Palladium-Catalyzed Ring Expansion Reaction of (Z)-1-(1,3-Butadienyl)cyclobutanols with Aryl Iodides. Stereospecific Synthesis of (Z)-2-(3-Aryl-1-propenyl)cyclopentanones
摘要:
A novel type of cascade ring expansion process has been developed by the palladium-catalyzed reaction of (Z)-1-(1,3-butadienyl)cyclobutanols with aryl iodides. The reaction proceeds in a stereospecific manner to produce (Z)-2-(3-aryl-1-propenyl)cyclopentanones. It has also been found that regioselective alpha-arylation of alkenyl cyclopentanones proceeds to afford the alpha-arylated cyclopentanones.
A concise and enantioselective approach to cyclobutanones by tandem asymmetric epoxidation and enantiospecific ring expansion of cyclopropylidene alcohols. An enantiocontrolled synthesis of (+)- and (-)-.alpha.-cuparenones
摘要:
A tandem Katsuki-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-alpha-cuparenones (11).
an oxidative ring expansion with Co(acac)2 and triplet oxygen to give 1,2-dioxanols. The formation of an alkoxy radical drives the regioselectivecleavage of the ring on the more substituted side before insertion of molecular oxygen. The reaction is particularly effective on secondary cyclobutanols but works also on certain tertiary alcohols. Further substitution with neutral nucleophiles under catalytic