Studies On Some Tandem Reactions Involving Allene Intermediates

Sequential reaction represents an efficient and elegant way to access novel and complex molecules from simple and readily available starting materials. It is routinely employed to construct core skeletons of many important natural products now. Without isolating the intermediates, adding reagents or changing the reaction conditions, these reactions often allow an economically and ecologically favorable chemical process which is well appreciated in modern synthetic chemistry. Thus tremendous attention has been paid to the development and application of sequential reaction nowadays.Intrigued by the concept of sequential reaction and the remarkable advance on allene chemistry, in this dissertation we focus our attention on novel and interesting sequential reactions via allene intermediates for the rapid synthesis of structurally diverse polycyclic molecules. The whole work can be divided into five parts.1. We reported novel palladium-catalyzed sequential reactions utilizing an allene-intermediate-involved intramolecular [3+2] cycloaddition as the key step, resulting in a very facile and efficient method for the preparation of polycyclic pyrrole derivatives and indolin-2-ones from electron-deficient vinyl iodides and propargyl ethers.2. We developed an interesting sequential reaction consisting of Sonogashira coupling, propargyl-allenyl isomerization, allenyl-benzyl Claisen rearrangement and [4+2] cycloaddition. This reaction provides an efficient synthesis of fused tricyclo[3.2.1.02’7]oct-3-enes from electron-deficient vinyl iodides and1-aryl propargyl trityl ethers.3. We developed a facile and moderate-yielding method for the preparation of polycyclic isoindoline derivatives via tandem Pd-catalyzed coupling, propargyl-allenyl rearrangement,[4+2] cycloaddition and aromatization reaction starting from easily accessible starting materials. This method would be potentially useful due to a general lack of simple and efficient procedures for synthesis of these compounds in the literature. 4. We reported an interesting sequential reaction involving sequential palladium(O)-catalyzed decarboxylation of diynylic carbonates, intramolecular nucleophilic cyclization and Schmittel reaction, which provides a facile method for the synthesis of a variety of polycyclic benzo[b]fluorene derivatives.5. We developed a gold(I)-catalyzed reaction of homopropargyl azides for the synthesis of substituted quinolines. A plausible mechanism was proposed to rationalize the reaction.