Abstract
Chapter I-Part 1 In the first portion, we report a new hydrative cyclization of triynes to afford bicyclic spiro alcohols, which undergo subsequent dehydration to give bicyclic ketones. This platinum catalysis is proposed to comprise a sequence of cascade reactions including: two selective hydrations, alkyne insertion and aldol condensations. Chapter I-Part 2 In the second portion, we report one-pot synthesis of tetracyclic ketones via PtI2-catalyzed hydrative cyclization of trialkyne functionalities. These triyne substrates bear an electron-rich aryl group at the outer alkyne to direct the initial hydration occurring at the adjacent alkynyl carbon. This tandem catalysis is proposed to comprise two alkyne hydrations, an alkyne insertion and an intramolecular aldol condensation. Chapter I-Part 3 In the third portion, we report one-pot synthesis of benzopyrone derivatives from PtCl2-catalyzed hydrative carbocyclization of oxodiynes. This hydrative carbocyclization proceeds through sequential oxo-assisted hydration of two tethered alkynes to give oxo-dione intermediates, followed by intramolecular aldol reactions and aromatization. The substrate with an ester group can undergo platinum-catalyzed hydrative cyclization to yield the precursor of Arnottin I in moderate yield, which is helpful to synthesize this kind of nature products. Chapter II In this chapter, we report a platinum-catalyzed aromatization of trialkyne functionalities bearing both benzene and bridging cyclohexenyl group via intra- and intermolecular nucleophilic additions to form chrysene derivatives efficiency. The importance of this cyclization is reflected by its extension to the synthesis of novel polyaromatic compound. This tandem cyclization is proposed to comprise a Bergman-type cyclization, an alkyne insertion and a hydrodemetalation. 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. Thermal cyclization proceeded only with 3,5-dien-1-ynes bearing an electron-withdrawing C(1)-phenyl or C(6)-carbonyl substituent. On the basis of this structure-activity relationship, we conclude that such a [1,7]-hydrogen shift is characterized by a “protonic” hydrogen shift, which should be catalyzed by π-alkyne activators. To achieve the atom economy, we have developed a tandem aldol condensationdehydration and aromatization catalysis between cycloalkanones and special 3-en-1-yn-5-als using the weakly acidic catalyst CpRu(PPh3)2Cl, which provided complex 1-indanones and α-tetralones with good yields in most cases.