Abstract
This thesis describes the studies on intramolecular Diels-Alder reactions of masked o-benzoquinones, i.e., 6-alkenyloxy-4-bromo-6- methoxy-2-methyl-2,4-cyclohexadienones 101-104 and 6-alkenyloxy-4- bromo-6-methoxy-3-methyl-2,4-cyclohexadienones 105-108. Further, the adducts 59-66 obtained from these cycloaddition reactions were subjected to debromination and Stille coupling reactions using Pd-catalysts. The brominated masked o-benzoquinones 101-108 were generated n situ from the corresponding 2-methoxyphenols 35, 36 and alkenols 6a-26d. The intramolecular Diels-Alder reactions of 101-108 provided desired adducts 59-66 in high yields. The adducts 59-66 were debrominated via palladium catalysed selective hydrogenolysis to obtain the tricyclic compounds 28u-28ab. The overall yields of compounds 28u-28ab obtained via the present three-step methodology are much higher compared to the yields obtained in the earlier method from the corresponding masked o-benzoquinones27u-27ab without bromine substituent at C4 Stille coupling reaction of adducts 59-66 with tributylallyltin mediated by Pd(0) furnished the desired compounds 85-92 in excellent yieldso.