Explosion of 4-Acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium Perchlorate and Replacement by Tetrafluoroborate

In December, 1998, I published a paper (J. Org. Chem. 1998 63 , 9367) describing the synthesis and reactions of two oxoammonium salts, 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium perchlorate (1) and tetrafluoroborate (2). These salts are non-heavy metal, colorimetric oxidizing agents for the conversion of alcohols to aldehydes or ketones in essentially quantitative yields with minimal work-up procedures [1,2].

Almost all of the experimental procedures described were related to the perchlorate 1, although the oxidants 1 and 2 seemed to have nearly identical properties. The air-dried perchlorate has been used for about six years and was thought to be quite stable. However, when an 8 g. sample was dried over P₂O₅ under high vacuum at 55°C., it detonated. Damage was minimal, but the explosion was quite violent.

Those who might have prepared a supply of the perchlorate are urged to destroy it by dissolving it in water and reducing it with ethanol and NaHCO₃ as described in the paper.

The tetrafluoroborate 2 is quite stable up to at least 95°C. under the conditions described above and has the same outstanding oxidizing properties as the perchlorate.

Acknowledgment: Partial financial support was provided by the National Science Foundation (Grant CTS-9632391).