Synthesis of perhydroxazin-4-ones. Competitive Mukaiyama versus hetero Diels-Alder reaction in the cycloaddition of 2-aza-3-trimethylsilyloxy-1,3-butadiene and aldehydes

The reactions of 2-aza-3-trimethylsilyloxy-1,3-butadiene with carbonyl dienophiles are described. 2-Aza-1,3-butadienes participate as dienes in the [4+2] cycloaddition with aldehydes to afford perhydroxazin-4-ones in good yields. Experimental results, however, show that a Mukaiyama type two-step reaction must be taken into account. The cycloadducts obtained have proved to be useful intermediates in the synthesis of alpha -amino-beta -hydroxy acids. (C) 2001 Elsevier Science Ltd. All rights reserved.