Oxygen-containing oxiranes

Epoxide adhesives are based on precursors containing the three-membered, oxygen-containing oxirane group ... 

This section covers the synthesis of aziridines, oxiranes, /J-lactams and oxetanes. Aziridines are fairly important moieties in bioactive molecules and thus new routes for their synthesis are constantly being developed. /1-Lactams are probably the most important heterocyclic compounds that contain a single nitrogen atom, due to their importance in penicillin and cephalosporin chemistry. Their synthesis and chemistry has received much attention and much of this work has been reviewed544. The oxygen-containing heterocycles are much less commonly synthesized from double-bonded functional groups. 

The transformation of oxiranes into other oxygen-containing heterocyclic systems (e.g., cyclic ethers, dioxolanes, orthoesters, lactones, and cyclic carbonates), via a variety of heterolytic, homolytic, enzymatic, and single-electron transfer processes, has been reviewed <2004RJ01227>. 

Oxygen-containing heterocyclic homologues of ethers exhibit two absorption bands, with the exception of oxirane which has only one absorption maximum at... 

Starting from oxiranes, oxygen-containing macrocycles can also be prepared a good example of this is the formation of the ten-membered oxygen-containing heterocycle 126 via the condensation of chloral hydrate and oxirane using the phase-transfer technique. 

LG (leaving group), e.g. Cl, Br, OSOjAr, OMs, OBz, oxygen contained in an oxirane or oxetane ring Scheme 1... 

Preparation. - Oxidation of Alkenes to Oxirans, using Oxygen or Oxygen-containing Gases. Research into the improvement of the silver catalysts that are used in the commercial oxidation of ethene has resulted in continued interest in the doping of the catalyst with alkali-metal salts, particularly... 

Preparation.—Catalytic Oxidation of Alkenes to Oxirans, using Oxygen or Oxygen-containing Gases. The mechanism for the conversion of the phenol (1) into the epoxy-quinol (4) by molecular oxygen in Bu OK-Bu OH has been investigated (Scheme 1)." The first step is the formation of hydroperoxide (2), which is converted into hydroperoxide (3) via a -n--complex intermediate the yield of (4) increases with temperature. 

Five-membered Oxygen-containing Rings. The reaction of aldehydes with 1,1-dicyano-oxirans (77) gives 1,3-dioxolans (79). The authors suggest, by... 

As anticipated by the formation of oxiranes (oxacyclopropanes, epoxides) from halohydrins, the four-membered oxygen-containing ring, oxetane (oxacyclobutane), can be prepared by heating 3-chloropropanol (HOCH2CH2CH2CI) with potassium hydroxide (KOH) (Equation 8.51). 

The oxygen containing three-membered ring systems known either as oxiranes or epoxides are special ethers in the sense that they are both readily formed and highly reactive. These substances are commonly formed by one of three methods intramolecular nucleophilic displacement, methylenation of a carbonyl compound or epoxidation of an olefin. All three synthetic approaches are represented in the phase transfer literature. 

The parent saturated three-membered ring systems containing nitrogen, or oxygen, or sulphur as the heteroatom are known as aziridine (1), oxirane (2) and thiirane (3). 

The term epoxy, epoxy resin, or epoxide (Europe) refers to a broad group of reactive compounds that are characterized by the presence of an oxirane or epoxy ring, shown in Fig. 2.1. This is represented by a three-member ring containing an oxygen atom that is bonded with two carbon atoms already united in some other way. 

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