Controlled, Sequential approach to Synthesize Stereogenic Methanesvia in situGenerated Reactive Intermediates

Abstract

A facile and straightforward synthesis of unsymmetrical triarylmethanes and stereogenic methanes have been realized through the Friedel‐Crafts type alkylation of arenes with alkoxyaluminium intermediate generated in situ from aldehyde, arene and AlBr3 at room temperature in presence of catalytic quantity of AlBr3. This protocol is successful with diversity of starting materials and desired products were obtained in moderate to good yields. The displacement of ‐OAlBr2 with catalytic quantity of AlBr3 generated the reactive carbocation like intermediate which underwent subsequent reaction with another nucleophile (either ‐C, ‐S or –O nucleophile) and furnished the corresponding substituted products. The mechanism of the controlled, sequential reaction has been investigated by density functional theory calculations. Our model suggests that the involvement of penta coordinate complex in which the cleavage of C−OAlBr2 bond is favoured over N−AlBr2 bond at room temperature, in presence of additional catalyst.

Brønsted Acidic Ionic Liquid Catalyzed Three-Component Friedel–Crafts Reaction for the Synthesis of Unsymmetrical Triarylmethanes

“…): [33] CAS Number 2032423-57-5; 68% yield (0.2225 g) as a white solid; m.p. 178-180 °C; Rf = 0.10 (20% EtOAc/n-hexane);…”

Direct synthesis of completely unsymmetrical triarylmethanes via Fe(III) salt‐mediated in situ o‐quinone methides process

“…reaction in the presence of an acid catalyst, but poor regioselectivities were often obtained (Scheme 1a). [13][14][15][16][17][18][19][20][21][22][23][24] In recent years, a number of novel methods such as crosscoupling reactions [25][26][27][28][29][30] and C-H functionalization [31][32][33][34] have been developed. However, most of the reactions require expensive transition metals and ligands (Scheme 1b).…”

“…[ 10–12 ] The conventional method for the synthesis of unsymmetrical triarylmethanes is the Friedel–Crafts reaction in the presence of an acid catalyst, but poor regioselectivities were often obtained (Scheme 1a). [ 13–24 ] In recent years, a number of novel methods such as cross‐coupling reactions [ 25–30 ] and C–H functionalization [ 31–34 ] have been developed. However, most of the reactions require expensive transition metals and ligands (Scheme 1b).…”