Pyridine Derivatives Served As Organocatalysts For Organic Reactions

This thesis focuses on pyridine derivatives served as organocatalysts for organic reactions.It is well-known that the interest in the field of organocatalysis has increased spectacularly in the last few years. One hand, N-oxides are able to mediate an astonishingly wide variety of transformations both as organocatalysts and ligands. Pyridine N-oxide is the basic fragment of chiral N-oxides. However, rare report utilizing pyridine N-oxide as a catalyst in organic reactions appeared. On the other hand, pyridinium tribromide (PTB) was usually used as a bromination reagent, and is more convenient to handle than bromine.It has been also reported that PTB could server as a catalyst in the aziridination of olefins.However, few example utilizing PTB as a catalyst in organic reactions were reported.Aziridines have attracted increasing attention as versatile building blocks and important precursors for the synthesis of many nitrogen-containing biologically interesting molecules.In part one, we studied the ring-opening reactions of aziridines with thiols utilizing pyridine N-oxide as organocatalyst. The results show that pyridine-N-oxide serves as an efficient catalyst for the ring-opening reactions of N-tosylaziridines with various aryl thiols under mild conditions. This transformation is highly effective, which gives rise to the correspondingβ-amino sulfides in good to excellent yields. We also investigated the mechanism of this reaction and proposed that pyridine N-oxide may act as a nucleophilic trigger during the reaction process.The bisindolylalkane derivatives belong to an important class of compounds. Continuous attention has been paid to the synthesis of bisindolylalkanes under different conditions.In the second part of this thesis, we described that pyridinium tribromide(PTB) was an efficient catalyst for the synthesis of bis(indol-3-yl)alkanes in ethyl acetate at room temperature.The method tolerated a wide variety of aldehydes, indoles, and limited amount of ketones. The catalyst is inexpensive and easily available.