Stereochemistry of the Deamination of Spiropentylamine

The stereochemistry of the deamination of (−)-spiropentylamine in acetic acid has been studied, and it was found that one of the major products, (−)-spiropentyl acetate, was formed with essentially complete inversion of configuration. This suggests that it is formed via an S N 2 displacement on the spiropentyldiazonium ion. The stereochemistry was established by the conversion of (−)-spiropentanecarboxylic acid to (−)-spiropentylamine via a Curtius rearrangement that proceeds with retention of configuration. The (−) acid also was converted to spiropentyl methyl ketone with methyllithium and then to (+)-spiropentyl acetate via the Baeyer−Villiger reaction that also results in retention of configuration. The deamination of N -nitroso- N -spiropentyl urea was studied in methanol, and spiropentyl methyl ether was a major product. Similarly, the reaction in water led to spiropentanol. The latter reactions also lead to 2-methoxymethyl- or 2-hydroxymethyl-1,3-butadiene, respectively, corresponding to the alternative mode of reaction via a cyclopropyl cation−allyl cation rearrangement.