Study On Allylations In Aqueous Media And Theorectical Study On The Mechanism Of Wacker-type Oxidative Cyclization

This thesis was made up of two sections: the study on the methodology of allylations in aquous media and the theoretical study on the mechanism of Pd-catalyzed Wacker-type oxidative cyclization.Organic reaction in aqueous media is a significant branch of green chemistry. Barbier-type carbonyl allylation in water is largely studied because of its potential application in organic synthesis and convenient performance in technology.Firstly, in this dissertation the recent research of the organometallic reactions in aqueous media were reviewed.Secondly, a novel mediator (Sn/I₂) was developed and employed in the allylation and crotylation of various aldehydes and ketones with allyl (crotyl) halide in water. The reaction could proceed smoothly to give the desired product in high yield. Compared to the prior reports, the reaction can be carried out using allylic chloride instead of allylic bromide in the system, and it is a simple, efficient synthesis method. The regioselectivity and diastereoselectivity were also studied. Sn/I₂ promotes the allylations of aldehydes with crotyl bromide to give dominantγ-adducts with minorα-isomers while Sn/I₂ promotes the reaction with crotyl chloride to give dominantα-adducts with minorγ-isomers.Thirdly, Indium, tin and bismuth nanoparticles successfully mediated crotylation of various carbonyl compounds with crotyl halides in water to afford the corresponding homoallylic alcohols in good to quantitative yields in a short time respectively. The reaction activity, regioslectivity and diastereoselectivity of crotylation reaction could be influened by different nano-metals. Indium nanoparticles promoted the allylations of aldehydes and inactive ketones with crotyl bromide or chloride to give exclusiveγ-adducts with dominant syn-isomers. Tin nanoparticles promoted the allylations of carbonyl compounds with crotyl bromide, and gave mostγ-adducts with dominant anti-isomers. Bismuth nanoparticles promoted the allylations of aromatic aldehydes with crotyl bromide, to give mostγ-adducts with dominant syn-isomers.Recently, quantum computational chemistry has become an important tool to investigate chemical problems. It helps chemists resolve the problems which are difficult or inaccurate in experiments. In this thesis, the basic principle and theory of quantum chemistry were simply introduced. Then, computational method was used to explore the mechanism of the Pd-catalyzed Wacker-type oxidative cyclization which involves an usual 1,4-hydride migration. Theoretical studies showedβ-hydride elimination is thermodynamically unfavorable in the system whileδ-hydride elimination is thermodynamically favorable despite its high activation energy. The further study with microsolvation mold showed theδ-hydride elimination is dynamically feasible. It is remarkable that all these theoretical computations are in excellent agreement with the experimental observations and give a deep insight into the stereoselectivity and regiochemistry in the palladium(II) catalyzed Waker-type process.