Dipolar Addition Reaction, Baeyer-villiger Oxidation, Phthalaldehydes Condensation Research Based On Carbene Chemistry

Carbenes are one of the most studied molecules in organic chemistry owing to theirparticular activity and performance in reaction, both metal-carbenes complexes or freecarbenes have their own unique value in research as well as application. In view of researchfocus and experience of our group in carbenes, three reactions, respectively involvedmetal-carbenes complexes as intermediate, metal-carbenes complexes as catalyst, freecarbenes as catalyst, were investigated. In this thesis, we conducted our work in followingthree sections:1) A practical system to synthesize the multiple-substituted2,5-dihydrofuran by theintermolecular dipolar cycloaddition reactions involving acceptor/acceptor diazo reagentsIntermolecular dipolar cycloaddition reaction of acceptor/acceptor diazo reagents,aldehydes, and acetylenedicarboxylate was investigated. Activity trend of differentacceptor/acceptor diazo reagents was given based on experiment study and theoreticalcalculation. The reactions proceeded effectively under ambient temperature with low reactantratios to produce2,5-dihydrofuran (yield up to89%,50:50<dr <95:5). This reaction has twocompetitive paths, one forms1,3-dioxolane and the other forms2,5-dihydrofuran. It’s foundbulk group substituted diazo reagents prefer the latter path.2) Baeyer-Villiger oxidation of cyclobutanones by achiral and chiral NHC-Pd complexesA series of chiral and achiral NHC-Pd complexes were synthsized. Achiral NHC-Pd cancatalyze the reaction in H2O (yield36%~91%). Substrates study showed that electron richcyclobutanones can get higher yield than electron poor ones. Currently available chiralNHC-Pd complexes gave excellent yield (64%~99%) but poor stereoselectivity (ee≤28%).To get good enantiomeric excesses, new chiral NHC ligand still needs to be designed andsynthesized.3) N-heterocyclic carbene catalyzed regioselectivity and stereoselectivity controllablecondensation of phthalaldehyde to produce polyhydroxylated fused indenonesThe N-heterocyclic carbene catalyzed condensation of phthalaldehyde produce pentatomic ring and hexatomic ring fused indenone. It was observed that both reactiontemperature and concentration of phthalaldehyde caused different distribution of two products.Under optimized condition, both typical electron rich and electron poor phthalaldehydesselectively gave hexatomic ring fused indenones. We proposed the reaction mechanism, andmade a conclusion that pentatomic ring fused indenone was dynamic product, another wasthermodynamic product.