Transannular Diels-Alder studies of 14-membered cis-trans-trans macrocyclic trienes having allylic ether or enone dienophile

Highly convergent, malonate alkylation based syntheses of the model macrocy cles and their title investigations are reported. In the allylic ether dien ophile case, a preference for tricycles with equatorial ether position was found at the transition state level. Ab initio calculations also show that the origin of this preference is not only steric but stereoelectronic as we ll. The enone dienophile case indicates that when the enone system is not t otally twisted out of planarity by the macrocyclic environment, the Diels-A lder reaction follows the usual trend in terms of dienophile activation. (C ) 2000 Elsevier Science Ltd. All rights reserved.