A SYNTHETIC APPROACH TO 11-OXABICYCLO[6.2.1]UNDECYL BICYCLICS

Through a sequence of reactions including Diels-Alder cycloaddition of a furan diene as the key step, 11-oxatricyclo[6.2.1.0(1,6)]undecyl ri ngs were synthesized from 5-methylfurfural with the goal of developing a synthetic protocol to 11-oxabicyclo[6.2.1]undecyl system. The strat egy to incorporate an oxygen atom at C6 carbon of tricyclic 11 or 16 b y Baeyer-Villiger oxidation was unsuccessful, implicating that there i s too much steric congestion around the carbonyl ketone. As an alterna tive approach, bicyclic 23 and 24 were prepared from 2-methylfuran via known tricyclic 20. Cyclization of bicyclic 23 and 24 under several r eaction conditions also failed to produce hydroxylated product 25 and 26.