Synthesis And Ring-opening Reactions Of Four-Membered Ring Compounds

The study of carbon-carbon bond formation and cleavage reaction of cyclic compounds is one of the core topics in organic chemistry.Although the four membered ring compounds with high tension are applied to the transition metal catalyzed carbon-carbon bond cleavage reaction,the ring opening reaction of highly functionalized four membered ring compounds is more challenging.The research work of this thesis has been focused on exploring the synthesis of alkylidenecyclobutenones and their reactivity in ring opening and ring expansion under the Lewis acid,palladium catalyzed ring-opening of 2-alkylidenecyclobutanols,andpalladiumcatalyzedenantioselectivering-opening/cross-couplingof cyclobutanones.Firstly,we focus on the synthesis of four-membered enones,polysubstituted alkylidenecyclobutenones.we described a[2+2]cycloaddition of ynamides and propargyl silyl ethers,which catalyzed by Lewis acid.This regioselective[2+2]cycloaddition enables efficient construction and conversion of four-membered enones,which provides structurally diverse products through unexpected ring-opening and ring expansion of alkylidenecyclobutenone with organolithium,Grignard reagents,water and primary amines.Secondly,we designed a facile synthesis ofγ,δ-unsaturated ketones.The key step of this palladium-catalyzed ring-opening of 2-alkylidenecyclobutanols with organic halides involves C_sp3-C_sp2 bond cleavage via palladium-catalyzedβ-carbon elimination.The desiredγ,δ-unsaturated ketones are obtained in good to excellent yields and broad functional group tolerability is observed.Thirdly,we focous on the asymmetric catalytic reaction invloved in cyclobutanones.Apalladium-catalyzedenantioselectivesequential ring-opening/cross-coupling of cyclobutanones is disclosed,providing chiral indanones bearing C3-quaternary stereocenters.In summary,These three types of novel reactions on the synthesis and transformations of four membered-ring compounds extended the content of four membered ring compounds and provided efficient methods for the synthesis and transformation of four membered ring compounds.