Solid-state photolysis of sterically congested cis-1,2-dibenzoylalkenes: isolation and characterization of vinylketenes

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

“…In unsymmetrical derivatives such migrations have been found to take place from the benzoyl group attached to the more crowded olefinic carbon atom to the less crowded one [23]. A similar observation has been reported from our laboratory for bicyclo [2.2.2]octenone systems [13]. Thus, selective formation of 10a,b is expected with the exception that the ketenes 10a,b were unusually stable.…”

“…The synthetic procedures, photochemical studies and spectra (UV, IR, mass, 1 H NMR, 13 C-NMR, DEPT-135) of all new compounds can be found in the Supporting Information File 1 and Supporting Information File 2.…”

“…Photochemical studies and spectra (UV, IR, mass, 1 H NMR, 13 The definitive version of this article is the electronic one which can be found at: https://doi.org/10.3762/bjoc. 16.190…”

“…For several years, our laboratory (S. Lahiri et al) is primarily engaged in synthesizing various types of such multichromophoric systems to compare their photochemistry in detail [9][10][11][12][13][14][15]. Since in acyclic enones like C, E/Z-photoisomerization becomes one of the major energy dissipation pathways, we selected rigid bicyclic multichromophoric enones like D to minimize this route.…”

“…Another interesting set of competitive 1,5-(C-O) acyl shift rearrangements (formation of vinyl ketene) with that of 1,2-AS were observed when photoreactions of bridged bicyclic systems like 3a-g were carried out [9][10][11][12][13]. These molecules contain a δ-keto-α,β-enone system juxtaposed with a (cis)-dibenzoylalkene moiety.…”