Improved Julia−Kocienski Conditions for the Methylenation of Aldehydes and Ketones
摘要:
The scope of the methylenation of aldehydes and ketones under optimized Julia-Kocienski conditions is broadened by using 1-tert-butyl-1H-tetrazol-5-ylmethyl sulfone. Two different Barbier-type procedures are applied with NaHMDS at -78 degrees C or Cs2CO3 at 70 degrees C. The latter conditions are also adapted for the preparation of 1,2-disubstituted olefins and intramolecular olefination reactions.
Intramolecularly alkylated Costa complexes: New models for coenzyme B12 with a cobalt-to-ligand carbon bridge
作者:Bert van Arkel、Juul L. van der Baan、Sijbe Balt、Friedrich Bickelhaupt、Martinus W.G. de Bolster、Gerhard W. Klumpp
DOI:10.1016/0040-4020(95)00132-r
日期:1995.4
The synthesis of Costa-typeB12models 1 with a carbon bridge between the equatorial ligand and cobalt has been accomplished by condensation of butanedione monoxime and 2-(ω-functionalized)alkyl-1,3-diaminopropanes 8 followed by complexation with Co(II), introduction of a leaving group and intramolecular alkylation via Co(I) intermediates. The solution structure of intramolecularly alkylated Costa