EI Mass Spectra of the New Ring-enlargement Products in the Lead Tetraacetate Oxidation of l-2(10)-Pinene

Abstract

From the EI mass spectra of the two new ring-enlargement products, (1R,6S)-7,7-dimethylbicyclo[4.1.1]octan-2-one and (1S,6S)-7,7-dimethylbicyclo[4.1.1]octan-3-one obtained by the lead tetraacetate oxidation of l-2(10)-pinene, we can find the distinct fragment ions at m/z 110 and m/z 111, respectively. The difference between the structures of these two ions was discussed by using B/E constant linked scan method and their exact mass spectral data. Consequently, it was considered that the ion of m/z 110 keeps the gem-dimethyl bridged structure, while the ion of m/z 111 is formed by the elimination of gem-dimethyl group.