Infrared spectroscopic detection of ketene formation from carbene and CO source: amide synthesis
Synthesis and transformation of ketene into desired organic molecule is one of the methodologies widely used in synthetic organic chemistry, however there are only few reports available for the detection of ketenes (not free ketene but ketene complex of transition metal complexes) by using expensive techniques. Nevertheless, there is no report available to detect the ketene directly. In this regard we have developed a methodology to make amides via ketene formation by using diazo compounds, [Co2(CO)8] as a carbonyl source and suitable amines, and detected the ketene formation with the help of IR spectroscopy. The non-gaseous carbonyl source, [Co2(CO)8] mediated carbonylation of ethyl 2-diazo-2-phenylacetate produced ketene as key intermediate. The transformation of ketene to amide has been achieved by the nucleophilic addition of amine. We have also taken an effort to detect the formation of ketene intermediate from the reaction between ethyl 2-diazo-2-phenylacetate and [Co2(CO)8] in the absence of nucleophile. The IR spectroscopy revealed the formation of ketene followed by the transformation of ketene to amide by further addition of amine. The progress of the reaction has been monitored with function of time by using IR spectroscopy. Furthermore, all the newly synthesized amides have been fully characterized by using standard spectroscopic and analytical techniques.