Photo- and thermal isomerization of some 1-methoxyallyl cations

The 1-methoxy-, 1-methoxy-3-rnethyl-, and 1-methoxy-2,3-dimethylallyl cations, 2, 5, and 9, were prepared by treatment of the dimethyl acetals of acrolein, crotonaldehyde, and tiglaldehyde, respectively, with FSO 3 H. Each of these ions was capable of existing in various stereoisomeric forms. The thermodynamically preferred conformation of 2, 5, and 9 all had a C1—O, E configuration and 5 and 9 an E configuration about the C2—C3 bonds. …