As a part of my Bachelor's thesis a series of aldehydes were converted into
corresponding geminal dibromoalkenes via first step of the Corey-Fuchs reaction, also
known as Ramirez olefination. Ice cold aldehyde solutions in dichloromethane were treated
with the ylide, which was formed in situ from tetrabromomethane and triphenylphosphine.
Subsequently, the aldehydes were converted into corresponding gem-dibromoalkenes.
We have successfully synthesised seven (het)aromatic 1,1-dibromoalkenes from the
starting aldehydes, two of which were monohalogenated benzaldehydes, two were
sterically hindered, one contained an electron-accepting and the other electron-donating
functional group, and one was a heteroaromatic aldehyde. The products were isolated,
purified by silica gel column chromatography and characterized by 1H NMR and IR
spectroscopy. The purity of the synthesized products was determined by HPLC
chromatography and the melting points of the solid products were also determined.
Comparison of the conversions of different substrates revealed that most of the aldehydes
were readily converted into the desired products.
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