Abstract
Abstract This dissertation describes development of new synthetic organic transformations by using transition metal catalysis. The use of gold and rhodium metals enables mild, diastereoselective and efficient transformations of variety of readily available substrates to wide range of synthetically useful nitrogen and oxygen containing heterocyclic products. For convenience and better understanding, this thesis is divided into four chapters. The first chapter describes the two new formal cycloaddition reactions between nitrosobenzenes and alkenylgold carbenoids. We obtained quinoline oxides in good to better yields from the gold-catalyzed [3+3]-cycloadditions between nitrosobenzenes and alkenyldiazo esters. For propargyl esters, its resulting gold carbenes react with nitrosobenzene to give alkenylimine, followed by a [4+2]-cycloaddition with nitrosobenzene to form 1, 2-oxazines. The second chapter deals with the development of an oxa-Povarov reaction/carbene generation sequence for alkenyldiazocarbonyl compounds. A triflic acid catalyzed reaction of vinyl diazoacetate with diphenoxymethylbenzene to give diazo-containing cycloadducts stereoselectively with fruitful range of substrate scope. The dihydrobenzopyran core moiety found in many natural product and bioactive molecules. The third chapter explains, the gold-catalyzed reactions between vinyldiazo carbonyl species and acetals to obtain selectively E-configured alkyl 3,5-dimethoxy-5-pent-2- enoates in good yields. According to our experimental data, this reaction sequence involves an initial Prins-type reaction, followed by gold-carbene generation. The success of this Prins-type reaction indicates a stabilization effect of the diazo functionality on the adjacent carbocation. The fourth chapter provides gold-catalyzed oxa-Povarov reactions involving readily available diaryloxymethylarenes and aryl-substituted alkenes to give dihydrobenzopyrans; their [4+2]-cycloadditions are efficiently catalyzed by gold catalysis with high diastereoselectivity. The cycloadditions were applicable to broad range of substrate under ambient conditions. Product analysis reveals that the reaction likely proceeds via a stepwise ionic mechanism because both E- and Z-configured β-methylstyrene gave the same cycloadducts in the same proportions.