A novel approach to bis-isoxazolines using a latent form of cyclopentadienone

We describe the synthesis of a range of both racemic and homochiral 4-alkyl - and 4-aryl-8-hydroxy-2-oxa-3-azabicyclo[3.3.0]oct-3-en-6-ones (isoxazolin es) from the 1,3-dipolar cycloaddition reactions between alky- and aryl-nit rile oxides and 4-alkoxycyclopent-2-enones. Elimination of the 8-hydroxy gr oup and subsequent additional cycloaddition reactions provided 5,9-disubsti tuted-3,11-dioxa-4,10-diazatricyclo[6.3.0(1,8).0(2,6)]undeca-4,9-dien-7-one s (bis-isoxazolines) formally derived from cyclopentadienone.