The syntheses of 2,3,5-trimethylidenebicyclo[2.2. Ilheptane (1) and 2,3,5,6,7-pentamethylidenebicyclo[2.2.2]-octane (2) are reported. The Diels-Alder additions of the diene moieties of these polyenes can be regioselective, probably because of a possible transannular interaction between the homoconjugated methylidene and s-cis-butadiene groups.Introduction. -The Diels-Alder regioselectivity of an exocyclic diene4) grafted onto bicyclo[2.2. llheptane and bicyclo[2.2.2]octane skeletons can be controlled by remote substitution of the bicyclic systems [3-51. The ability of the homoconjugated methylidene group at C(5) in triene 1 to induce a 'para") regioselectivity was used in one [4] of our doubly-convergent syntheses of anthracyclines [5] [6]. We report here on the synthesis of 1 and on its Diels-Alder reactivity toward several dienophiles. We report also on the synthesis of the exocyclic pentaene 26). The homoconjugative interactions invoked to
showed exciton-split type of Cotton effects attributed to through-space interactions between the s-gauche-butadiene and s-cis-butadiene chromophores of these systems.
ChemInform Abstract Baker's yeast reduction of the readily available ketone (I) under fermenting conditions stereospecifically affords the bicyclo(2.2.2)octanol (IIIa). Its mesylate (IIIb) is hydrolyzed rearranging with high stereoselectivity to the bicyclo(3.2.1)octanol (VIa). Analogous reactions are carried out starting from racemic (IIIa) which is obtained by NaBH4 reduction of (I). The absolute configuration of (IIIa) is deduced from the CD spectrum of its derivative (IIIc) applying the chiral exciton-coupling method. The CD spectra of (VIa) and its silyl ether (VIb) are likewise studied in detail.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.