3- Aryl-4-amino-2- isoxazole synthesis

An intramolecular aza Diels-Alder reaction of as well electronically neutral N-aryl imines useful for the synthesis of novel tetrahydropyridine derivatives has been introduced by our group [268]. The reactive intermediate 3-43 exhibiting the 2-aza-l,3-butadiene subunit was generated in situ from the aldehyde 3-41 and the amino isoxazole 3-42 and led directly to the diastereomerically pure cycloadduct 3-44 (Fig. 3-14). In contrast to the reactions studied by Barlu-enga, the 2-aza-1,3-butadiene acts as electron-deficient component in this case. 

A one-pot synthesis of 3-methyl-5-aryl-4//-pyrrolo[2,3-<7]isoxazoles was performed in high yields by Sharpless epoxidation of 4-amino-3-methyl-5-styrylisoxazoles <06TL4957>. 1,2,4,5-Tetrazines were condensed with isoxazolylcyclobutanones in methanolic KOH to give conformationally restricted 6-isoxazol-5-yl-6,7-dihydro-5//-[l,2]diazocin-4-ones <06JOC2480>. 

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