The Use of Nitrone Cycloadditions in the Synthesis of Beta-Amino Aldehydes and Unsaturated Amines.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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Some general parameters have been established for nitrone cycloadditions to 2-substituted vinylsilanes. Nitrones and vinylsilanes react to give isoxazolidines with the TMS group at either the C-5 or C-4 position. While 5-TMS isoxazolidines have been fragmented to Alpha,beta-unsaturated aldehydes, these isoxazolidines may also be converted into beta-amido aldehydes. Beta-Amido aldehydes were then elaborated into Beta-amino acids and beta-lactams. However, 4-TMS isoxazolidines, which are the predominant regioisomers from the cycloaddition, have been converted to allylic amines via a Peterson elimination methodology with stereospecific control of the double bond geometry. These allylic amines were subsequently converted stereoselectively into gamma-lactams via a CuI mediated cyclization. Nitrone and allyltrimethylsilane produced 5-trimethylsilylmethyl isoxazolidines exclusively. Using Peterson elimination methodology, these isoxazolidines were subsequently converted into homo allylic amines.
- Organic Chemistry