Nickel camphorate

Metal Complex. Complexation gas chromatography was first introduced by V. Schurig in 1980 (118) and employs transition metals (eg, nickel, cobalt, manganese or rhodium) complexed with chiral terpenoid ketoenolate ligands such as 3-ttifluoroacetyl-lR-camphorate (6),... 

Figure 1-18. Gas chromatographic separation of a) synthetic racemic dihydromanicone rac- 44 b) natural 44, obtained by hydrogenation of material from the heads of M. rubida c) co-injected natural-44 and rac-44 d) synthetic (4 5,65 )-44 and e) co-injected synthetic (4RS,6S)-44 and rac-44. Chiral GC phase nickel(II)-bis[3-heptafluorobutyryl-(lR)-camphorate]. Signals 1 and 4 correspond to the pair of diastereomers (4 5,65)-44 signals 2 and 3 correspond to (4RS,6R)-44. Reprinted, with permission, by VCH, Ref. 63.

In this special field, earlier work had been done in other laboratories, such as by the Schering Company, Berlin (36), and by Ipatieff (37) in connection with his work on the hydrogenation of camphor and of other organic compounds. At both places, the favorable effect of alkali oxides and earth alkali oxides on nickel, cobalt and copper has been investigated. Similarly, Paal and his coworkers (38) have used a palladium-aluminum hydroxide catalyst in 1913 for the hydrogenation of double bonds. Bedford and Erdman (39) had reported that the catalytic action of nickel oxide is enhanced by the oxides of aluminum, zirconium, titanium, calcium, lanthanum, and magnesium. 

Figure 13. Rapid simultaneous separation of eight stereoisomers (enantiomers and diastereomers) of 2-mcthyl-3-(l -methylpropyl)oxiranc on 0.125 M nickel(ll) bis[3-(heptafluorobutanoyl)-(l / )-camphorate] in SB-30 [20 m x 0.25 mm (i.d.) glass capillary column. 90 C. 1 bar nitrogen].

Figure 23. Top temperature-dependent reversal of enantioselectivity for the enantiomers of (1-methyleth-yl)oxirane by complexation gas chromatography on nickel(II) bis[3-(heptafluorobutanoyl)-8-methylene-(1 /i)-camphorate]203. Bottom linear Van t Hoff plot and determination of the isoenantioselectivc temperature (89 °C).

Camphor- 10-sulfonic acid, 62 Unsaturated acetals or ketals Nickel boride, 197 (2R,4R)-Pentanediol, 237 Acetylenic carbonyl compounds a,p-Unsaturated acetylenic carbonyl compounds... 

FIGURE 19 Effect of temperature on the chiral resolution of (a, c) 1-phenylethanol and (b, d) camphor on capillary containing the Chiralsil-nickel CSP (SFC). (From Ref. 94.)... 

The invertomers of the nitrogen pyramid 1-chloro-2,2-dimethylaziridine have been separated by enantioselective complexation GC on the chiral metal chelate nickel(II)-bis[(3-heptafluorobutanoyl)-( l.R>)-camphorate] (Ni-CAM2) in squalane (Schurig et al., 1979). The resolution of the chiral aziridine into two sharp peaks with a = 1.5 in 45 min at 60° C demonstrated the stereochemical integrity of the invertomers (cf. Figure 6). 

Tishchenko (79), using a modified form of Raney nickel, obtained a 95.7 % yield of camphor from the dehydrogenation of borneol. Rutovskii, (80) received a 93.5% yield of camphor with Raney alloy. Reeves and Adkins (81), studying the dehydrogenation of primary alcohols, removed the hydrogen with ethylene. It was found that, though Raney nickel could be used for a catalyst for the reaction, the yields were low and, in general, the Raney nickel was inferior to a catalyst composed of copper, zinc, nickel, and barium chromite. 

Graphene was prepared by four different methods, namely the reductive pyrolysis of camphor (CG), exfoliation of graphitic oxide (EG),4 conversion of nanodiamond (DG)5 and arc evaporation of SiC (SG).6 In the first method, to prepare CG, camphor was pyrolysed over nickel particles under a reducing atmosphere. The reaction was carried out in a two-stage furnace and camphor was slowly sublimed (170 °C) by heating from the first furnace to the second furnace held at 770 °C where the... 

Nin(bis(3-heptafluorobutanoyl)-10-methylene-(lR)-camphorate is termed Chirasil-Nickel, which attached to capillary surfaces or polydimethylsilane performs GC separations of chiral ligand mixtures at 170 to 180 °C,62,63 and may be adapted to the use of supercritical C02 solvent for separations of organometallics. 

