Zwitterions In Carbon-Carbon And Carbon-Heteroatom Bond-Forming Reactions

"Zwitterions" is used to describe the inner salts with two parts of electric charges viz., the positive charge and the negative charge in the same one molecular (or intermediate). Generally, they are also denoted by common term as "dipoles". The present thesis is aimed at describing the detailed studies on zwitterions in carbon-carbon and carbon-heteroatom bond-forming reactions. It mainly consists of the following three parts:1. The investigation progress of zwitterions in carbon-carbon and carbon-heteroatom bond-forming reactions.The review summarizes the history of zwitterions in organic chemistry. On the one hand, the reaction of ylides, which are the zwitterions with positive charge and the negative charge on the two neighbor atoms, has been reviewed. It mainly focuses on the reactions of the most widely used ylides in organic chemistry viz., phosphonium, ammonium and sulfonium ylides. On the other hand, the carbon-carbon and carbon-heteroatom bond-forming reactions of the zwitterions formed from the addition of organic nucleophiles to activatedπ-systems have also been reviewed. These reactions are summarized according to different nucleophiles viz., phosphine nucleophiles, nitrogen nucleophiles and carbon nucleophiles.2. The investigation on the addition and cyclization reaction of activated olefins/alkynes catalyzed by 1,4-diazabicyclo [2.2.2] octane (DABCO).We have investigated the cyclization reaction ofα-halogen substituted alkanes, ketones and nitriles with various electrophilic olefins or alkynes for the formation of polysubstituted furan, dihydrofuran, 2H-pyran,γ-butyrolactone and cyclopropane derivatives catalyzed by DABCO via ylide mediated step. On the base of this research, we have also extended the catalyst to the reaction of alcohols, phenols, acylamides, acids, 1,2-diols, 1,2-diamines or amino alcohols with activated alkynes. A series of addition and cyclization products can be obtained. The results of our detailed investigations are presented here. It includes the design of the reaction, the selection of the condition, the scope and the stereoselectivity control of the reaction and the confirmation of the structure etc.3. The investigation on zwitterions in the reaction of cyclohexyl isocyanide with activated olefins.We have investigated the reaction of cyclohexyl isocyanide with activated olefins for the synthesis of 5-Hydroxy-2H-pyrrol-2-one derivatives. The protocol has also been extended to a multicomponent reaction of cyclohexyl isocyanide with various aldehydes and 1,3-dicarbonyl compounds catalyzed by piperidine. Herein, we will describe the full details of our research.