Reactions of nitroarenes with secondary and tertiary carbanions bearing both a leaving group and electron-withdrawing group: An approach to dihydronaphth [2,1-c]isoxazole N-oxides and dihydroisoxazolo[4,3-f]quinoline N-oxides

摘要

2-Nitronaphthalene (1) and 6-nitroquinoline (2) underwent direct cyclocondensation with secondary and tertiary carbanions derived from a methylene and methine group bearing both a leaving group and electron-withdrawing group (e.g., methyl chloroacetate, ethyl chloroacetate, chloroacetonitrile, methyl 2-chloropropionate, ethyl 2-chloropropionate and 2-chloropropionitrile) in the sodium hydride/NN-dimethylformamide system at low temperature, giving the corresponding dihydronaphth[2,1-c]isoxazole N-oxides 3 and dihydroisoxazolo[4,3-f]quinoline N-oxides 4. On the other hand, nitroarenes 1 and 2 reacted with secondary carbanions in the sodium hydride/tetrahydrofuran system to yield the corresponding conventional vicarious nucleophilic substitution (VNS) products 5 and 6. [References: 34]