2- and 3-substituted thiophenes: some new reactions

Photolysis of a methanol solution of 2-(5~methoxy-thienyl)-diphenylcarblnol (IV) with ultraviolet light led to the formation of 5-diphenylmethylene-2(5H)-thiophenone (VI). The ketal-like structure VII has been proposed1 as an intermediate in this conversion. The carbinol, IV, containing 5^ oxygen-18 was prepared and converted by the photoreaction into VI. Mass spectral analysis showed that approximately half of the amount of labeled oxygen in IV had been incorporated into VI. A discussion has been presented concerning the possible conversion mechanisms of IV into VI based on spectroscopic evidence and mass spectral analysis.