Studies On The Ultraviolet Light Induced Cycloaddition Reaction Of Divinylbenzenes Derivatives

Natural products,drugs or other bioactive organic compounds usually have complex polycyclic structure or multi-functional groups.There are many traditional ground thermochemical methods for the synthesis of complex cyclic compounds,but photocycloaddition reactions are effective synthetic methods for compounds with specific polycyclic structures or many functional groups with more stereo center among numerous synthetic methods of polycyclic compounds.The photocycloaddition reaction is broad,encompassing the synthesis of three-to eightmembered rings in its common implementation and offering tremendous scope for stereo-control and substrate range.So photocycloaddition reactions have provided effective methods in the total synthesis of natural products or other bioactive unnatural compounds.Based on the importance of the photocycloaddition reaction we devoted to finding new methods for the synthesis of complex polycyclic compounds,such as benzobicyclo[2.2.2]octane skeletons and oxa-bridge ring structure compounds,via the design and synthesis of novel organic molecules and the exploration of a series of new photochemical reaction experiments.In this thesis,a series of divinylbenzenes derivatives were designed and synthesized in order to study the photoinduced [4+2] reactions of substituted odivinylbenzenes with olefins such as maleimide.This thesis disclosed such an efficient,transition-metal-free and environmentally friendly way for the rapid construction of benzobicyclo[2.2.2]octane skeletons at mild conditions.This approach,with a medium pressure mercury lamp with Pyrex as the light source,with dry acetonitrile as solvent,provides a novel access to synthesize benzobicyclo[2.2.2]octane skeletons in good yield(52-86%).The scope of substituted of divinylbenzenes derivatives were explored on the influence of the substituent.Experimental study shows that substrates containing ester group,aldehyde group,acetyl group,benzoyl group or cyano group underwent smoothly.On the basis of the experimental results and some literatures,the most plausible mechanism pathway was proposed.Under UV-light irradiation,o-divinylbenzenes underwent a pericyclic reaction to form the cyclic o-quinodimethane intermediates which were subsequently reacted with olefins through [4+2] addition to construct the benzobicyclo[2.2.2]octane skeletons.Gram scale reactions demonstrated the synthetic potential application of this protocol.This thesis disclosed such an efficient,metal-free,and environmentally friendly way for the rapid construction of complicated oxacyclic skeletons from divinylbenzenes derivatives containing carbonyl group through photoinduced intramolecular oxa-[4+2] cycloaddition with a 350 nm UV-light irradiation and dry acetonitrile as solvent to synthesize oxa-bridge ring skeletons in good yield(45-84%).Some control experiments were conducted to trap the reactive intermediate of this reaction,and results revealed that o-divinylbenzenes underwent a pericyclic reaction to form the cyclic o-quinodimethane intermediates which were subsequently reacted with carbon-oxygen double bond through intramolecular oxa-[4+2] cycloaddition to construct the complicated oxacyclic skeletons.Gram scale reaction demonstrated the synthetic potential application of this protocol.O-formyl styrene compounds can occur [1,5]-hydrogen migration and can form high activity of diene intermediates under ultraviolet light.A series of o-formyl styrene compounds was synthesized and the photoinduced [4+2] cycloaddition reactions were tested.The 2-(4-phenylbuta-1,3-dien-1-yl)benzaldehyde compounds can occur the intramolecular [4+2] photocycloaddition through ketene methide intermediate under the ultraviolet light.This reaction can be used to obtain benzobicycloheptanone compounds with good yields,which is a novel method for the preparation of benzobicycloheptanones compounds.This paper studies the mechanism of this reaction and the amplification experiments.At the same time,the photoproducts of benzobicycloheptanones can also be obtained via [2+2] photocycloaddition,so this two photocycloaddition reactions provide novel and effective methods for the synthesis of benzobicycloheptanones.