Meso-Epoxide ring opening catalyzed

Carree, F. Gil, R. Collin, J. (2004) Samarium iodides catalyzed meso-epoxides ring opening by aromatic amines.. Tetrahedron Lett., 45 7749-7751. 

Nakajima, M. Saito, M. Uemura, M. Hashimoto, S. (2002) Enantioselective ring opening of meso-epoxides with tetrachlorosilane catalyzed by chiral bipyridine N,N -dioxide derivatives.. Tetrahedron Lett., 43 8827-8829. 

Schaus, S. E. Jacobsen, E. N. (2000) Asymmetric ring opening of meso- epoxides with TMSCN catalyzed by (pybox)lanthanide complexes., Org. Lett, 2 1001-1004. 

The first example of asymmetric catalytic ring-opening of epoxides with sp2-hybridized carbon-centered nucleophiles was reported by Oguni, who demonstrated that phenyllithium and a chiral Schiff base ligand undergo reaction to form a stable system that can be used to catalyze the enantioselective addition of phenyllithium to meso-epoxides (Scheme 7.24) [48]. Oguni proposed that phenyllithium... 

Using the catalytic system described above, the enantioselective opening of meso epoxides could also be pursued. Although many excellent examples of ring-opening of meso epoxides by Sn2 reactions have recently been reported, the reaction planned here is conceptually different [40]. In the SN2 reaction, the path of the incoming nucleophile has to be controlled. In the titanocene-catalyzed reaction, the intermediate radical has to be formed selectively. If an intermediate similar to that invoked in the Bartmann ring-open-... 

Reymond, S. Brunei, J. M. Buono, G. (2000) New development in the enantioselective ring opening of meso-epoxides by various ion silicon sources catalyzed by an o-methoxyaryldiazaphosphonamide Lewis base., Tetrahedron Asymmetry, 11 4441-4445. 

Tokuoka, E. Kotani, S. Matsimaga, H. Ishizuka, T. Hashimoto, S. Nakajima, M. (2005) Asymmetric ring opening of meso-epoxides catalyzed by the chiral phosphine oxide BINAPO., Tetrahedron Asymmetry 16 2391-2392. 

Kureshy, R. 1. Singh, S. Khan, N. H. Abdi, S. H. R. Agrawal, S. Mayani, V. J. Jasra, R. V. (2006) Microwave-assisted asymmetric ring opening of meso-epoxides with aromatic amines catalyzed by a Ti-S-(—)-BlNOL complex.. Tetrahedron Lett., 47 5277- 5279. 

Ogawa, C. Azoulay, S. Kobayashi, S. (2005) Bismuth triflate-chiral bipyridine complex catalyzed asymmetric ring opening reactions of meso-epoxide in water., Heterocycles, 66 201-206. 

Gao, B. Wen, Y. Yang, Z. Huang, X. Liu, X. Feng X. (2008) Asymmetric ring opening of meso-Epoxides with aromatic amines catalyzed by a new proline-based N,N -dioxide-indium tris (triflate) complex,/t/v. Synth. Catal, 350 385- 390. 

Next to the above presented use of SiCl for the in situ preparation of a Lewis acid catalyst with a Lewis base for the aldol reaction, it is possible to apply this compound as a reagent in the ring opening of epoxides leading to chlorinated alcohols. Denmark [104] reported that the chiral phosphoramide 38 catalyzed the asymmetric ring opening reaction of meso-epoxides in the presence of tetrachlo-rosilane. Similar examples were provided by Hashimoto in 2002 [105], applying the A -oxide 39 as catalyst (Scheme 30). 

Chiral Bi(OTf)3-Catalyzed Asymmetric Ring-Opening Reactions of meso-Epoxides... 

Table 3 Bi-catalyzed asymmetric ring opening of meso-epoxide in water and organic solvents...

Buono, Gerard (2001). On the Beneficial Effect of ortho-Methoxy Groups in the Asymmetric Ring Opening of meso Epoxides with Silicon Tetrachloride Catalyzed by Chiralortho-Methoxyphenyldiazaphosphonamide Lewis Bases. Angewandte Chemie, International Edition in English. 40 4536. 

