Bromoformonitrile oxide

Dipolar cycloadditions of nitrile oxides to the various unsaturated alditol derivatives 92 led to pairs of isoxazolidine regio-isomers, e.g. 93 and 94, each as predominantly one stereoisomer (Scheme 16). The isoxazole 95 was the major product from addition of bromoformonitrile oxide to the nitro-alkene. The nitrile moiety of D-mannononitrile pentabenzoate was transformed into either a 3-substituted 5-methyl-1,2,4-oxadiazole moiety (with NH2OH then AC2O) or a 5-substituted 2-methyl-1,3,4-oxadiazole moiety (with NH4N3 then AC2O, Py) cf. Vol.24, p.l35. The synthesis of 2-(alditol-l-yl) substituted 2-aza-3,7-dioxabicy-clo[3.3.0]octanes by intramolecular dipolar cyclization of 2-0-d y -aldehydo-sugar nitrones is covered in Chapter 24. 

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