Studies On Cascade Reactions Based On The Alkynyl Difunctionalization

Difunctionalization of alkynyl in a single operation is much more atom and step economical by comparing with traditional synthesis.The difunctionalization of alkynyl group is presently one of the most attractive transformations in organic synthesis.By focusing on the alkynyl difunctionalization,the content of this thesis consists of four different sections.(1)Synthesis of 1,4-dihydropyridines via the multimolecular cascade reactions based on electron deficient alkynes.By activating the alkynyl esters with secondary amine,we have explored and achieved the multimolecular cascade reactions of alkynyl esters and primary amines toward the synthesis of 1,4-dihydropyridines.This method has exhibited good tolerance to the reaction of aryl amines,alkyl amines and ammonium acetate.(2)Electron deficient alkynes-based cascade cycloaddition reactions for the synthesis of benzaldehyde derivatives.Also by the secondary amine activation,we established the cascade [2+2+2] cycloaddition/aromatization reactions of alkynyl esters and enals under acidic conditions for the synthesis of poly substituted benzaldehydes,providing a new method on the o-aryl benzaldehyde synthesis.The reaction are performed in acetic acid which acts both as the medium and catalyst of the synthesis.(3)The Z-selective sulfonl halogenations reaction of alkynes.By using CuX(X= Cl,Br,I),sulfonyl hydrazines and terminal alkynes as starting materials,with the assistance of BPO,a class of Z-halovinyl sulfones have been synthesized via the key sulfonyl radical intermediate,and the products could be post elaborated to other derivative by means of classic coupling reactions such as Sonogashira coupling.(4)Copper-catalyzed hydrosulfonylation of alkynes.In the presence of copper catalyst,the BPO has been used as the radical initiator by heating at 70 oC in DMSO.The selective hydrosulfonylation of terminal alkynes has been realized by employing sulfonyl hydrazine as the sources of sulfonyl and hydrogen atom,by which a class of sulfonyl alkenes have been smoothly synthesized.