SYNTHESIS BASED ON CYCLOHEXADINES .10. SYNTHESIS OF -7-METHOXY-4-OXATRICYCLO[4.3.1.0(3,7)]DECAN-2-ONES

Synthesis of 5, 5-dimethyl- 7-methoxy-4 -oxatricyclo[4,3,1,0(3,7)]- de can-2-one 3a, a novel heterocyclic ring system present in morellin 1, and its 3-substituted derivatives 3b-e, is described from the Diels-Al der adducts 7, available from 1-methoxycyclohexa-1,4-dienes 4. Two rou tes, which involved the halocyclisation and the oxidative addition, we re investigated for the conversion of the adducts 7 into 3. While the halocyclisation method resulted in mixtures, excellent yields of the t arget molecule were obtained by the second method. Solvolysis of the b romoether 9 resulted in a mixture of rearranged products 10, 13, 15 an d 16.