Synthesis of 2-Norzizaene and 9,10-Dehydro-2-norzizaene (7,7-Dimethyl-6-methylidenetricyclo[6.2.1.01,5]undec-9-ene) via Intramolecular Allyl Cation Induced Cycloaddition

7,7-Dimethyl-6-methylidenetricyclo6.2.1.0^1,5]undec-9-ene ( 10 ) has been prepared from allylic alcohol 8 in one step in 16% yield. Selective hydrogenation of 10 with diazene gives the 2-norzizaenes 1a and 11 .