Lifetimes of 1,5-biradicals formed from triplet o-alkoxy ketones

Stereoselective Synthesis of <i>cis</i>-Substituted-3’-anilino-2’, 3’-dihydro-4-2’-benzo[<i>b</i>]furanylcoumarins via Intramolecular Aldol Reactions

“…Hence only few methods are reported for the synthesis of stereo specifically enriched dihydrobenzofurans [27]. Although there are several photochemical approaches available for the synthesis of the dihydrobenzofuranol skeleton [28][29][30][31][32][33][34]. All the methods yield trans and cis products.…”

Photoredox Reactions of Quinones

“…A radicalclock study identified the lifetime of 1,5-biradical 102 to be 1-2 ns, [12d] which is approximately one order of magnitude smaller than that from ab enzophenone analogues. [36] Thus, 102 is rapidly converted to zwitterion 103 via electron transfer. An additional kinetic study revealed the influence of the size of the C2 substituent.…”

“…When 104 was exposed to air during workup, the hydroquinone underwent air oxidation to the anthraquinone, and the labile acetal was hydrolyzed. A radical clock study identified the lifetime of 1,5‐biradical 102 to be 1–2 ns, which is approximately one order of magnitude smaller than that from a benzophenone analogues . Thus, 102 is rapidly converted to zwitterion 103 via electron transfer.…”

A facile synthesis of dihydrobenzofuranols by photocyclization of (2-alkoxy-5-methyl-phenyl)(aryl) methanone and ethyl 2-aroyl-4-methylphenyloxyacetates

“…Among the compounds, benzophenones have been extensively studied from a viewpoint of reaction mechanisms and synthetic applications [4][5][6]. Photocyclization reactions of ortho alkoxy benzophenones and its derivatives proceed via 1,5-biradical intermediates formed through δ-hydrogen abstraction by the excited carbonyl group.…”

“…In the literature, there are few examples that discuss in detail solvent and substituent effects on cyclization of 1,5-biradicals [9,10]. In fact, Wagner et al have studied that photocyclization of 2-benzyloxybenzophenone and 2-benzyloxy acetophenone derivatives in nonpolar solvent like benzene, and revealed high stereoselectivity of cis isomer [5,6]. However, in the presence of Lewis base solvents stereoselectivity decreased markedly [4,6].…”