Synthesis of 4-carbethoxy-4H-3-substituted-isoxazol-5-ones and their conversion into novel spiroheterocycles

Interaction of diethyl alpha-acyl/aroylmalonates 1 with hydroxylamine hydro chloride 2 afford 4-carbethoxy-4H-3-substituted-isoxazol-5-ones 3 and 3-sub stituted-4H-5-oxo-isoxazol-4-carboxylic acids 4. Bromination of 3 affords 4 -bromo derivatives 5, which with thiocarbamides, 4-substituted thiosemicarb azides give 2-alkyl/arylimino-4, 9-dioxo-3, 7-diaza-8-oxa-6-substituted-1-t hia-(3H)-spiro[4.4]nonan-6-enes 7 and 2-alkyl/arylimino-5, 10-dioxo-9-oxa-7 -substituted-1-thia-3, 4, 8-triaza-(3H, 4H)-spiro[5,4]dec-7-ene 8. Characte risation of the products has been done on the basis of spectral (IR, H-1 NM R and C-13 NMR) data.