Unique Formation of an Isoxazoline-N-Oxide from Nitrodibromoacetonitrile and Tetramethylethylene

摘要

Tetramethylethylene and nitrodibromoacetonitrile in dichloromethane at 25C gave 3-cyano-4,4,5,5-tetramethyl1-2-isoxazolin-2-oxide (45%) and 2,3-dimethylbutane (42%). In the first example of the formation of an isoxazoline-N-oxide by a reaction between an olefin and a nitrohalomethane, tetramethylethylene 1(2 moles) and nitrodibromoacetonitrile1 (NDBA) 2 in dichloromethane at 25C gave 3-cyano-4,4,5,5-tetramethyl-2-isoxazolin-2-oxide 3 (45%) and 2,3-dibromo-2,3-dimethylbutane 4 (42%), a known compound, eq(1). The structure of the new heterocycle 3 was confirmed by an X-ray crystallographic analysis. It is proposed that the reaction proceeded from an intermediate bromonium methane 5/6. Similiar abstraction of a positive nitro or halo substituent is amply documented for reactions between olefins and tetranitromethane, trinitroacetonitrile, bromotrinitromethane, and iodotrinitromethane. The formation of the heterocycle 3 and the dibromide 4 was attributed to straightforward interaction between the intermediate 5/6 and the olefin 1, eq(2), without differentiation between concerted and stepwise pathways. (Metal salts of negatively substituted derivatives of nitromethane converted olefins in aprotic solvents at 20-50C to isoxazoline-N-oxides). (AW)