Oxazolidine ring cleavage

The diastereomers cannot be separated due to cleavage of the 1,3-oxazolidine ring during column chromatography. 

A 1 2 mixture of MejSiNEt2 and Mel induces the ring cleavage of oxazolidines to afford the corresponding A-[2-(trimethylsiloxy)ethyl]imine <02JOC5170>. 

An excerpt of a synthesis of the potent antitumour agent FR-900482 [Scheme 3.126] illustrates the use of an N, O-acetal with additional Af-protection in the form of a 2,2,2-trichloroethoxycarbonyl (TVoc) group (see section 8.3.7) in a multifunctional environment.244 245 The A 0-acetal survived the mildly acidic conditions required to deprotect the p-methoxybenzyl group that preceded the formation of the triflate 1263. Later, reductive cleavage of the Troc group and simultaneous hydrolysis of the oxazolidine ring was accomplished in a single... 

The "heavy-atom method" (which uses a heavy-metal salt of the alkaloid) was not,in this case, sufficiently informative concerning stereochemistry because formation of the salt involved cleavage of the oxazolidine ring present in the base. This particular X-ray study is of considerable interest because nmr spectral studies reported earlier (Pelletier and Mody, ibid-, 1977, 284) indicated that in... 

Defunctionalizations. With Pd(II) catalysts, EtjSiH reduces organic halides and aryl and enol triflates to the hydrocarbons. Reductive cleavage of the C-0 bond of a fused oxazolidine ring proceeds with retention of configuration. ... 

Most of the reactions involving nucleophilic attack at a carbon atom of the ring result in cleavage of the five-membered ring system (which is in most cases either an oxazolidine or an oxazolidinone). Basic hydrolysis of... 

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. 

A rare example (136) of the 1,2,4-oxathiazolidine ring system rearranges to the oxazolidine (137) with a half life of 14 h in CDC13 at 52 °C, cleavage of the S—O bond leading either to an intermediate diradical or to a dipolar ion (78AG(E)455). 

Cleavage of oxazolidines. A route to a-substituted allyl amines starts from A-acetyl (X-amino acids via the oxazolidinones. The latter compounds are converted to dichloromethylene derivatives by reaction with PhjP-CCl and the final step involves dechlorination and ring opening (and removal of an HCO unit) with Na in refluxing THF. 

Chemical or catalytic reduction of oxazoles results in cleavage of the heterocyclic ring involving fission of the bond between C-2 or C-5 and oxygen simple reduction products such as oxazolines or oxazolidines have never been isolated. Dornow and Eichholtz371 have made some valuable... 

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