Photochemical Generation and Reversible Cycloaromatization of a Nine-Membered Ring Cyclic Enediyne

Abstract

Irradiation of the nine-membered ring enediyne precursor, which has one of its triple bonds masked as cyclopropenone, efficiently (Phi = 0.34) generates the reactive 4,5-benzocyclonona-2,6-diynol. The latter rapidly equilibrates with the corresponding 1,4-didehydronaphthalene diradical and then undergoes rate-limiting hydrogen abstraction to produce the ultimate product of the Bergman cyclization, benz[f]indanol.

The thermal C2–C6 (Schmittel)/ene cyclization of enyne–allenes – crossing the boundary between classical and nonstatistical kinetics

“…[8][9][10] Their extraordinary reactivity and cytotoxicity have sparked considerable research and a great deal of efforts are being spent up to date to study the various factors influencing the Bergman cyclization. [11][12][13][14][15][16][17][18][19][20] In comparison with the pristine enediyne antitumor antibiotics cited above, neocarzinostatin (NCS) [21] although belonging likewise to the group of natural enediyne antitumor antibiotics contains a slightly different active chromophore, a dienediyne. [22] Like the natural enediynes, NCS shows a remarkable antitumor activity that is based on a related diradical cyclization.…”

1,2-Bis(dibromomethyl)benzene

“…For the preparation of the title compound, see: Ghorbani-Vaghei et al (2009). For its applications, see: Chen et al (2002Chen et al ( , 2006Chen et al ( , 2007; Chow et al (2005); Jansen et al (2010); Pandithavidana et al (2009); Swartz et al (2005). For related structures, see: Kuś & Jones (2003); Qin et al (2005); Sim et al (2001).…”

“…The title compound and its derivatives are useful reagents to build a naphthalene ring (Chen et al, 2002(Chen et al, , 2006(Chen et al, , 2007Chow et al, 2005;Jansen et al, 2010;Pandithavidana et al, 2009). In addition, they have been prepared as potential precursors to pentacene derivatives (Swartz et al, 2005).…”

A convergence of photo‐bergman cyclization and intramolecular chain collapse towards polymeric nanoparticles

“…Later, Turro and Nicolaou revealed that simple artificial enediynes could also undergo cycloaromatization upon photo‐irradiation 45. Subsequently, plenty of arene‐fused or nonbenzenoid, locked or acyclic enediynes were explored and investigated under photoirradiation 46–56. Photo‐Bergman cyclization was deemed to be similar in mechanism to that of the thermal induced.…”