Ring opening of oxirans

Epoxide-hydrolases as asymmetric catalysts for ring opening of oxiranes 97T15617. 

Key steps, as shown in Scheme 4-15, involve the formation of a urethane intermediate 37 by treating epoxide 36 with methyl isocyanate in the presence of sodium hydride. Intramolecular A-nucleophilic ring opening of oxirane affords oxazolidine 38. Subsequent treatment furnishes product 34. 

Cyclic carbonates have been prepared in the regiospecific ring-opening of oxiranes by butyrolactones catalysed by the quaternary ammonium salt (Scheme 3.6)... 

Selected examples of ring-opening of oxiranes by chloroalkanes to yield allyl ethers... 

Selected examples of the ring-opening of oxiranes with perfluorocarboxylic esters... 

Ring opening of oxiranes using azide is followed by Staudinger reduction of the intermediate azido alcohol to give aziridines. 

Yamashita, H. (1988) Metal(ll) J-tartrates catalyzed asymmetric ring opening of oxiranes with various nucleophiles.. Bull. Chem. Soc. Jpn., 61 1213-1220. 

The terms epoxy resin (EP) and ethoxyline resin are used to describe polyphenol derivatives and other compounds which resinify by ring opening of oxirane rings. The polyphenols are typically diphenylolmethane or bis henol A [2,2-bis(4-hydroxyphenyl)propane] the latter diol is obtained by the condensation of phenol and acetone. Bisphenol A, is the most widely used phenol for epoxy resin production. 

Few solid-phase syntheses of oxazoles have been reported (Table 15.17). The most general strategy is the dehydration of a-(acylamino) ketones (Entry 2, Table 15.17) or 2-(acylamino)phenols (Entry 1, Table 15.17). Oxazolidin-2-ones have been prepared by intramolecular nucleophilic cleavage of carbamates from insoluble supports (Entries 5 and 6, Table 15.17). Resin-bound 2-aminoethanols, which are accessible by nucleophilic ring-opening of oxiranes with amines, undergo cyclocondensation with aldehydes to yield oxazolidines [220,221]. These compounds are unstable towards acids, and can be released from the support only under neutral or basic reaction conditions. 

The ring-opening of oxiranes, leading to the formation of isomeric carbonyl compounds by the action of acid catalysts as a result of rearrangement, is of continuing interest (refs. 1-4). However, most of these studies focus mainly on the transformations of terpene oxides or oxiranes with other functional groups in the liquid phase, under homogeneous reaction conditions. 

Olah et al.724 have shown that Nafion-H induces the ring opening of oxiranes under mild conditions to afford various products. Substituted oxiranes undergo hydrolysis or alcoholysis to yield 1,2-diols or 1,2-diol monoethers, when treated with Nafion-H under mild conditions in the presence of water or alcohols, respectively. Cycloalkene oxides give the corresponding trans products stereoselectively [Eq. (5.273)]. 

Nucleophilic ring opening of oxiranes gives intermediates of the type 22, which readily ring-closed (Scheme 8) <2004JOC8780>. A similar reaction can be carried out in one step <2003GC436>. 

Das, U. Crousse, B. Kesavan, V. Bonnet-Del-pon, D. Begue, J.-P. Facile ring opening of oxiranes with aromatic amines in fluoro alcohols. /. Org. Chem. 2000, 65, 6749-6751. 

Lu, S. (2007) Photochemically catalyzed ring opening of oxirane carbonitriles and [3 + 2] cycloaddition with olefins ... 

Scheme 6 Ring opening of oxiranes and aziridines to 1,3-dipolar valence tautomers.

Ring-opening of oxiranes, oxetanes and other cyclic ethers... 

The asymmetric ring opening of oxiranes (and aziridines) with carbon nucleophiles has been reviewed by Pineschi <2006EJO4979>. 

From epoxides. A very efficient access to tetrahydrofuran derivatives has been developed based on ring opening of oxiranes with selenolates. For instance, preparation of 2,4-disubstituted tetrahydrofurans from epoxides is shown in Eq. (3) [ 11 ]. Opening of the epoxide 19 with diphenyldiselenide/NaBH4 followed by prenylation gives the radical precursor 20 in excellent yield. Cyclization furnishes the tetrahydrofuran 21 in almost quantitative yield but with a modest stereocontrol. The oxirane opening approach described here competes with the electrophilic alkoxyselenenylation reported below (Sect. 2.1.2). 

Nucleophilic ring-opening of oxiranes by lithium dialkylcuprates occurs at the sterically less-hindered side and the corresponding alcohol is formed.The reaction can be carried out under mOd conditions and the side-reactions observed with other organometallic compounds can be avoided. The mechanism of the transformations has been treated in detail. With MejCuLi the reaction proceeds stereoselectively and the new C-C bond is formed on the side opposite the C-0 bond of the oxirane (Eq. 

The ring-opening of oxiranes with ammonia and amines is one of the general methods for the preparation of 1,2-aminoalcohols. This procedure has acquired great importance in practice too. The process is illustrated in a new example in Eq. 317. ... 

Lewis acid promoted ring opening of oxiranes with cvgano-silanes or -stannanes is reported. TMS-CN cleaves the C—O bond in the presence of AlCb, Et2AlCl, Ti(OPr )4 or LnX3, and 3-hydroxy-... 

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