Synthesis chiral hydroperoxides

In this review, we focus mainly on the preparative utility of organic peroxides, and only few mechanistic investigations are discussed. This review covers synthetic methodologies for the preparation of alkyl hydroperoxides and dialkyl peroxides (Section II) and the synthetic use of these peroxides in organic chemistry (Section III). In Section II, general methods for the synthesis of organic hydroperoxides and dialkyl peroxides are discussed, as well as the preparation of enantiomerically pure chiral hydroperoxides. The latter have attracted considerable interest for asymmetric oxidation reactions during the last years. 

In the case of diastereomeric mixtures of chiral hydroperoxides, standard chromatography on achiral phase can be employed to separate the diastereomers. As one example for the preparation of optically pure hydroperoxides via this method, the ex-chiral pool synthesis of the pinane hydroperoxides 11 is presented by Hamann and coworkers . From (15 )-cw-pinane [(15 )-cw-10], two optically active pinane-2-hydroperoxides cA-lla and trans-llb were obtained by autoxidation according to Scheme 17. Autoxidation of (IR)-c -pinane [(17 )-cw-10] led to the formation of the two enantiomers ent-lla and ent-llh. The ratio of cis to trans products was 4/1. The diastereomers could be separated by flash chromatography to give optically pure compounds. 

Chiral endoperoxides, synthesis, 260, 261 Chiral hydroperoxides aUyhc alcohol asymmetric epoxidation, 401-6, 407-9... 

NMR spectroscopy, 694-5 vibrational spectra, 692 X-ray diffraction, 695-6 synthesis, 309-51 tertiary, 690-1 theoretical aspects, 67-84 thymine ozonolysis, 616 see also Chiral hydroperoxides DNA... 

Fu H, Kondo H, Ichikawa Y, Look GC, Wong C-H (1992) Chloroperoxidase-Catalyzed Asymmetric Synthesis Enantioselective Reactions of Chiral Hydroperoxides with Sulfides and Bromohydration of Glycals. J Org Chem 57 7265... 

Also of significant preparative potential is the kinetic resolution of chiral hydroperoxides in the presence of sulfides or guaiacol [253-261]. The reaction has been shown to occur with CPO, HRP and CiP and provides good to excellent results for a multitude of different substrates. Whereas usually the back-reaction of Compound I to the resting state is used for organic synthesis, Compound I is formed upon the stereoselective decomposition of alkylhydroperoxides here. Scheme 2.20 illustrates the first example described in the literature [253] where CPO and different aryl methyl sulfides have been employed and where it has been found that mainly the R-form of the chiral hydroperoxide is reduced to the corresponding alcohol. 

Di Riria, F., Modena, G. and Seraglia, R. (1984) Synthesis of chiral sulfoxides by metal-catalyzed oxidation with t-butyl hydroperoxide. Synthesis y25 y2JS. 

Di Furia, R, Modena, G. and Seragha, R. (1984). Synthesis of Chiral Sulfoxides by Metal-Catalyzed Oxidation with T-Butyl Hydroperoxide, Synthesis, 4, pp. 325—326. 

Hydroperoxides, as optically active oxidizing agents 289-291 Hydrosulphonylation 172 /J-Hydroxyacids 619 a-Hydroxyaldehydes, synthesis of 330 a-Hydroxyalkyl acrylates, chiral 329 j -Hydroxycarboxylic esters, chiral 329 3-Hydroxycycloalkenes, synthesis of 313 Hydroxycyclopentenones, synthesis of 310 -Hydroxyesters 619 synthesis of 616 Hydroxyketones 619, 636 Hydroxymethylation 767 a-Hydroxysulphones, synthesis of 176 / -Hydroxysulphones 638, 639 reactions of 637, 944 electrochemical 1036 synthesis of 636 y-Hydroxysulphones 627 synthesis of 783... 

Although it was also Henbest who reported as early as 1965 the first asymmetric epoxidation by using a chiral peracid, without doubt, one of the methods of enantioselective synthesis most frequently used in the past few years has been the "asymmetric epoxidation" reported in 1980 by K.B. Sharpless [3] which meets almost all the requirements for being an "ideal" reaction. That is to say, complete stereofacial selectivities are achieved under catalytic conditions and working at the multigram scale. The method, which is summarised in Fig. 10.1, involves the titanium (IV)-catalysed epoxidation of allylic alcohols in the presence of tartaric esters as chiral ligands. The reagents for this asyimnetric epoxidation of primary allylic alcohols are L-(+)- or D-(-)-diethyl (DET) or diisopropyl (DIPT) tartrate,27 titanium tetraisopropoxide and water free solutions of fert-butyl hydroperoxide. The natural and unnatural diethyl tartrates, as well as titanium tetraisopropoxide are commercially available, and the required water-free solution of tert-bnty hydroperoxide is easily prepared from the commercially available isooctane solutions. 

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