Photochemistry of Stilbenes. II. Substituent Effects on the Rates of Phenanthrene Formation

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

“… 655 − 657 This intermediate tends to spontaneously undergo a subsequent oxidative dehydrogenation to yield a phenanthrene derivative. 656 − 658 However, in the absence of an oxidant, the dihydrophenanthrene intermediate may reversibly open to give the corresponding Z -stilbene; alternatively, if suitable substituents are present, hydrogen-shift processes may occur. 659 , 660 However, the presence of substituents such as methoxy 661 − 663 or halide 663 , 664 groups in the 2-position resulted in thermal non-oxidative elimination to form a phenanthrene derivative 114 ( Scheme 31 ).…”

Photoinduced Dispersibility Tuning of Carbon Nanotubes by a Water‐Soluble Stilbene as a Dispersant

“…It is known that, upon UV light irradiation, trans‐stilbene transforms into phenanthrene in a good yield as a photocyclization product in the presence of a suitable oxidant such as dissolved molecular oxygen 12, 13. The UV‐vis absorption spectral changes for 1 in H 2 O upon UV (365 nm) light irradiation for several hours are shown in Figure 1b.…”

Synthesis of azahelicenes through Mallory reaction of imine precursors: corannulene substrates provide an exception to the rule in oxidative photocyclizations of diarylethenes

“…5 However, it was poorly understood and remained obscure until Mallory postulated the reversible formation of the dihydrophenanthrene intermediate that could be oxidized to the fully aromatic structure. [6][7][8] This work demonstrated the need for an oxidant. Mallory established that a catalytic amount of iodine was key to the synthesis.…”

“…It is this practicality that allows for daunting synthetic targets to be prepared through Mallory reaction. This can be seen in Bunz's N-heteroarene, 10 Morin's graphene nano-ribbons, 11 Matsuda's [7]helicene, 12 Durola's double [7]helicene, 13 Fujita's [16]helicene, 14 Nuckolls hexabenzocoronenes, 15 Mallory's phenacenes, 16 Autschbach, Crassous, and Réau's metallahelicenes, 17 and corannurylene pentapetalae 18 syntheses employing the photochemical reaction as a key component in the construction of complex aromatic scaffolds. Despite this success, application of stilbene imines as precursors to prepare aza-based aromatic scaffolds is not feasible (Scheme 1).…”

“…The fate of the photochemical reaction in 5 is the same as 1 and 3 and 6 could not be obtained. Caronna and coworkers have shown that a naphthalene-based imine (7) could not be cyclized to 8 under neutral conditions. 22 In addition, azobenzene, having both olefin carbon atoms replaced with nitrogen atoms (N=N), is also not known to cyclize under Mallory conditions.…”