ABSTRACT
About 40 years have passed since methylene dizinc reagent was discovered as a substitute for Wittig reagent. Density functional theory (DFT) calculations have been performed to understand the reaction pathways of methylenation of carbonyl compounds with bis(iodozincio)methane. The present computational/theoretical study concluded that the methylenation reaction with gem-dizinc reagent proceeds as a two-step reaction, that is, methylene addition (RDS) and olefination. In the first step, the nucleophilic attack of the CH2 group enhanced by two Zn proceeds under the assistance of the electrophilic activation of the carbonyl group with the Zn atom. In the second step, the olefination is facilitated by both Zn atoms of the gem-dizinc reagent without an electron transfer process.
Subject(s)
Methane/analogs & derivatives , Aldehydes/chemistry , Alkenes/chemistry , Carboxylic Acids/chemistry , Indicators and Reagents , Ketones/chemistry , Methane/chemistryABSTRACT
Bis(iodozincio)methane, prepared from diiodomethane and zinc, reacts with an organic halide in the presence of a transition-metal catalyst to give an iodozinciomethylenated compound; this then reacts with another organic halide to form a C--C bond. The overall process connects two electrophiles with one carbon atom. Bis(iodozincio)ethane can also undergo this transformation, yielding a new stereogenic center. The asymmetric induction of this stereogenic center was investigated by using a chiral palladium catalyst.
Subject(s)
Hydrocarbons, Halogenated/chemistry , Methane/analogs & derivatives , Palladium/chemistry , Catalysis , Methane/chemistryABSTRACT
Both enantiomers of 3-hydroxyalkanoates and -alkanones were prepared by the diastereocontrolled addition of enolates to ketones containing (R)-6-methyl-1,3-oxathiane moiety as a chiral auxiliary; a formation of enolate from samarium(II) iodide and alpha-bromoamide is also discussed.
