1,2,3-Triphenyl isoindole

Cava and Schlessinger have reported the synthesis of 1,2,3-triphenyl-isoindole (65) in 78% yield from 1,3-diphenylisobenzofuran (68) hy reaction with thionylaniline (69) and boron trifluoride. The mechanism proposed for this remarkable transformation involves reaiTangement of the adduct (70) derived from thionylaniline and the isobenzofuran, to the tricyclic intermediate (71). This presumably collapses to the S-sultam (72), which yields the isoindole (65) upon extrusion of sulfur dioxide. Loss of sulfur dioxide, both from S-sultones and unsaturated S-sultams, is well documented. ... 

A photoperoxide in the isoindole series has been reported. Upon irradiation of a solution of 1,2,3-triphenyl isoindole (CXIX) in the presence of oxygen, 1,2,3-triphenylisoindole peroxide (CXX)285 is formed. 

Keywords 3,4-bis(diphenylmethylene)-iV-methylsuccimide, [4+2]photodimeri-zation cyclization, 2-methyl-4,4,9-triphenyl-3a,4-dihydro-benzo[f]isoindole-1,3-dione... 

Various routes to 1,1,3-trisubstituted 1//-isoindoles have been reviewed.5 Thus, the triphenyl derivative 53 is available from the reaction of benzo-phenone imine with diphenyldichloromethane or by the Friedel-Crafts reactions between benzene and l,l,3-trichloro-lf/-isoindole. Recently, another route, which involves heating the cyclotriphosphatriazene 54 with benzophenone, has been described.86 The nitrone derivative 55 of the isoindolenine 53 may be obtained by treating the isoindolenine with m-chloroperbenzoic acid. This nitrone has also been obtained by the isomerization of the oxaziran 56 in the presence of a Lewis acid (Scheme 11).87... 

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