Tridentate Schiff base chromium(III) complexes were identified as the optimal catalysts for the enantioselective ring opening of meso-aziridines by TMSN3.51 Indeed, preliminary studies have shown that, although the (salen)chromium complexes catalyzed the reaction to some extent, they consistently led to low enantioselectivities (<14% ee). It was rationalized that the diminished reactivity and selectivity of the salen complexes with aziridines compared to epoxides was a result of the steric hindrance created by the /V-substituent of the coordinated aziridine. As expected, improved results were observed using tridentate ligands on the chromium center because they offer a less-hindered coordination environment (Figure 17.7).51... 

The effect of microwaves on the kinetics and the selectivity of the Cr (salen)-catalyzed asymmetric ring opening of epoxides was investigated by Dioos and Jacobs (2005). It was found that the reaction rate of the Cr (salen)-catalyzed kinetic resolution of terminal epoxides and the asymmetric ring opening (ARO) of meso-epoxides could be increased by three orders of magnitude without impairing the selectivity. 

A tridentate Schiff base Cr(III) complex derived from l-amino-2-indanol catalyzes the enantioselective ring opening of meso A-2,4-dinitrobenzyl aziridines with TMSN3 (Sch. 18) [96]. The chiral (salen)metal complexes, used in the enantioselective ring opening of epoxides, were found to be much less effective (for Cr) or inactive (for Co). 

Denmark et al. have extended this study to the enantioselective ring opening of meso-epoxides with silicon tetrachloride catalyzed by chiral phosphoramide 71 (Table 11). In this case, enantiomerically enriched chlorohydrins have been synthesized in enantiomeric excesses varying from 7 to 87 depending on the structure of the considered substrate [68]. 

Similar conditions have been applied to the ring-opening of meso epoxides using amines. Bismuth triflate catalyzes the reaction of cyclohexene oxide 64 with p-bromoaniline under aqueous conditions to provide the P-aminoalcohol 65 in 84% yield. In this particular case, the water solubility of the starting materials required the use of a micellar solution of sodium dodecyl sulfate (SDS) however, more soluble amines eould be employed in water and bismuth triflate alone <04TL49>. A lanthanide variant has also been reported. Thus, treatment of 64... 

Highly enantioselective catalytic desymmetrization of meso-epoxides through nucleophihc ring opening was first effectively demonstrated by Nugent, who found that a zirconium trialkanolamine complex catalyzed the addition of azi-dosilanes to meso-epoxides (Scheme 1) [3]. Azide has been the most widely explored nitrogen nucleophile [4,5,6,7], in part due to its utiHty as an amine sur-... 

Jacobsen reported that the Co(salen) complex 10 catalyzed the addition of carboxylic acids to meso-epoxides [20]. An initial screen revealed that benzoic acid and its derivatives were the most useful nucleophiles from the perspective of reactivity and selectivity. Although optical purities exceeding 90% ee were observed only with selected substrates, the crystalHnity of the benzoate esters in some cases allowed enhancement of their enantiopurity by recrystallization. The ring opening of cyclohexene oxide, for instance, proceeded on a multigram scale in quantitative yield and 77% ee subsequent recrystallizations of the monobenzoate ester 11 then afforded 98% ee material isolated in 75% yield (Scheme 7). 

Catalysts formed from Me2Zn and binaphthol 3.7 (R = H) have been used for asymmetric ene-reactions [778]. Enantioselective ring opening of meso-epoxides by n-BuSH is catalyzed by a potassium tartrate/ZnCl2 complex [559, 778, 805]. Mukaiyama and coworkers have shown that reaction of Et2Zn with chiral sulfamides 3.15 (R = PI1CH2, r-Pr) generates Lewis acids [806] that catalyze asymmetric reactions of aldehydes with ketene acetals. 

The use of zirconium complexes derived from tartramides 3.19 in asymmetric epoxidation of homoallylic alcohols does not result in any improvement over the related to titanium analogs [808]. A zirconium complex prepared from Zr(Otert-Bu)4 and (S,S,S)-triisopropylam3ne 3.22 in the presence of water catalyzes the asymmetric ring opening of meso-epoxides by /-PiMe2SiN3 (ee 85%), while related titanium complexes are less efficient [805,831]. 

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