The asymmetric conjugate addition of diethylzinc with chalcone was also catalyzed by nickel and cobalt complex (Eq. (12.31)) [71]. A catalytic process was achieved by using a combination of 17 mol% of an aminoalcohol 34 and nickel acetylacetonate in the reaction of diethylzinc and chalcone to provide the product in 90% ee [72, 73]. Proline-derived chiral diamine 35 was also effective, giving 82% ee [74]. Camphor-derived tridentate aminoalcohol 36 also catalyzes the conjugate addition reaction of diethylzinc in the presence of nickel acetylacetonate to afford the product in 83% ee [75]. Similarly, the ligand 37-cobalt acetylacetonate complex catalyzes the reaction to afford the product in 83% ee [76]. 

An enantioselective version of the cyclopentaannulation via [3 + 2] cycloaddition has been developed using cyclopent-2-enone and several different methylenecyclopropanes. Whereas chiral phosphane ligands, such as menthyldiphenylphosphane (21), or the camphor-derived sultam 22 only result in enantiomeric excesses of 31% at a maximum in nickel(0)-catalyzed reactions, the enantioselectivity dramatically increases when the bidentate azaphospholene ligand 23 is employed. The yields, however, are relatively low due to the competing formation of alkylation products. ... 

Tabun has a stereogenic (chiral) phosphoms atom and exists as a pair of enantiomers. A gas chromatograph study of the enantiomers of tabun has been reported (Degenhardt et al., 1986). Separation was achieved through the use of bis[(l/f)-3-(heptafluorobutyryl-camphorate)nickel(II). This approach also separated stereoisomers of both sarin and soman. These authors also reported the stereospecific hydrolysis of racemic tabun using phosphorylphosphatases. They noted the species (mouse, rat, horse) dependence of the hydrolysis. Dilute solutions of tabun in inert solvents (e.g., carbon tetrachloride) exhibit optical stability for months at — 25°C. 

The camphor-derived tridentate amino alcohol 32 (Scheme 17) also catalyzes the conjugate addition reaction of diethylzinc in the presence of nickel acetylac-etonate to afford the product in 83% ee [75]. Similarly the Hgand 33-cobalt acety-lacetonate complex catalyzes the reaction to afford the product in 83% ee [76]. 

The first applications of nickel-catalyzed [3 + 2] cycloaddition to asymmetric diastereose-lective synthesis of metbylenecyclopentanes employed acrylic ester substrates chirally modified with menthol-4 or camphor-derived41,42 auxiliaries. The adducts were obtained in good yield with diastereomeric ratios up to 99 141-42. After hydrolysis, optically active 3-methylene-l-cy-clopentanecarboxylic acids 4 were obtained. 

Figure 13.13 A, enantiomeric forms of 2, 2-dimethylchloroaziridine B, nickel (II) bis-3-heptafluorobutyryl-(IR)-camphorate C, resolution of mixture A on a 100 m capillary column coated with B dissolved in squalane.

Interesting examples of optical resolutions include the use of dicarbonyl-rhodium(i) 3-trifluoroacetyl-(li )-camphorate for g.l.c. separation of chiral olefins and of dimeric nickel(ll) bis-(3-trifluoroacetyl-li -camphorate) for an improved separation of chiral epoxides (cf. Vol. 8, p. 8). The resolution of (i /5)-pantoic acid with chiral amines derived from a- and jS-pinene (Vol. 7, p. 43, ref. 420) may signal their more widespread use. 1,3-Dithian 1-oxide has been resolved. ... 

Cartoni et al. [88] studied perspective of the use as stationary phases of n-nonyl- -diketonates of metals such as beryllium (m.p. 53°C), aluminium (m.p. 40°C), nickel (m.p. 48°C) and zinc (liquid at room temperature). These stationary phases show selective retention of alcohols. The retention increases from tertiary to primary alcohols. Alcohols are retained strongly on the beryllium and zinc chelates, but the greatest retention occurs on the nickel chelate. The high retention is due to the fact that the alcohols produce complexes with jS-diketonates of the above metals. Similar results were obtained with the use of di-2-ethylhexyl phosphates with zirconium, cobalt and thorium as stationary phases [89]. 6i et al. [153] used optically active copper(II) complexes as stationary phases for the separation of a-hydroxycarboxylic acid ester enantiomers. Schurig and Weber [158] used manganese(ll)—bis (3-heptafiuorobutyryl-li -camphorate) as a selective stationary phase for the resolution of racemic cycUc ethers by complexation GC. Picker and Sievers [157] proposed lanthanide metal chelates as selective complexing sorbents for GC. Suspensions of complexes in the liquid phase can also be used as stationary phases. Pecsok and Vary [90], for example, showed that suspensions of metal phthalocyanines (e.g., of iron) in a silicone fluid are able to react with volatile ligands. They were used for the separation of hexane-cyclohexane-pentanone and pentane-water-methanol mixtures. 

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