Topochemical Selectivity in Solid-State Photorearrangement:  Conformational Control in Photorearrangements of cis-1,2-Dibenzoylalkenes

Solvent-Free Organic Synthesis

“…Photorearrangement of the cis -1,2-dibenzoylalkane derivative 324 in the solid state and in MeOH solution gave 326 and 325 , respectively, via ketene intermediates ( K1 and K2 ) . This indicates that the anti-syn form 324b and syn-anti form 324a exist predominantly in the solid state and in MeOH, respectively.…”

“…118 Photorearrangement of the cis-1,2-dibenzoylalkane derivative 324 in the solid state and in MeOH solution gave 326 and 325, respectively, via ketene intermediates (K1 and K2). 119 This indicates that the anti-syn form 324b and syn-anti form 324a exist predominantly in the solid state and in MeOH, respectively. Upon solid-state photoirradiation, the β-cyclodextrin complex of benzyl phenyl sulfone (327) undergoes a intramolecular rearrangement yielding o-methyldiphenyl sulfone (328) selectively, while, in solution, dibenzyl is obtained as the major product.…”

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

“…1,4a,b,5 However, in our work with 5,6-dibenzoyl-4-methoxybicyclo[2.2.2]oct-5-en-2-one (1) such migration was observed to occur from both the benzoyl groups in solution, whereas in solid state, only the expected vinylketene (1K) was identified. 6 In all of these cases the intermediate vinylketenes have so far been neither isolated nor characterized fully because of their instability. The vinylketene 1K was found to be fairly stable in cyclohexane solution at 20 °C.…”

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

“…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.…”