Studies And Applications Of The Ring Fragmentation Of 1, 3-Dithiolancyclopentyl In α-Oxo Cyclicketene-(S, S)-Acetals

Since Kelber first synthesized theα-benzoyl ketene (S, S)-acetal in 1910,α-oxo ketene (S, S)-acetal chemistry has become an important area in organic chemistry after a hundred years of development. Particularly, in the recent three decades, many papers have been published in this area, and several reviews were reported to summarize these results.Among the variousα-oxo ketene (S, S)-acetals,α-oxo cyclic ketene (S, S)-acetals are easier to prepare and bear much more functionalities. Generally, the reaction types involovingα-oxo cyclic ketene (S, S)-acetals mainly include the regioselective addition-aromatization with organometallic reagents, conjugate addition-cyclization with nitrogen nucleophilic species, nucleophilic reactions ofα-carbon, acting as odorless dithiol equivalents in thioacetalization and Michael additions, as well as the synthetic applications based on the above reactions. But the ring fragmentation of 1, 3-dithiolancycolpentyl moiety of ketene (S, S)-acetals was rarely reported. Therefore, studies and applications of the ring-opening reaction of 1, 3-dithiolancycolpentyl moiety should be a valuable research project.Developments of new basic reactions and new synthetic methods are the basis for the innovation and advance of organic chemistry. Based on the research achievement of our group inα-oxo ketene (S, S)-acetal chemistry in the past fifteen years. My work is based on the synthesis ofα-oxo cyclic ketene (S, S)-acetals, to develop new basic reactions and new synthetic methods for interesting ring-opening reaction of 1, 3-dithiolancycolpentyl, particularly, developing a new synthetic strategy to provide a general and simple route toα-functionalized thioamides and multisubstituted thiophene derivatives. At the same time, starting from theα-oxo cyclic ketene (S, S)-acetals to synthesize multisubstituted thiophene, investigations were also carried out on the reaction mechanish, through intramolecular thia-anti-Michael addition. In addition in the present of TBAB in water,α-oxo ketene (O, S)-acetals are synthesized simply and effectively. The contents in this thesis mainly include three aspects.1. Investigate the ring-opening of 1, 3-dithiolancycolpentyl inα-oxo cyclic ketene (S, S)-acetals in the presence of aliphatic primary amines and synthesize a rang of usefulα-functionalized thioamides.2. Design and synthesis of newα-oxo cyclic ketene (S, S)-acetal acylamides. In the presence of aliphatic amines we research the ring-opening reaction of its 1, 3-dithiolancycolpentyl moiety and gain multisubstituted thiophene derivatives. In the reaction we found a case of intramolrcular anti-Michael addition toα,β-ethylenically-unsaturated enones, in which an intramolecular thio-anti-Michael additions ofα-alkenoyl cyclic ketene (S, S)-acetals could occurred in the presence of amines, allowing the formation of five-membered sulfur-containing heterocycles. It has shown the weakening the ability of electronic withdrawing of carbonyl group in the enone systems is an efficient strategy for an anti-Michael addition.3. In the present of TBAB in water, through changing the reaction conditions such as the feed-type, we successfully preparedα-oxo ketene (O, S)-acetals in one-pot starting from active methlyene compounds and reacting with CS2, bromoethanol. The synthesis method is simple and effective, which is a foundation of green synthesis and applications ofα-oxo ketene (O, S)-acetals chemistry.