Palladium propane

Reaction of the cyclopropyl-substituted pivalate (25) with dimethyl benzylidenema-lonate in the presence of a palladium catalyst gave a mixture of alkylidenecyclo-propane (26) and vinylcyclopropane (27). The ratio of these two adducts is found to be quite sensitive to the choice of ligand and solvent. While triisopropyl phosphite favors the formation of the methylenecyclopropane (26), this selectivity is completely reversed with the use of the bidentate phosphite ligand dptp (12). Interestingly there was no evidence for any products that would have derived from the ring opening of the cyclopropyl-TMM intermediate (Scheme 2.8) [18]. 

Compound A, C H O, was found to be an optically active alcohol. Despite its apparent unsaturation, no hydrogen was absorbed on catalytic reduction over a palladium catalyst. On treatment of A with dilute sulfuric acid, dehydration occurred and an optically inactive alkene B, Q iH14, was produced as the major product. Alkene B, on ozonolysis, gave two products. One product was identified as propanal, CH3CH2CHO. Compound C, the other product, was shown to be a ketone, CgHgO. How many degrees of unsaturation does A have Write the reactions, and identify A, B, and C. 

Figure 4. Comparison of Propane Aromatization Performances of a Palladium Membrane Reactor (PMR) and a Conventional Reactor (CR) using a Ga-H-ZSM-5 Catalyst...

Recently, Y. Yamamoto reported a palladium-catalyzed hydroalkoxylation of methylene cyclopropanes (Scheme 6-25) [105]. Curiously, the catalysis proceeds under very specific conditions, i.e. only a 1 2 mixture of [Pd(PPh3)4] and P(o-tolyl)3 leads to an active system. Other combinations using Pd(0 or II) precursors with P(o-tolyl)3 or l,3-bis(diphenylphosphino)propane, the use of [Pd(PPh3)4] without P(o-tolyl)3 or with other phosphine ligands were all inefficient for the hydroalkoxylation. The authors assumed a mechanism in which oxidative addition of the alcohol to a Pd(0) center yields a hydrido(alkoxo) complex which is subsequently involved in hydropal-ladation of methylenecyclopropane. 

Reduction of 2,2-bisf3 -nltro-4 -(4"-phenylsulfonylphenoxyl)phenyl1 propane. Compound 9, 200 mg (0.55 meg) was dissolved in a mixture of 30 mL of dichloromethane (DCM) and 30 mL of methanol and 240 mg of 10% palladium on charcoal was added. After purging the solution with argon for 30 min, 520 mg (13.6 mmol) of sodium borohydride was added portionwise over 10 min. The reaction mixture was stirred under argon for 1 hr before addition of 30 mL of DCM. The mixture was filtered, the filtrate evaporated, and the residue extracted with DCM. Evaporation of the extract yielded 140 mg (76.2%) of 2,2-... 

In the homodinuclear complex [ Pd(dppp) 2(//-biim)](OTf)2 (dppp = bis(diphenylphosphino)-propane, biim = 2,2 -biimidazole, 0Tf=0S02CF3) a biim2 ligand spans the two palladium(II) centers.535... 

Figure 53 Cationic 1,3-bis(diphenylphosphino)propane (dppp) palladium(II) complex.

Vinyl and Aryl Halides and Triflates. The organosilane reduction of aryl halides is possible in high yields with triethylsilane and palladium chloride.195 The reaction is equally successful with aryl chlorides, bromides, and iodides. Aryl bromides and iodides, but not chlorides, are reduced with PMHS/Pd(PPh3)4 in moderate to excellent yields.199 This system also reduces vinyl bromides.199 p-Chlorobenzophenone is reduced to benzophenone with yym-tetramethyldisilo-xane and Ni/C in excellent yield (Eq. 59).200 There is a report of the organosilane reduction of aryl and vinyl triflates in very high yields with the combination of Et3SiH/Pd(OAc)2/dppp (l,3-bis(diphenylphosphino)propane) (Eq. 60).201... 

A palladium phosphine complex [e.g., BCPE = l,2-bis(l,5-cyclooctylenephos-phino)ethane] was also reported to produce propanediols and n-propanol from glycerol at 443 K under 6 MPa CO/H2 atmosphere in acidic conditions, n-Propanol is the dominant product, while a slight preference for the formation of propane-1,3-diol is seen in the diol fraction. Reactions were performed at different temperatures in the range 413-448 K. Since acrolein was monitored at high temperature, a reaction network was proposed following a sequential dehydration/hydrogenation pathway [20]. 

In a similar study, Zhang and Wang (1997) studied the reaction of zero-valent iron powder and palladium-coated iron particles with trichloroethylene and PCBs. In the batch scale experiments, 50 mL of 20 mg/L trichloroethylene solution and 1.0 g of iron or palladium-coated iron were placed into a 50 mL vial. The vial was placed on a rotary shaker (30 rpm) at room temperature. Trichloroethylene was completely degraded by palladium/commercial iron powders (<2 h), by nanoscale iron powder (<1.7 h), and nanoscale palladium/iron bimetallic powders (<30 min). Degradation products included ethane, ethylene, propane, propene, butane, butene, and pentane. The investigators concluded that nanoscale iron powder was more reactive than commercial iron powders due to the high specific surface area and less surface area of the iron oxide layer. In addition, air-dried nanoscale iron powder was not effective in the dechlorination process because of the formation of iron oxide. 

The palladium-phosphine-catalyzed cycloaddition reactions of vinyloxetanes 530 with aryl isocyanates or diaryl-carbodiimides led to 4-vinyl-l,3-oxazin-2-ones 531 or l,3-oxazin-2-imines 532, respectively (Scheme 101). In the absence of phosphine ligands (PPhs, bis(diphenylphosphino)ethane (DPPE), l,3-bis(diphenylphosphino)propane (dppp), no conversion of heterocumulenes was observed. Starting from fused-bicyclic vinyloxetanes, both types of cycloadditions proceeded in a highly stereoselective fashion, affording only the r-isomers of alicycle-condensed 1,3-oxazine derivatives <1999JOC4152>. 

In Gegenwart von Palladium-Schwarz reagiert Azetidin bei 120-170° mit der 3fachen molekularen Menge an 1,2-Diamino-ethan, 1,3-Diamino-propan oder Bis-[3-amino-pro-pyl]-amin unter Ringoffnung durch Umalkylierung (vgl. S. 1214f.) zu 1,4,8-Triaza-octan (70%), 1,5,9-Triaza-nonan (73%) bzw. 1,5,9,13-Tetraaza-tridecan (75%)1. 

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