Improved ethynylation of nitrocarbonyl derivatives by cerium trichloride assisted addition of ethynyl magnesium bromide

The addition of the Grignard reagent ethynyl magnesium bromide to nitroaryl carbonyls in the presence of cerium chloride was investigated. Thus, 2- and 4-nitrobenzaldehyde, 2- and 4-nitroacetophenone 2-nitrocinnamaldehyde and 1-aryl-3-aryl'-2-en-propanones (nitrochalcones 4a-g), gave alpha-ethynyl-2- and 4-nitrophenylmethanol 2a-b, alpha-ethynyl-2- and 4-nitrophenyl ethanol 2c-d, trans-1-(2-nitrophenyl)-1-penten-4-yn-3-ol (5) and trans-1-aryl-3-ar yl-1-penten-4-yn-3-ol 6a-g, respectively. It was found that in the absence of the lanthanide, the ethynylation reaction was a low yielding process.