Cascade Reactions With Electron Deficient Enamines For The Synthesis Of Amidine,1,2,3-Triazole And Acetal Derivatives

Upon the current emphasis on green chemistry and environment protection,the demand in developing efficient,green and atom economical synthetic method keeps increasing.Electron deficient enamines such as enaminones,enaminoester etc.are a class of easily available and stable synthetic materials whose C=C double bond are capable of undergoing various electrophilic,nucleophilic and cyclization transformations,showing broad utilities in the synthesis of diverse organic compounds.The main contents of this thesis are enaminone/enaminoester-participated environmentally friendly cascade reactions for the synthesis of amidines,1,2,3-triazoles and functionalized acetals.Three main sections are included.The first section,catalyst-free synthesis of N-sulfonyl amidines is realized via enaminoester carbon-carbon bond cleavage reactions in pure water medium.The method is realized on N-sulfonyl amidine synthesis via the reactions of enaminoesters and tosyl azide without using any catalyst or additive in pure water medium.The chemo-selective N-sulfonyl amidine synthesis is realized via the major transformation of in situ[3+2]cycloaddition forming triazolines and the subsequent decomposition based on bond cleavage.The ester group in the enamine substrates turned out to play vital role in inducing the chemo-selectivity.The second section,Et₃N-catalyzed enaminoester-tosyl azide annulation for 1,2,3-triazoles synthesis in water.By employing Et₃N to catalyze the reactions ofβ-substituted NH-enaminoesters and tosyl azide,the efficient synthesis of full substituted1,2,3-triazoles is enabled.In addition,expanded research lead to the observation on the selective formation of N-alkyl sulfonamides when N-alkyl enaminoesters are used to react with tosyl azide under identical reaction conditions.The third section,the C-N bond and C=C double bond functionalization of enaminones is applied to the synthesis of functionalized acetals.The reactions of N,N-disubstituted enaminones and alcohols for the synthesis ofα-iodo-3-oxoacetals by the promotion of iodine are explored and established.The reactions featured with mild conditions and simple operation,disclosing new synthetic applications of enaminones.