The pyrolysis of 3-methyl-1-pentyn-3-ol (I) in acetic anhydride and in the presence of $p$-toluenesulphonic acid has been again investigated. The reaction, that takes place through the corresponding acetate II, affords a complex mixture of products, the main components being (Z)-3-methyl-3-penten-1-yne (Z-IV) and (E)-3-methyl-3-penten-2-one (E-V). On the basis of previous literature reports and new experimental findings, a reasonable mechanism for the conversion of Z-IV to E-V is proposed: in this context the stereochemistry of the Rupe rearrangement is also discussed.
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Con il contributo del Ministero per i Beni e le Attività Culturali