Directed remote metalation

Directed remote metalation (DreM) of biaryl amides and O-carbamates, conceptually based on the complex-induced proximity effect (CIPE) [15] provides, especially in view of their link to transition metal-catalyzed cross coupling regimens [16], general and versatile routes to fluorenones (16 —> 15, Scheme 4) [5,17] and biaryl amides (16 —> 17) [18] whose features are overriding Friedel-Crafts reactivity and yield enhancement in comparison to Suzuki-Miyaura coupling routes for highly hindered biaryls, respectively. Additional features of the O-carbamate DreM result is potential further DoM of 17 with appropriate phenol protection and cyclization to dibenzopyranones [18]. 

The use of transition-metal arene complexes to facilitate nucleophilic aromatic substitution features in a route to derivatives of thiosalicylic acid and hence to thioxanthone. The cyclopentadienyl iron complex of 2-chlorobenzoic acid is converted into the benzamide prior to displacement of the chloride by thiophenoxide. Photolytic decom-plexation followed by directed remote metallation of the diaryl sulfide yielded the heterocycle (Scheme 207) <2000SL975>. 

Snieckus and Fu reported a new general and regiospecific synthesis of 9-phenanthrols involving direct ortho-metalation, Suzuki cross-coupling, and an LDA-mediated directed remote metalation sequence (Eq. (11)) [27]. 

Directed remote Metalation (DreM) in aromatics and heteroaromatics ... 

Beyond Do M The Directed Remote Metalation (DreM) of Biaryl Amides and O-Carbamates I 351... 

Synthetic Methodology Derived from the DoM-Cross-Coupling Nexus 11097 14.3.2.1 Directed Remote Metallation (DreM) Connections... 

Scheme 14.17 Directed remote metallation (DreM) strategies to condensed aromatics and heteroaromatics.

James, C.A. (1998) The directed remote metalation - Carbamoyl migration reaction. Total syntheses of the defucogilvocarcins and amottin 1 and synthesis of heteroarylfused benzopy-ranones. Ph.D. Thesis. University of Waterloo, Canada. 

FIGURE 26.8 Directed remote metalation (DreM) categories. 

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