Abstract
The dissertation is divided into two parts: Chapter I describes that a mild Pd/Cu-cocatalyzed radical cascade, proceeding via a sequence of Sonogashira coupling followed by [4 + 1] and [4 + 2] cycloadditions, has been developed to rapidly assemble cyclopenta[b]naphthalene and benzo[b]fluorene derivatives. In addition, a convenient and general approach for cyclopenta[b]naphthalene derivatives containing a structurally diverse functional group, including trimethyl silyl, aryl, ester, ketone, secondary/tertiary amide, phosphonate and halogen, at C-4 position has also been successfully developed, wherein Mn(III) plays a critical role to effect the oxidative tandem 5-exo-dig and 6-exo/endo cyclization efficiently. Finally, the total synthesis of natural products retrojusticidin B, justicidin E and helioxanthin, making use of a tandem free radical cyclization process mediated by Mn(OAc)3 as a key operation, has been concisely achieved in four or five steps in an overall yield of 45%, 33% and 44%. Charpter II describes that an efficient Cu(I)-catalyzed intramolecular cyclization of -activated carbonyl compounds has been developed, leading to 2,3,5-trisubstituted furans in good to high yields. The advantage of this synthetic method lies in its operational simplicity, mild reaction conditions and a wide scope of accessible substrates.