Switching the Mallory Reaction to Synthesis of Naphthalenes, Benzannulated Heterocycles, and Their Derivatives

Abstract

This review analyzes the new life of a long-known reaction, the photocyclization of diarylethenes, which became a classical tool for the synthesis of phenanthrenes and their heterocyclic analogues (Mallory reaction). It has been shown in recent years that certain diarylethenes undergo photorearrangement to naphthalenes, benzannulated heterocycles, or related products with bicyclic unit. Herein, I analyze how the Mallory reaction path can be altered to obtain bicyclic rather than tricyclic products. The mechanistic aspects and scope of the reaction are discussed.

Tandem Synthesis of 1,3-Disubstituted Naphthalenes via TfOH-Promoted Directed-Aldol and Friedel–Crafts Reactions

“…3 Therefore, great efforts have been made to develop efficient methods for the synthesis of aryl-substituted naphthalenes. 1,4 Prominent among the existing methods are intra-and intermolecular annulations between a (2-phenylethyl)carbonyl and a nucleophilic two-carbon partner. 5−7 Our attention was attracted by those Lewis acid-catalyzed intermolecular annulations using an alkyne as such a partner due to easy performance and accessible substrates.…”

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

“…The CH 2 Cl 2 extracts were combined, dried over Na 2 SO 4 , filtered and evaporated. The residue was subjected to column chromatography on silica gel using a mixture of CH 2 Cl 2 /hexane as eluent, to give the single aza [4]helicene with isolated chemical yields ranging from 71 to 99%. General procedure for the synthesis of diimine precursors: A solution (5 mL) of tris(dibenzylideneacetone)dipalladium(0) (0.013 mmol) and rac-BINAP (0.027 mmol) in tolune was purged with nitrogen, and stirred at 110 °C for 30 min.…”

“…The residue was subjected to column chromatography on silica gel using a mixture of CH 2 Cl 2 /hexane as eluent, to give the diimine precursor with isolated chemical yields ranging from 46 to 76%. General procedure for the synthesis of double aza [4]helicenes: A solution of precursor diimine (0.075 mmol), iodine (0.165 mmol), and propylene oxide (4.5 mmol) in 120 mL of toluene was irradiated in a photoreactor fitted with a water-cooled (8 o C) immersion flask and a medium-pressure Hg lamp (125 W) under N 2 atmosphere. After completion (24 h, monitored by TLC) toluene was evaporated under reduced pressure.…”

“…The CH 2 Cl 2 extracts were combined, dried over Na 2 SO 4 , filtered and evaporated. The residue was subjected to column chromatography on silica gel using a mixture of CH 2 Cl 2 /hexane as eluent, to give the double aza [4]helicene with isolated chemical yields ranged from 44 to 99%.…”

“…The photochemically produced cis isomer can undergo a further 6 π-electron cyclization process followed by oxidation to form phenanthrene. [1][2][3][4] This reaction was discovered in 1950. 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.…”