Studies On C-C And C-O Coupling Based Onα-Position Of α-Oxo Ketene-(S,S) Acetals

α-Oxo ketene-(S,S)acetals are versatile intermediates in organic synthesis andhave been widely applied in the construction of a diverse array of polysubstitutedcarbo-and heterocyclic compounds. After a hundred years of development, thechemistry of α-oxo ketene-(S,S)acetals has become an important research topic inorganic chemistry.α-Oxo ketene-(S,S)acetals are valuable substrates with a variety of chemicalproperties owing to their structural diversity. The highly polarized push (dialkylthiogroup)-pull (electron-withdrawing group) interaction on the C C double bond ofα-oxo ketene-(S,S)acetals makes their α-carbon atom a potential nucleophilic center,and the coupling reaction at the nucleophilic α-carbon atom of these β,β-dialkylthioactivated alkenes is reliable and incorporates a wide variety of carbon and heteroatomelectrophiles. As an important property of α-oxo ketene-(S,S)acetals, in recent yearswe have realized halodecarboxylation, halodeacetylation, Baylis-Hillman reaction,Michael addition, acetylation, coupling reaction with alcohols, multi-componentreaction, etc. and has made great advances in the construction of a diverse array ofpolysubstituted carbo-and heterocyclic compounds, such as cyclohexanones,unsymmetrical biaryls, benzofurans, coumarins, pyridines, indolizines, indoleN-oxides, etc.The C C bond forming reaction and carbon heteroatom bond coupling areimportant research contents in organic chemistry. The exploration of newcarbon carbon and carbon heteroatom bond forming reaction on α-C of α-oxoketene-(S,S)acetals has been the chief goal of our research. This thesis will show somenew exploratory work in this field and mainly includes three aspects:1. Copper(II) bromide catalyzed C C coupling reaction of benzylic alcohols withα-Oxo ketene-(S,S)acetals have been realized, and we have developed a convenientsynthesis of polyfunctionalized4H-chromenes and dihydrocoumarins from the easilyavailable ketene dithioacetals and2-(hydroxymethyl)phenols. The protocol iscontrolled through the choice of solvents or the reaction time and features mildreaction conditions, high yields and multifunctionality of products.2. Pd(OAc)2catalyzed direct coupling reactions of α-oxo ketene-(S,S)acetalswith carboxylic acids in the presence of PhI(OAc)2as an oxidant has been realized,and a new synthetic method for alkenyl esters was developed. α-Alkenoyl-α-acetoxy ketene-(S,S)-acetals, products of these C O coupling reactions, are good Nazarovcyclization substances, experimental results demonstrate that the α-alkenoyl groupsignificantly affects both the reactivity and products of the Nazarov cyclization.3. An efficient synthesis of allylic sulfones via a threee-component reactioninvolving an α-oxo ketene-(S,S)acetal, an aldehyde and4-methylbenzenesulfinicacid was developed. It is the first example of sulfonylmethylation of activatedalkenes.