Unexpected Solid-State Photochemistry of an α-Thiophenyl-α‘-Thiophenyl-S,S-dioxo-Substituted Ketone
journal contributionposted on 18.01.2008, 00:00 by Marino J. E. Resendiz, Jennifer Taing, Saeed I. Khan, Miguel A. Garcia-Garibay
Samples of 2,4-dimethyl-2-(thiophen-3-yl)-4-(thiophen-3-yl-S,S-dioxo)pentan-3-one 2 were obtained by controlled MCPBA oxidation of 2,4-dimethyl-2,4-di(thiophen-3-yl)pentan-3-one 1. Rather than the expected photodecarbonylation, UV−vis irradiation of 2 led to the intramolecular 2 + 2 photocycloaddition product 5 in quantitative yields (by GC and NMR) both in solution and in crystalline solid state. Detailed X-ray powder diffraction analyses revealed that the solid-state reaction of sulfone 2 occurs with a loss of long-range order despite retaining some birefringence under polarized microscopy.