Catalysts bis-acetate

Figure 19.8 Scope of asymmetric oxidation of electron-deficient alkenes with bis-acetate catalyst 19.

The reaction of 2-fluoro-2,2-dinitroethanol (119) with divinylether (118) under different conditions gives three products, namely, the expected vinyl acetal (120) and the bis-acetal (121) from addition of one and two equivalents of 2-fluoro-2,2-dinitroethanol, respectively, and the vinyl ether (122), which results from franx-etherification of (118) with loss of acetaldehyde. Shackelford and co-workers found that by altering the nature of the Lewis acid catalyst and the reaction stoichiometry they were able to alter the distribution ratio of these products. 

Jorgensen and co-workers reported the asymmetric additions of a silyl ketene acetal to aldehydes (40) using the chiral bis-sulfonamide catalyst 27 [109]. Among the limited number of aldehydes examined, adducts were obtained in moderate to high yields (41-90%) and modest levels of ee (30-56% Table 6.44). The corresponding mono-sulfonamide catalyst was inactive under the reported conditions. 

For catalytic asymmetric aldol-type reactions, the transformation of the methylene compounds to a silyl enolate or a silyl ketene acetal was at one time necessary. Recently, the aldol reaction of aldehydes with non-modified ketones was realized by use of the lanthanum-Li3-trisf(/ )-bi-naphthoxidej catalyst 22 [18]. According to the proposed catalytic cycle, after abstraction of an a-proton from the ketone, the reaction between the lithium-enolate complex and the aldehyde... 

The enantioselective Henry reaction by using copper acetate-bis(oxazoline) catalyst is reported by Evans . ... 

In previous works [8,9], bimetallic Bi-Pd catalysts supported on activated carbon and characterized by various Bi/Pd molar ratios ((Pd+Bi)=10 wt.%) were prepared from the thermal degradation of Bi and Pd acetate-type precursors under nitrogen at 773 K. Because several binary Bi-Pd alloys were heavily suspected in the supported catalysts, three intermetallic compounds, Bi2Pd, BiPd and BiPda were also prepared from the same precursors, according to the same... 

In a previous work [13], we reported on the preparation of carbon-supported bimetallic Bi-Pd catalysts by the thermal degradation of Bi and Pd acetate-type precursors under nitrogen at 773 K and described their catalytic properties in glucose oxidation. The formation of various BixPdy alloys (BiPd, BiPds, Bi2Pds) or, at least, associations on the surface of these catalysts during the activation step was heavily suspected. Alloy formation in supported bimetallic Pd-based catalysts has been mentioned several times in the literature in die presence of other promoting elements, like Pb or Te [14-16] and is sometimes assumed as responsible for the deactivation of the catalysts. 

Racemic sec-alcohols (12.96) undergo acylation with acetic anhydride using the Fu catalyst (12.95) and achieving very good selectivity factors. Copper bis-oxazohne catalysts also provide high selectivities in the asymmetric benzoylation of trans-1,2-diols. ... 

Dioctyltin diisooctylthioglycollate catalyst, PU two-pack coatings Dibutyltin bis (laurylmercaptide) catalyst, PU elastomers Ferric acetylacetonate N-Hydroxyethy I pi perazi ne catalyst, purified terephthalic acid polyesters Manganese acetate (ous) catalyst, PVC suspension polymerization Lauroyl peroxide catalyst, pyridine synthesis Cobaltocene... 

Poole and Dhanesar investigated the thallium(i)-catalysed electrophilic bromination of diphenyl ether and l,3-bis(3-pheno)yphenoxy)benzene in their study of the preparation of cyanophenyl ethers that could be used as polar and thermally stable liquid phases in gas chromatography. Under mild conditions, bromination of diphenyl ether with thallium(i) acetate catalyst produces exclusively the para-substituted product. Formation of ortho- and para-substituted products could be achieved under more vigorous conditions, such as higher temperature and increased concentration of bromine and thallium(i) salts (Scheme 20.22). Similarly, the substitution pattern of l,3-bis(3-pheno)yphenoxy)benzene bromination product could be controlled by reaction conditions. 

As in the case of C-H insertion, Si-H bond functionalization in aryl- and vinyl-diazoacetates takes place in the presence of dirhodium catalysts, and chiral ones result in asymmetric induction [60a]. In pioneering studies by Doyle et al, enantioselective Si-H bond insertion with chiral dirhodium catalysts was achieved [90]. Recently, Ball etal reported innovative studies with bis-acetate dirhodium complexes, bearing chelating nona-peptides (see Section 9.2.3.2), which catalyzed the enantioselective carbenoid insertion into Si-H bonds (Scheme 9.18) [46]. The optimization of the peptide bound to the dirhodium unit or the presence of a phosphite additive significandy improved the enantiose-lectivity of the silane products [46]. 

When allylic compounds are treated with Pd(0) catalyst in the absence of any nucleophile, 1,4-elimination is a sole reaction path, as shown by 492, and conjugated dienes are formed as a mixture of E and Z isomers[329]. From terminal allylic compounds, terminal conjugated dienes are formed. The reaction has been applied to the syntheses of a pheromone, 12-acetoxy-1,3-dode-cadiene (493)[330], ambergris fragrance[331], and aklavinone[332]. Selective elimination of the acetate of the cyanohydrin 494 derived from 2-nonenal is a key reaction for the formation of the 1,3-diene unit in pellitorine (495)[333], Facile aromatization occurs by bis-elimination of the l,4-diacetoxy-2-cyclohex-ene 496[334],... 

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]. 

N-2-cyanoethylaniline has been prepared (accompanied by much of the N,N -bis-2-cyanoethyl compound) by heating aniline, acrylonitrile and acetic acid either in an autoclave, or at refluxing temperature for 10 hours in the presence of various inorganic catalysts. The substance has also been obtained, free of the N,N -bis-2-cyanoethyl compound, from aniline salts and /3-diethylaminopropionitrile. ... 

Just as selective oxidation can be carried out on these systems, reduction also occurs with considerable selectively. Hydrogenation of binaphthol (Pd catalyst) in glacial acetic acid at room temperature for seven days affords the octahydro (bis-tetrahydro) derivative in 92% yield with no apparent loss of optical activity when the reaction is conducted on optically pure material. The binaphthol may then be converted into the bis-binaphthyl crown in the usual fashion. 

A rhodium-on-alumina catalyst deactivated in bis-(4-aminophenyl)-methane saturation (I IS C, 100 psig) was regenerated by two washings with aqueous ammonia at 65°C, followed by drying at 90°C(I6) or by washing with acetic acid. 

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