THE MUKAIYAMA REACTION OF KETENE BIS(TRIMETHYLSILYL)ACETALS WITH α-HALO ACETALS - A CONVENIENT BUTENOLIDE SYNTHESIS
Ketene bis(trimethylsilyl) acetals were reacted with α-halo acetals giving β-alkoxy-γ-halo acids which were converted to butenolides by reaction with equivalents of base.This constitutes a novel and short butenolide synthesis.
Enediolates of carboxylic acids in synthesis: Synthesis of γ-chloro-β-hydroxy acids
Enediolates from carboxylic acids react readily with cyclic α-chloroketones to give the corresponding γ-chloro-β-alkoxycarboxylate intermediates depending on the ring size. Small ring ketones lead to γ-chloro-β-hydroxy acids in a highly stereoselective wa
Diastereoselective cyclopropanation of ketone enols with Fischer carbene complexes
Treatment of aryl/heteroaryl methoxycarbene complexes of chromium with β-substituted ketone lithium enolates between -78 °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. Copyright
Barluenga, Jose,Suero, Marcos G.,Perez-Sanchez, Ivan,Florez, Josefa
Ruthenium pincer-catalyzed synthesis of substituted γ-butyrolactones using hydrogen autotransfer methodology
The ruthenium pincer-catalyzed synthesis of γ-butyrolactones from 1,2-diols and malonates using borrowing-hydrogen methodology is reported. This regioselective domino-process takes place through catalytic C-C bond formation, followed by intramolecular transesterification. Herein, we show the Ru-MACHO-BH complex as a valuable catalyst in hydrogen autotransfer reactions.