrast, Lloyd-Jones and Lehmann reported the stereocontrolled... 

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