Oxazolidinones Staudinger reaction

Staudinger Reactions. Chiral oxazolidinones have been employed as the chiral control element in the Staudinger reaction as well as the ultimate source of the a-amino group in the formation of p-lactams." Cycloaddition of ketene derived from 4-(S)-phenyloxazolidylacetyl chloride with conjugated imines affords the corresponding p-lactams in 80-90% yields with excellent diastereoselectivity (eq 54). The auxiliary can then be reduced under Birch conditions to reveal the a-amino group. 

Saul, R, Kopf, J, Koell, P, Synthesis of a new chiral oxazolidinone auxiliary based on D-xylose and its application to the Staudinger reaction. Tetrahedron Asymmetry, 11, 423-433, 2000. 

Oxazolidinone aiudharies based on o-xylose [66] and D-mannitol [67] residues were converted into corresponding carboxylic acids 79 and 80 which after activation were used for stereoselective Staudinger reaction with diaryl, or aryl-styryl imines. hi the first case, an excellent diastereoselectivity was obtained to afford 81 with high preponderance [66]. hi the second case. 

Chiral ketene fragments have proven to offer more general utility in the quest for enantioselective Staudinger reactions. In particular, ketenes containing the Evans oxazolidinone have proven to offer high diastereoselectivities in the synthesis of 3-amino-P-lactams. The ease of preparation of the carboxylic acid precursor, the low cost of the auxiliary, and the facile unmasking of the 3-amino group from the auxiliary all... 

Two new glucose-derived oxazolidinones have been prepared, and converted to iV-acyl derivatives of type 204 (R = Me or Piv). The dialkylboron enolates derived from 204 underwent aldol reactions to give syn-products 205, with diastereomeric ratios between 8 1 and 16 1. The same group has also made the oxazolidinone 206 from D-xylose. When this was treated with Mukaiyama s reagent (2-chloro-l-methylpyridinium iodide) in the presence of an imine, a Staudinger ketene-imine cyclization occurred to give a p-lactam such as 207, the structure of which was confirmed by X-ray crystallography, in >98% de. ... 

Recently, Delpiccolo and Mata have also explored the asymmetric synthesis of monocyclic 3,4-substituted (3-lactams (Scheme 3.15). They employed the same Staudinger-type cycloaddition reaction with the chiral glycine derivative, 4(5)-phenyloxazolidylacetyl chloride (72). The oxazolidinone moiety functioned effectively as a chiral auxiliary, and a small library of optically active p-lactams 75 were obtained following cleavage with 10% TFA/DCM and subsequent conversion to the methyl esters (diastereoselec-tivity ranged from 8/1 to >25/1). 

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