Organic synthesis oxirane

Also known as glycol dinitrate. eth-o,len m,trat ethylene oxide orgchem 1. (CH2)20 A colorless gas, soluble in organic solvents and miscible in water, boiling point 11°C used in organic synthesis, for sterilizing, and for fumigating. 2. Also known as 1,2-epoxyethane epoxide oxirane eth-3,len ak,sTd ... 

The reaction occurs quickly at low temperature, with inversion of configuration at the attacked carbon center. The oxirane is reacting usually at the less hindered site. This reaction has found widespread use in organic synthesis , particularly in the case of stabilized organolithium and alkynyllithium species (see Section IV.B.2). In the intramolecular versions, the presence of BF3 has been reported to modify the regioselectivity". Other Lewis acids such as organolanthanids or LiC104 have also been used to a lesser extent. 

Early-on it was discovered that these Salen compounds, and the related six-coordinate cations [6], were useful as catalysts for the polymerization of oxiranes. These applications were anticipated in the efforts of Spassky [7] and in the substantial work of Inoue [8]. Subsequently, applications of these compounds in organic synthesis have been developed [9]. Additional applications include their use in catalytic lactide polymerization [10], lactone oligomerization [11], the phospho-aldol reaction [12], and as an initiator in methyl methacrylate polymerization [13]. 

Chiral alkenyl and cycloalkenyl oxiranes are valuable intermediates in organic synthesis [38]. Their asymmetric synthesis has been accomplished by several methods, including the epoxidation of allyl alcohols in combination with an oxidation and olefination [39a], the epoxidation of dienes [39b,c], the chloroallylation of aldehydes in combination with a 1,2-elimination [39f-h], and the reaction of S-ylides with aldehydes [39i]. Although these methods are efficient for the synthesis of alkenyl oxiranes, they are not well suited for cycloalkenyl oxiranes of the 56 type (Scheme 1.3.21). Therefore we had developed an interest in the asymmetric synthesis of the cycloalkenyl oxiranes 56 from the sulfonimidoyl-substituted homoallyl alcohols 7. It was speculated that the allylic sulfoximine group of 7 could be stereoselectively replaced by a Cl atom with formation of corresponding chlorohydrins 55 which upon base treatment should give the cycloalkenyl oxiranes 56. The feasibility of a Cl substitution of the sulfoximine group had been shown previously in the case of S-alkyl sulfoximines [40]. 

This route can be used to generate vinyl oxiranes, useful intermediates for organic synthesis <2000TL7309, 2002JOC9083, 2003JOC2060>. Aryl epoxides have been made and have been used as intermediates in the context of total synthesis venture <2004T9725>. 

Deoxygenation of oxiranes to olefins is an important method in organic synthesis and in proving structures. A varied series of reagents have been used for this purpose in the past decade. 

Alcohols can be obtained from many other classes of compounds such as alkyl halides, amines, al-kenes, epoxides and carbonyl compounds. The addition of nucleophiles to carbonyl compounds is a versatile and convenient methc for the the preparation of alcohols. Regioselective oxirane ring opening of epoxides by nucleophiles is another important route for the synthesis of alcohols. However, stereospe-cific oxirane ring formation is prerequisite to the use of epoxides in organic synthesis. The chemistry of epoxides has been extensively studied in this decade and the development of the diastereoselective oxidations of alkenic alcohols makes epoxy alcohols with definite configurations readily available. Recently developed asymmetric epoxidation of prochiral allylic alcohols allows the enantioselective synthesis of 2,3-epoxy alcohols. 

Most of the examples of seleniranes and telluriranes shown as the unstable intermediates in the organic synthesis are derived from oxiranes. As discussed previously in Section 1.07.6.2, seleno-cyanate anions react with epoxides at room temperature to deposit selenium via the selenirane intermediate and form the corresponding alkenes. On the other hand, triphenylphosphine selenide and trifluoroacetic acid constitute an effective and mild combination of reagents for carrying out the deoxygenation of epoxides (67) to alkenes via cyclic intermediate (68) (Scheme 12) <73CC253>. 

Hudlicky, T. Reed, J.W. in Comprehensive Organic Synthesis, Trost, B.M. Fleming, I., Eds. Pergamon Oxford, 1991 Vol. 5, p899. (Review of vinylcyclopropane to cyclopentene rearrangement and its heterocyclic variants, i.e. cyclo-propylimines and ketones, vinylaziridines and oxiranes, etc.). 

Reactions of oxiranes, application to organic synthesis 84S629. 

Until about 30 years ago, hydrazones derived from carbonyl compounds were not used in organic synthesis. They were used only for analytical purposes , and as protecting groups of aldehydes and ketones ". Corey investigated dimethylhydrazones of ketones and aldehydes with a-hydrogens, and found that they undergo deprotonation with LDA or BuLi in THF at the a-carbons to the hydrazonic moiety in 90-100% yield. The formed lithium compounds, used as enolate anion equivalents, create new carbon-carbon bonds in their reaction with different electrophiles such as alkyl halides or oxiranes, ketones and aldehydes (equation 21). 

Organotrifluoroborates in organic synthesis (reactions with oxiranes, epox-idation of, hetaryltrifluoroborates in Suzuki reaction) 05AA49. 

Catalytic activity and organic synthesis Bimetallic-p-oxoalkoxides are used as highly active catalysts for the polymerization of oxiranes, thiiranes, and lactones. Their reactivity can... 

The oxirane oxidation of sulfides has found applications in organic synthesis [13, 14]. For example, sulfoxidation of disulfide 1 with dioxirane afforded disulfoxide 2 in 98% yield (Eq. (8.2)) [13]. 

Epoxides are versatile organic intermediates due to the reactive oxirane moiety, which can be opened by various nucleophiles or undergo elimination, reduction, or rearrangements to a multitude of more elaborate intermediates with the retention or inversion of chirality [1, 2], Enantiopure epoxides, in particular, play an important role in organic synthesis and the pharmaceutical industry [3,4], In recent decades, there have been enormous advances in the development of catalysts, including chemical catalysts and biocatalysts, for the production of chiral epoxides [5-10],... 

N-tosylimino-oxysulphurane. This ylide reacts in high yield with carbonyl compounds to afford oxirans in a reaction analogous to that effected by sulphonium or oxysulphonium ylides. Optically active phenylmethylsul-phoximine could be tosylated and converted into an ylide with sodium hydride in DMSO, and it reacted with acetophenone to afford optically active 1-phenyl-1-methyloxiran. The ylide (156 R = R = Me) also effected additions to conjugated carbonyl compounds, such as co-benzoylstyrene, to afford l-phenyl-2-benzoylcyclopropane. Johnson recently has reviewed the use of N-tosyliminosulphoxonium ylides in organic synthesis. 

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