Reaction of Carbonyl Compounds with Ethyl Lithiodiazoacetate. Studies Dealing with the Rhodium(II)-Catalyzed Behavior of the Resulting Adducts

Article abstract of DOI:10.1021/jo00300a035

The carbenoid intermediate derived by treating ethyl 2-diazo-4-phthalimidobutyrate with rhodium(II) octanoate undergoes transannular cyclization onto the adjacent imido carbonyl group.The resulting cyclic carbonyl ylide diploe was trapped with several dipolarophiles.In an attempt to prepare related substrates for cyclization studies, the reaction of ethyl lithiodiazoacetate with various aldehydes and ketones was studied.Treatment of the α-diazo-β-hydroxy ester derived from acetone or cyclopentanone with rhodium(II) octanoate gave rise to a β-keto ester.The exclusive phenyl shift encountered with acetophenone is in keeping with migration to an electron-deficient center.The reaction works well with acrolein, leading to high yields of 3-oxo-4-pentenoate.The 1,2-hydrogen shift pathway was found to proceed much faster than intramolecular cyclopropanation.Dehydration of the α-diazo-β-hydroxy esters generates vinyl diazo esters, which readily cyclize to 1H-pyrazoles on thermolysis.