Intramolecular nitrone-allene cycloadditions - Journal of the American

Cycloaddition Involving One Alkyne and Two Nitrone Groups. Hans Günter Aurich , Frank Biesemeier , Klaus Harms. Liebigs Annalen 1997 1997 (3), 46...
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drogen atoms attain almost complete equivalence in the molecular ion of toluene, and that a single 13Catom in position a 2or 13 , 4 - ~ r2, as shown in the present workis lost statistically in the path leading to C6H6+ions. Carbon-I3 label retentions in the C6H5+ion (eq 1) derived from toluene-a,l-l3C2(1)314further indicated that - H.

C?Hs.+

- CzHz

+C?H7+ + m* = 46.4

I

VI

.J l2%+

CjHs+

(1)

the tropylium ion formed is best represented as one in which the carbon atoms have all lost positional identity related to their toluene origin, Le., a randomized tropylium ion (11). The latter may arise (a) by a series of

VI1

@+

VI

+

VI1

C6H6+ions should be formed if path b alone is operative. However, label retentions shown in Table I reveal the Table I. High-Resolution Mass Spectral Peaks ~~

I

I1

I11

rv

(3) I