The effect of electron donating groups on the stability of thiabenzenes

1-(p-Methoxyphenyl)-2,4,6-triphenylthiabenzene (X) has been synthesized and shown to be more stable than the 1-phenyl analog. 1-Phenyl-2,4,6-tri(p-methoxyphenyl)thiabenzene (XVI) was not stable enough to be isolated in pure form and rearranged readily to the isomeric 2-and 4-thiopyrans. Only the pure 4-phenyl-2,4,6-tri(p-methoxyphenyl)thiopyran (XVIII) could be isolated.