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Reactions of chromones with methyl ketoximes in the presence of lithium diisopropylamide follow the nucleophilic 1,2 addition mechanism to give spiro[4H chromene 4,5´ isoxazolines] in good yields. The isoxazoline ring in spiro[4H chromene 4,5´ isoxazolines] undergoes open ing under the action of conc. H 2 SO 4 , yielding α,β unsaturated oximes. Their nitrosation and bromination lead to the corresponding spiroisoxazolines, while the Beckmann rearrangement, to α,β unsaturated amides. The latter are also formed directly from spiro[4H chromene 4,5´ isoxazolines] under the action of PCl 5 . N Substituted acetophenone hydrazones in the pres ence of lithium diisopropylamide react at the C(4) atom of 2 trifluoromethylchromone, while acetophenone anil under the same conditions, at the C(2) atom.

2006 Benzopyran derivatives R 0350 Spiro[4H-chromene-4,5'-isoxazolines] and Related Compounds: Synthesis and Reactivities. -The reaction of chromones (I) with methyl ketoximes (II) affords spiro compounds (IV), which are used for the preparation of derivatives (IX) and (X). Reactions of chromone (Ia) with hydrazones and acetophenone anil are also studied [cf. compounds (XII), (XIV), and (XVI)]. -(SOSNOVSKIKH*, V. Y.; SIZOV, A. Y.; USACHEV, B. I.; KODESS, M. I.; ANUFRIEV, V. A.; Russ. Chem. Bull. 55 (2006) 3, 535-542; Gorky Ural State Univ., Ekaterinburg 620083, Russia; Eng.) -R. Staver 52-144