RICHTER-WIDMAN-STOERMER

RICHTER - WIDMAN STOERMER Cinnoline Synthesis Synthesis of cinnolines from substituted anilines via diazonium salts. 

REIMER TIEMANN Phenol formylation 314 REISSERT-GROSHEINTZ FISCHER Cyanoamme reaction 315 REPPE Acetylano reaction 3t6 von RICHTER Aromatic carboxylalion 317 von RICHTER - WIDMAN - STOERMER Cmndme synthesis 3t8 RILEY Selenaim dioxide oxidation 319 Rimmi 4... 

This approach is important for the synthesis of cinnolines. CHEC(1984) <1984CHEC(2)1> already covered several examples. The methodology used starts with an aniline ortho substituted with an alkene (Widman-Stoermer type), alkyne (Richter type), or enolisable ketone (Borsche type) which is diazotisized, delivering the sixth atom, allowing cyclization. CHEC-II(1996) <1996CHEC-II(6)1> gave more examples. 

With certain active methylene compounds, particularly with active methinyl compounds, diazonium salts may couple to form azo compounds. Several intramolecular couplings of diazonium salts with ortho substituents bearing an active methylene group give rise to cinnolines, a class of cyclic azo compounds (the Borsche, von Richter, and Widman-Stoermer syntheses.)... 

Cinnolines are prepared by an intramolecular cyclization of o-alkenyl or o-alkynyl aryldiazonium salts. For instance, (o-aminophenyl)alkynes 6 or alkyl(o-aminophenyl)ketones 8 (via the enol form) yield 4-hydroxycinnolines 7 (the v. Richter and Borsche syntheses, respectively), o-Aminostyrenes 10 afford 3,4-disubstituted cinnolines 11 (Widman-Stoermer synthesis) ... 

This reaction is related to the Widman-Stoermer Synthesis and von Richter Cinnoline... 

The Borsche (or Borsche-Herbert) cinnoline synthesis constitutes the cyclization of an ort/zo-diazonium aryl ketone to form a 4-cinnolone, or 4-hydroxycinnoline. It is mechanistically related to the Widman-Stoermer and Richter cinnoline syntheses, which involve the cyclization of ortho-diazonium aryl olefins and ortho-diazomnm aryl alkynes, respectively. 

The cinnoline ring system was first prepared by Richter via diazotization and subsequent cyclization of o-aminophenylpropionic acid. Subsequent efforts by Widman, and later Stoermer, demonstrated access to the cinnoline ring system via subjection of o-vinyl anilines to diazotization conditions. Other than the observation by Stoermer that o-aminocinnamic acid does not undergo cyclization when exposed to diazotization conditions, initially, little attention was paid to the influence of Ri and R2 on the cyclization of 1 to 2. Sixty years after Widman s first disclosure, Simpson and Schofield " began to address the role of Ri and R2 vide infra). There is a remarkable dearth of literature featuring the title reaction beyond the efforts of Simpson and Schofield, owing, in part, to many other useful methods to prepare cinnolines. 

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