Oxazolidinones ring opening

Polyfunctionalized pyrrolidines were diastereoselectively synthesized via ring-closing metathesis of 3-allyl-4-vinyl-2-oxazolidinones. Compound 202 gave the bicyclic system 203, converted into 204 through cis-dihydroxylation and oxazolidinone ring-opening <04SL49>. 

Marti, R.E., Yan, B. and Jarosinski, M.A., Solid-phase synthesis via 5-oxazolidinones. Ring opening reactions with amines and reaction monitoring by single-bead FTIR microspectroscopy, J. Org. Chem., 62 (1997) 5615-5618. 

For the isoxazolines 284 substituted at position 3, ring-chain tautomerism is depicted by the equilibrium 284 and 285-287 (Scheme 103). In general the cyclic tautomers 284 are strongly preferred. The ring-opened forms exist in equilibrium with 284 in rare cases [95ZOB705 96AHC(66)1, p. 21]. The equilibrium of the oxazolidinones 288 [78MI1, p. 107] is affected by the nature of the solvent. 

Inclusion of the amide in oxazolidinone functionality can be used to overcome diene statial disposition issues, for example in the conversion of 19 into 20 yields of 20 were generally high (Table 2). Ring opening of the oxazolidine moiety with or without loss of the mandelic acid moiety then afforded the corresponding azepin-2-ones <06TL3625>. 

Finally, single bead FT-IR has been further exploited in many applications, such as the study of the tetrapropylammonium perrutherate (TPAP)-catalyzed oxidation of supported alcohols [167], the ring opening of a supported oxazolidinone [173], and the solid-phase synthesis of a benzimidazole [174]. 

Alkoxy-2(3/f)-oxazolones 47 react with aliphatic and aromatic aldehydes in the presence of Lewis acid catalysts to produce alkyl 2-oxazolidinone-4-carbox-ylates 291 ° by successive ring opening and reclosure. 

This method 1011 includes the isolation of the oxazolidinones 9 before reductive ring opening. A one-pot method without isolation of the oxazolidin-5-ones has also been developed11061 and mainly used to prepare a variety of 7V-Fmoc-7V-methyl co-carboxylic adds. 

Interestingly, the catalytic reaction yielded predominantly the threo-4-(chloro-methyl)oxazolidinones, whereas under thermal conditions in 1,1,2,2-tetrachlo-roethane (TCE) the eryth.ro isomer was formed exclusively. If the reaction proceeded via aziridine formation followed by nucleophilic ring opening, the product stereochemistry would be erythro. As this was not the case, the involvement of an N-centered radical species was suggested (Figure 3.8). 

The stereochemistry of the cyclohexene adduct was established as cis by comparison of the product with the authentic tnms-isomcr prepared by ring opening of cyclohexene oxide with tert-butylamine. Similarly, the products obtained from (Z)- and ( )-l-deuterio-l-decene were converted to diastereomeric oxazolidinones which were compared with the authentic diastereo-mers. Furthermore, different diastereomers were obtained from ( )- and (Z)-l-phenylpropene, It is therefore reasonable to assume complete syn addition for all alkenes. 

Substituted oxazolidin-5-one derivatives, which are prepared from N -protected a-annino dicarboxyhc acids and paraformaldehyde, are employed for dual protection of the a-annino and a-carboxy groups in the synthesis of P-aspartyl and y-glutamyl esters (Scheme 4).Py For this purpose the oxazolidinone derivatives are synthesized by treatment of the Z amino acids with paraformaldehyde in a nnixture of acetic anhydride, acetic acid, and traces of thionyl chloride or by azeotropic distillation of the Z amino acids with paraformaldehyde and 4-toluenesulfonic acid in benzene. The resulting heterocychc compounds are readily converted into the tert-butyl esters with isobutene under acid catalysis. Esterification is achieved with tert-butyl bromidet or with Boc-F.P l Finally, the oxazolidinone ring is opened by alkaline hydrolysis or catalytic hydrogenolysis to yield the tert-butyl esters. 

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