SYNTHESIS BASED ON CYCLOHEXADIENES .16. SYNTHESIS OF METHYL 2,7-DIMETHYLTRICYCLO[5.2.2.01,5] UNDEC-5-ENE-6-CARBOXYLATES

Synthesis of methyl 2, hyltricyclo{5.2.2.0(1,5}undec-5-en-6-carboxylat es, the tricyclic skeleton present in (+)-allo-cedrol (1) is described using the Diels-Alder strategy. Thus, Birch reduction of the aromatic acid 8 gives 5, the methyl ester of which is isomerised with DBU to a 1:1 mixture of the dienes 6 and 4. Cycloaddition of this mixture with 2-chloroacrylonitrile followed by hydrolysis yields the ketone 60 hav ing the tricyclo{5.2.2.0(1.5)}undec-5-ene framework. Similar reaction with methyl vinyl ketone affords the regioisomeric adducts 61 and 62.