Side Products Formed in Trace Amounts

SCHEME 1.160 Formation of 1-ethynyl-l-cyclohexanol in the reaction of cyclohexanone oxime and acetylene in superbase media. 

SCHEME 1.161 Trace formation of -terphenyl in the reaction of acetophenone oxime with phenylacetylene in the system NaOH/DMSO. 

Earlier, the adduct of DMSO with acetophenone C has been isolated and characterized as hydroxy derivative (after neutralization of the reaction mixture) [340]. In more active superbase system KOH/DMSO (140°C, 4 h), the yield of p-terphenyl increases to 14.6%. 

The assumption that 1,3,5-triphenylbenzene is formed via trimerization of phenylacetylene has not been confirmed. Also, it cannot be formed as a result of autocondensation of oxime or ketone. Hence it follows that 1,3,5-triphenylbenzene is a minor product of the synthesis of pyrrole from acetophenone oxime and aphenylcetylene. 

SCHEME 1.162 Plausible scheme of / -terphenyl formation from acetophenone in the MOH/DMSO systems. 

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