Abstract
Chapter I In this chapter, cis-2,4-diene-1-al functionality are readily available in organic synthesis. To pursue the synthetic value of cis-2,4-diene-1-al, we report a novel gold-catalyzed deoxygenated cyclization of cis-2,4-diene-1-al via regiocontrolled 1,4-addition of two nucleophiles, which allows formation of two C-X bonds (X = H, O, S, N, C) on the newly generated cyclopentene framework. Notably, this approach enables a one-step construction of complex polycyclic frameworks via diversified annulation of cis-2,4-diene-1-al with suitable nucleophiles. Chapter II In this novel gold catalysis, the dication equivalence of cis-2,4-diene-1-al enables diversified version to construct complex framework. So far, we described the intermolecular versions of cyclization deoxygenated reaction. At this point we turned our attention to apply this newly developed reaction to its intramolecular version. We further extended this catalytic cyclization in presence of nuclophiles as trapping reagent, intramolecular cyclization proceeded smoothly to give complex oxacyclic compounds. One remarkable, We have successfully applied our novel intramolecular cyclization protocol for constructed Brazilin skeleton. This synthesis started by synthesis diene-aldehyde substrate, and based on intramolecular cyclization establish B/C ring junction successful synthesis Brazilane and Brazilane derivatives naturally. Chapter III Chapter III describes the feasibility of thermal and catalytic cyclization of 6,6-disubstituted 3,5-dien-1-ynes via a 1,7-hydrogen shift. We first studied the thermal efficiency of model molecules via alternation of the C(1)-phenyl and C(6)-carbonyl substituents of substrates; we concluded that the observed 1,7-hydrogen shift is nearly a “protonic” hydrogen shift. This structure-activity relationship indicates that □-alkyne activators can catalyze suitably functionalized 3,5-dien-1-ynes efficiently although their thermal yields were generally low. We prepared various 6,6-disubstituted 3,5-dien-1-ynes bearing either a phenyl or carbonyl group, and found their thermal cyclizations to be greatly enhanced by PtCl2, AuCl3, Ru-complex catalysts to confirm our hypothesis: the C(7)-H acidity of 3,5-dien-1-ynes is crucial for thermal cyclization.