Diol from epoxide

From the standpoints of both cost and atom economy, water is the ideal nucleophile for synthesis of enantioenriched C2-symmetric 1,2-diols from meso-epoxides. 

An alternative method for generating enriched 1,2-diols from meso-epoxides consists of asymmetric copolymerization with carbon dioxide. Nozaki demonstrated that a zinc complex formed in situ from diethylzinc and diphenylprolinol catalyzed the copolymerization with cyclohexene oxide in high yield. Alkaline hydrolysis of the isotactic polymer then liberated the trans diol in 94% yield and 70% ee (Scheme 7.20) [40]. Coates later found that other zinc complexes such as 12 are also effective in forming isotactic polymers [41-42]. 

Scheme 3.42. Synthesis of cyclohexan-1,3-diols from epoxides containing a C=C-double bond.

Diols from Lithium P-Lithioalkoxides Generated by the Reductive Lithiation of Epoxides 2,5-Dimethyl-2,4-hexanediol. 

Figure 11. Synthesis of the chrysene 1,2- and 3,4-dihydrodiols and the corresponding diol epoxide derivatives from chrysene by Method III (50. Reagents (i) H2,Pd (ii) H2,Pt (iii) DDQ (iv) AgOBZ,I25 (v) NBS A.

Tumorigenicity of tetrahydroepoxides. As yet, only Ch H -epoxide has been directly demonstrated to be tumorigenic (18). However, indirect evidence has been found in the high tumorigenicity of 3,4-dihydro BA, 9,10-dihydro BeP and 3,4-dihydrobenz[c]acridine (19-21), each of which is a likely metabolic precursor of a bay-region H -epoxide. In the case of 9,10-dihydro BeP, cis- and trans-9,10-dihydroxy -9,10,11,12-tetrahydro BeP were identified as products of metabolism of 9,10-dihydro BeP (22), and are the expected products of hydration of the epoxide. Diols are also formed from 7,8-dihydro BaP upon metabolism with prostaglandin endoperoxide synthase (23) or with rat liver homogenates (24). 

The mutagenicities of the bay region diol epoxides derived from BA, BaAcr and BcAcr toward S. typhimurium strain TA 100 (similar results are obtained in strain TA 98) and Chinese hamster V79 cells... 

The asymmetric oxidation of organic compounds, especially the epoxidation, dihydroxylation, aminohydroxylation, aziridination, and related reactions have been extensively studied and found widespread applications in the asymmetric synthesis of many important compounds. Like many other asymmetric reactions discussed in other chapters of this book, oxidation systems have been developed and extended steadily over the years in order to attain high stereoselectivity. This chapter on oxidation is organized into several key topics. The first section covers the formation of epoxides from allylic alcohols or their derivatives and the corresponding ring-opening reactions of the thus formed 2,3-epoxy alcohols. The second part deals with dihydroxylation reactions, which can provide diols from olefins. The third section delineates the recently discovered aminohydroxylation of olefins. The fourth topic involves the oxidation of unfunc-tionalized olefins. The chapter ends with a discussion of the oxidation of eno-lates and asymmetric aziridination reactions. 

DNA binds and reacts with carcinogenic and similar compounds which alkylate it through cationic intermediates, in some cases extraordinarily fast 1371 and can in the process catalyse the hydrolysis of some substrates, like the bay-region diol epoxides derived from benzpyrene.1381 In the context of enzyme mimics these reactions are primarily of curiosity value DNA lacks the conformational flexibility and the chemical functionality to offer the prospect of efficient catalysis for ordinary reactions. 

DIOLS FROM LITHIUM [5-LITHIOALKOXIDES GENERATED BY THE REDUCTIVE LITHIATION OF EPOXIDES ... 

B. Mudryk and T. Cohen 173 1,3-DIOLS FROM LITHIUM p-LITHIOALKOXIDES GENERATED BY THE REDUCTIVE LITHIATION OF EPOXIDES 2,5-DIMETHYL-2,4-HEXANEDIOL... 

In contrast to the relative chemical stability of mono-epoxides, diol epoxides of fatty acids (10.52), which are formed from di-epoxides by EH, are subject to a different fate. In such metabolites, intramolecular nucleophilic substitution may occur, such that oxirane opening is accompanied by formation of a tetrahydrofuran ring [134], Such reactions of intramolecular nucleophilic substitution are discussed in detail in Sect. 11.9. In the case of diol epoxides of fatty acids, the resulting tetrahydrofuran-diols (10.53) are part of a much larger ensemble of oxygenated metabolites of fatty acids, the potential cytotoxicities of which are being evaluated [135]. 

Kureshy R. I. Khan N. H. Abdi S. H. R. Patel S. T. Jasra R. V. (2002) Simultaneous produetion of chirally enriched epoxides and 1,2 diols from racemic epoxides via hydrolytie kinetic resolution (HKR/, J Mol Catal, 179 73-77. 

Enantiopure epoxides and vicinal diols are important versatile chiral building blocks for pharmaceuticals (Hanson, 1991). Their preparation has much in common and they may also be converted into one another. These chirons may be obtained both by asymmetric synthesis and resolution of racemic mixtures. When planning a synthetic strategy both enzymic and non-enzymic methods have to be taken into account. In recent years there has been considerable advance in non-enzymic methods as mentioned in part 2.1.1. Formation of epoxides and vicinal diols from aromatics is important for the break down of benzene compounds in nature (See part 2.6.5). 

Scheme 3.4 Bioactivation of benzo[o]pyrene to the ultimate carcinogen , 7,8-trans-diol-9,10-epoxide. Modified from [42].

In conclusion, the chiral salen Co(III) complexes immobilized on Si-MCM-41 colud be synthesized by multi-grafting method. The asymmetric synthesis of diols from terminal olefins was applied with success using a hybrid catalyst of Ti-MCM-41/chiral Co(III) salen complexes. The olefins are readily oxidized to racemic epoxides over Ti-MCM-41 in the presence of oxidants such as TBHP, and then these synthesized diols are generated sequentially by epoxide hydrolysis on the salen Co(lll) complexes. This catalytic system may provide a direct approach to the synthesis of enantioselective diols from olefins. 

Reaction with epoxy aiochols-3 Epoxides formed from (E)-allylic alcohols react regioselectively with organoaluminum compounds to provide 1,2-diols with inversion at C j in high yield. 

However, should you wish to make both syn and anti-diols from an alkene when only one isomer (E- or Z-) can be made, such as cyclopentene 25, you need another method. Epoxidation... 

Kishimoto Y, Ogawa I (2004) Amine-catalyzed, one-pot coproduction of dialkyl carbonates and 1, 2-diols from epoxides, alcohols, and carbon dioxide. Ind Eng Chem Res 43(26) 8155-8162... 

Already in the first reports on olefin oxidation with the MTO/H2O2 system [3], it was noted that the formation of diols from the desired epoxides, caused by the Br0nsted acidity of the system, is a major drawback of this system. The solution for this problem was found in the same report by the addition of a nitrogen base. This method has been explored extensively since and has become an important factor in the MTO-catalyzed olefin epoxidation. 

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