Visible Light Induced Alkyl Cross-Coupling Reaction and Its Asymmetric Synthesis

Author:Zhou Quan Quan

Supervisor:xiao wen jing lu liang qiu

Database:Doctor

Degree Year:2019

Download:146

Pages:224

Size:16535K

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Sunlight is the most abundant and green energy on the earth,the organic synthesis reaction using visible light has the advantages of green,high efficiency,mild conditions and environmental friendliness.The organic synthesis reaction driven by visible light has been greatly developed in the past ten years and has become one of the important directions in the field of organic syntiiesis.At the same time,aliphatic compounds containing alkyl substitutions are found everywhere in nature and in living organisms,and are one of the basic structural units constituting organic chemistry.Therefore,the alkyl cross-coupling reaction has always been one of the hot topics in organic synthesis.Visible light induced photoredox catalysis has provided a new method for the mild generation and transformation of free radicals and showed certain advantages.The application of this strategy to the functionalization of alkyl carbon compounds will inevitably further expand the synthetic chemistry,In this dissertation,recent advances in this field were reviewed and some visible light induced alkyl cross-coupling reactions and asymmetric synthesis transformations were investigated.The detailed works were described as below:Firsts we chose the readily available carboxylic acids as starting materials and developed a photocatalytic direct radical decarboxylative alkynylation reactions.These reactions allow the preparation of various alkynes in good to excellent yields under mild conditions.More importantly,the uitilization of these reactions has been demonstrated in the derivation of naturally-occurred ursolic acid and the preparation of oxazolidinones.In additioi,a possible reaction mechanism was proposed based on a series of control experiments.Based on the decarboxylative alkynylation reactions,we reported a photoredox catalytic a-cyanation reaction of tertiaiy amines and decarboxylative cyanation of carboxylic acids using cyanobenziodoxols as a stable and safe cyanide source.This protocol is favored for mild conditions,the avoidance of extra oxidant and highly toxic cyano anion,good functional tolerance as well as safe and simple operations.By doing so,a various of α-aminonitriles and alkyl nitriles are afforded in good to excellent yields.Then,we further expand the alkyl cross-coupling reactions to alkenylation of unactivated alkyl bromides,silicone reagent(TMS)3SiH was used as atom transfer reagent to activate the alkyl bromides.Through two methods:photocatalytic alkenylation reactions of unactivated alkyl bromides with vinyl phenyl sulfones and dual photoredox and nickel-catalyzed alkenylation reactions of unactivated alkyl with vinyl bromides,a various of alkenes were synthesized from easily available feedstock with good reaction efiGciency and high chemoselectivity under mild reaction conditions.To further demonstrate the applicability of present strategy,the alkenylation of bioactive molecules and glycosyl bromides,as well as the alkynylation of unactivated alkyl bromides,were proven feasible.In addition,combined with visible light catalysis and organic catalysis mode,using oxygen as oxidant,we achieved dehydrogenation of saturated aldehyde under mild conditions.Further asymmetric β-functionalization of aldehydes by oxidation of enamines and their application in cascade reactions have also been developed.Finally,we have developed a new dual photoredox and nickel catalysis system for the asymmetric desymmetric C-O coupling reactions.The use of axially chiral 2,2’-bipyridime ligands was determined to be vital for the successful implement of this protocol,whieh produced a variety of chiral 1,4-benzodioxanes in good reaction efficiency and moderate to good selectivity.