Synthesis of Alkenediazonium Salts

Attempts to trap the diazonium intermediate 2.252 by addition of nitrosyl chloride to a solution of the amine 2.251 in CH2CI2 at — 70°C, followed by addition of a methanol solution of the sodium salt of 2-naphthol, gave no azo compound. (It seems to the present author that the reaction conditions for these trapping experiments have not been studied in sufficient detail to be conclusive.) In their second paper, Curtin et al. (1965 b) selected 3-amino-2-phenyl-l//-inden-l-one (2.256) for 

2 Methods for the Preparation of Alkane, Alkene, and Alkyne Diazo Compounds 

Further and important support for the hypothesis of alkenediazonium ions in the decomposition of nitroso oxazolidinones is provided by investigations by Kirmse et al. (1979) with the N-labeled nitroso compounds 5,5-dimethyl-3-nitroso-[3- N]-l,3-oxazolidin-2-one (2.259, R = H R = R = CH3) and 5,5-pentamethyl-ene-3-nitroso-[3-i N]-l,3-oxazolidin-2-one (2.259, R = H, R -R = -[CH2]5-). The authors determined the N content of products of decompositions conducted in the presence of lithium azide. The results are consistent with A-coupling of the intermediate with azide ions (for coupling of arenediazonium ions with azide ions see Zollinger, 1994, Sect. 6.4). 

If a H-atom is also present in position 5 in the nitroso oxazolidinone 2.259 (R = H) dediazoniation gives only disubstituted alkynes (2.266). 

By intention, we have reviewed that work here only superficially. We agree with the short statement by Stang (1978) that the mechanism of these ring opening reactions is still not completely understood. 

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