Säurekatalysierte Dienon‐Phenol‐Umlagerungen von 6‐Propargyl‐6‐methyl‐cyclohexa‐2,4‐dien‐1‐onen; ladungskontrollierte, aromatische [1 s , 2 s ]‐ und [3 s , 4 s ]‐sigmatropische Reaktionen

The acid catalysed dienone‐phenol rearrangement of methyl substituted o ‐propargyl‐cyclohexadienones (scheme 3) was investigated. The rearrangements were carried out in acetic anhydride containing about 1 0 / 00 sulfuric acid. Under these conditions acetoxy benzenium ions are formed as intermediates. These then undergo charge‐controlled [3 s , 4 s ]‐ and [1 s , 2s ]‐sigmatropic rearrangements. Thus, the [3 s , 4s ]‐process leads to the formation of the corresponding allenyl‐phenol acetates ( 19 , 21 , 23 , 25 , 28 , 30 ) whereas the [1 s , 2s ]‐process yields propargyl‐phenol acetates ( 20 , 22 , 24 , 26 , 29 ), respectively ( cf. scheme 4).