Camphor derivatives complexes with

Recently, another cobalt(II)/camphor-derived complex was developed for performing the asymmetric cyclopropanation of olefins [38]. The complex 18 was prepared by reacting the ligand 17, synthesized by condensation of (lR)-3-hydroxymethylenebornane-2-thione and the corresponding diamine, with co-balt(II) dichloride hexahydrate in degassed ethanol (Scheme 11). The cyclopropane derivatives were obtained in 50-60% yield using 3 mol % of the catalyst 18 and ethyl diazoacetate in styrene or 1-octene as solvent. The diastereomeric ratios were low for both styrene and 1-octene. 

MeLi to cyclohexenone with p-amino sulfide ligand 88-9 MeMgl to acyclic enone with arene-thiolatocopper(l) complexes 90-1 mesylamide ligand (camphor-derived) 174, 176... 

It is also possible to carry out a substrate-controlled reaction with aldehydes in an asymmetric way by starting with an acetylene bearing an optically active ester group, as shown in Eq. 9.8 [22]. The titanium—acetylene complexes derived from silyl propiolates having a camphor-derived auxiliary react with aldehydes with excellent diastereoselectivity. The reaction thus offers a convenient entry to optically active Baylis—Hillman-type allyl alcohols bearing a substituent (3 to the acrylate group, which have hitherto proved difficult to prepare by the Baylis—Hillman reaction itself. 

The auxihary acrylates 161 and 162 have been used in 1,3-dipolar cycloadditions with nitrile oxides. The camphor-derived acrylate 161 underwent a 1,3-dipolar cycloaddition with benzonitrile oxide with up to 56% de (Scheme 12.51) (263). The auxiliary in acrylate 162 is derived from naturally occurring L-quebrachitol, and provided an effective shielding of the re-face of the alkene in the reaction with benzonitrile oxide, as 90% de was obtained (273). Compound 163 was used in a reaction with the nitrone 1-pyrrole-1-oxide, and the reaction proceeded to give a complex mixture of products (274). 

Sato and coworkers have reported an asymmetric synthesis of Baylis-Hillman-type allylic alcohols 48, 49 via a chiral acetylenic ester titanium alkoxide complex (Scheme 9) [41]. These reactions rely on the use of the novel acetylenic ester titanium alkoxide complex 44 with a camphor-derived chiral auxiliary. Optically active, stereodefined hydroxy acrylates 46, 47 were obtained in high yields and with excellent regio- and diastereoselectivities. The chiral auxiliary was subsequently cleaved off by alcoholysis. 

A camphor-derived 1,3-diketonate complex 338c worked well (55-80% yield), but no asymmetric induction was observed. One-pot reactions to access 1,2,4-trioxanes were also effective using the new catalysts. Dussault and coworkers used 319 to catalyze the silyl peroxidation of 3-methyl-3-butenol in ethanol in 45% yield (entry 8) [386]. Some silylation of the alcohol function was also found under the reaction conditions. Similar double silyl peroxidation reactions were performed with trisub-stituted olefins in 52-78% yield using 319 as the catalyst [387]. 

A-Aminophthalimide (118) can also be added to olefins in an asymmetric fashion. Thus, reaction of A -enoyl oxazolidinone 122 with 118 and lead tetraacetate in the presence of the camphor-derived chiral ligand 120 provides aziridine 123 in 83% yield and with 95% ee <020L1107>. Other useful chiral ligands include imine 121, derived from the condensation of 2,2 -diamino-6,6 -dimethylbiphenyl with 2,6-dichlorobenzaldehyde. The corresponding monometallic Cu(I) complex was found to be very efficient in chiral nitrogen transfer onto chromene derivative 124 using (Ar-(p-toluenesulfonyl)imino)phenyliodinane (PhI=NTs) to provide aziridine 125 in 87% yield and 99% ee <02JOC3450>. 

Lanthanide /3-diketonates containing fluorinated chiral camphor-derived ligands (61, M = Pr, Eu, Er, Yb, R = Mef, n-Prf) form highly coordinated 14 complexes with zwitterionic, unprotected phenylalanine, leucine, and other amino acids under neutral conditions. This allows extraction of the amino acids from their neutral aqueous solutions into dichloromethane phases . 

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]. 

The bis-Cp dichloro titanium complex with the camphor-substituted Gp ring (Scheme 479) is prepared from the corresponding cyclopentadiene compound by reaction with LiBu11, metallating with TiCl3 followed by oxidation with HCl/air. From the initially formed 9 1 mixture of Cz- and Gi-symmetric bis-Gp derivatives, the pure U2-diastereomer... 

In subsequent investigations, in which solutions of salts the cations of which form complexes with unsaturated organic compounds were used as stationary phases, palladium and platinum derivatives were suggested [76]. Dicarbonylrhodium j3-diketonates show more interesting selectivity relative to olefins [77, 78]. Of the series of the rhodium compounds investigated, the best selectivity was shown by Rh(CO)2(3-trifluoroacetyl-camphorate) (1) [144—149] ... 

Picolinic acid also accelerates the H2O2 oxidations but less efficiently than pyrazine-2-carboxylic acid. It has been demonstrated recendy that the vanadium complex with picolinic acid, VO(PA)2 , encapsulated into the NaY zeolite retains solution-like activity in the liquid-phase oxidation of hydrocarbons [16a], It is noteworthy that pyrazine-2-carboxylic acid accelerates the hydrocarbon oxidation catalyzed by CH3Re03 [25 b]. Employing a (+)-camphor derived pyrazine-2-carboxylic acid as a potential co-catalyst in the CHsReOj-catalyzed oxidation of methyl phenyl sulfide with urea-H202 adduct, the corresponding sulfoxide was obtained with an e.e. of 15% [16b]. 

Using camphor-derived chiral lithium amide 40, the tricarbonylchromium complexes of phenyl carbamates could be ortho-deprotonated with good levels... 

Relatively little has appeared in the past year on the synthesis and reactivity of the six membered, potentially aromatic, phosphinine ring system. A route to the first C2-asymmetric phosphinine (147), derived from (+ )-camphor, has been developed from the reaction of a pyrylium salt precursor with P(TMS)3. The chiral phosphinine is a crystalline, air-stable solid and forms complexes with metal ions, therefore having some potential as a ligand in homogeneous eatalysis." A pyrylium salt-P(TMS)3 final step was also used in the synthesis of a series of 2-(2 -halo)triarylphosphinines (148), subsequently shown to form a series of tungsten(0) and rhodium(I) complexes involving coordination of the phosphorus sp lone pair to the metal." Interest has continued in studies of the coordination chemistry of phosphabarrelenes, derived from the established reactions of phosphinines... 

Sato and co-workers have developed an elegant titanium alkoxide promoted MBH reaction between enantiopure acetylenic esters 262-264 (Figure 2.16) and aldehydes. A new chiral dimetallic species, the acetylenic ester titanium alkoxide complex with a camphor-derived auxiliary, enabled the preparation of p-trimethylsilylated MBH adducts 265 with high diastereoselectivity (Scheme 2.150). ... 

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