Diastereoselective cyclopropanation of ketone enols with Fischer carbene complexes.
Treatment of aryl/heteroaryl methoxycarbene complexes of chromium with -substituted ketone lithium enolates between -78 degrees C and room temperature resulted in the diastereoselective synthesis of 1,2,2,3-tetrasubstituted cyclopropanols. An exception has been observed in the reaction with cyclohexanone lithium enolate that yielded a bicyclic 2-buten-4-olide. 1,2-Dimethoxycyclopropanes and 1-methoxy-2-trimethylsilyloxycyclopropanes were isolated by quenching the reactions with MeOTf or Me3SiCl, respectively. This novel cyclopropanation process involves formation of lithium (3-oxoalkyl)pentacarbonylchromate intermediates which on warming undergo intramolecular addition to the carbonyl group. This cyclization is equivalent to the cyclopropanation in smooth conditions of electron-rich alkenes with Fischer carbene complexes.
Barluenga
José
J
Instituto Universitario de Química Organometálica "Enrique Moles" Unidad Asociada al CSIC, Universidad de Oviedo Julián Clavería 8, 33006 Oviedo, Spain. barluenga@uniovi.es
Suero
Marcos G
MG
Pérez-Sanchez
Ivan
I
Flórez
Josefa
J
D003500:Cyclization; D003521:Cyclopropanes / Q000737:chemistry*; D006838:Hydrocarbons / Q000737:chemistry; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D008094:Lithium / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D013237:Stereoisomerism
D003521:Cyclopropanes; D006838:Hydrocarbons; D007659:Ketones; D009942:Organometallic Compounds; C030011:carbene; D008094:Lithium; D008697:Methane