Oxirane-ring opening, intramolecular

Intramolecular oxirane-ring opening at C-4 substituted anhydride 148, where Nu = -0 (CH2CH2) OH or -O (CH2)raNH2, affords a new heterocyclic ring fused to 1,6-anhydro-jS-D-hexopyranose.443... 

An intramolecular oxirane ring-opening reaction can likewise be seen in Eq. 295. ... 

A transition metal catalyzed synthesis of ethers by carbene insertion into the O—bond has been reported. Not only saturated but also unsaturated alcohols can be utilized in this catalytic process. ° Intermolecular and intramolecular oxirane ring opening reactions by alkoxides and phenoxides also provide efficient and stereospecific preparations of acyclic and cyclic ethers. The procedures have been surveyed in detail. ... 

Regioselective C-2 amination of 2,3-epoxy alcohols can be realized by intramolecular oxirane ring opening of the carbamates prepared by the reaction of the epoxy alcohols with isocyanates." -" In some cases, however, acyl transfer is a serious side reaction (Scheme 59)." ... 

Intermolecular and intramolecular oxirane ring opening reactions by alkoxides and phenoxides also provide efficient and stereospecific preparations of acyclic and cyclic ethers. The procedures have been surveyed in detail. ... 

Two minor products formed during the oxidation of colupolone (193) with molecular oxygen have been shown to have structures (195) and (196). The main product of oxidation is cohulopone (194), and (195) and (196) are considered to be derived from (194) by epoxidation and subsequent opening of the oxiran ring and intramolecular acetalization. ... 

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. 

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. 

Guanidines are useful nucleophiles in the intramolecular ring opening of epoxides <2003TL3075>. The intramolecular addition of an amide anion to an oxirane in a 6-o o-fashion formed 2-ketopiperazine derivatives <20040L4069>. This reaction type was also used in a recent quinine synthesis <2004TL3783>. 

Carbanions. These add to the C-3 position of (5)-(l), affording epoxides (3) after intramolecular displacement of the tosylate group and in situ ring closure of the ring-opened intermediate (eq 4). Deprotonation of oxirane (3) leads to rearrangement to cyclopropane derivatives. ... 

---