A novel salicylaldehyde based mineral supported expedient synthesis of benzoxazinone nucleosides

An expedient mineral (montmorillonite K-10 clay) catalysed cycloisomerisation of salicylaldehyde 4-(β-d-ribo- or β-d-2′-deoxyribofuranosyl)semicarbazones yields benzoxazinone nucleosides, 4-hydrazino-3,4-dihydro-3-(β-d-ribo- or β-d-2′-deoxyribofuranosyl)-2H-benz[e]-1,3-oxazin-2-ones, which readily undergo reductive dehydrazination on alumina-supported copper(II) sulfate to furnish 3,4-dihydro-3-(β-d-ribo- or β-d-2′-deoxyribofuranosyl)-2H-benz [e]-1,3-oxazin-2-ones under solvent-free microwave irradiation.