Selective Aromatic N‐Substitution with N‐(4‐Tolyl)hydroxylamine by Addition of Polar Aprotic or Diethereal Solvent

Abstract

Amination of anisole and toluene with N‐(4‐tolyl)hydroxylamine in trifluoroacetic acid was tuned to regioselectively provide the corresponding diarylamine by partial replacement of trifluoroacetic acid with a polar aprotic or a diethereal solvent. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Highly efficient and selective partial reduction of nitroarenes to N-arylhydroxylamines catalysed by phosphine oxide-decorated polymer immobilized ionic liquid stabilized ruthenium nanoparticles

“…A survey of the effect of the temperature revealed that the selectivity for N-phenylhydroxylamine decreased with an increase in the reaction temperature due to the formation of aniline. For example, when the reduction was conducted with three equivalents of hydrazine hydrate in ethanol at 50 °C using 0.1 mol% 2, N-phenylhydroxylamine was obtained in 88 % yield and selectivity together with 11 % aniline and a trace amount of azoxybenzene after 1 h; a further increase in the reaction temperature to 60 °C gave 70 % N-phenylhydroxylamine and 28 % aniline (Table 1, entries [14][15]. When the reaction temperature was reduced to 25 °C the high selectivity for N-phenylhydroxylamine (>99 %) was retained but the conversion dropped to 65 % after 1 h with an initial TOF of 1,040 mol product mol cat -1 h À1 ; gratifyingly though, complete conversion was obtained by increasing the reaction time to 2 h (Table 1, entry [16][17].…”

“…The synthesis of N-arylhydroxylamines is of considerable interest as they are important intermediates to high value products including pharmaceuticals such as acetaminophen and pyraclostrobin and bioactive derivatives of the antibiotics azomycin and chloramphenicol [1][2][3][4][5][6][7][8][9][10][11], fine chemicals [12][13][14], polymerisation inhibitors [15][16] as well as useful reagents in organic synthesis as they undergo cyclizations, rearrangements and metal-catalysed additions to multiple bonds [17][18][19][20][21][22][23]. While N-arylhydroxylamines can be prepared by metal catalysed Narylation of a hydroxylamine [24][25][26][27] or the catalytic reduction of aldoximines [28][29][30][31][32][33], the selective reduction of nitroarenes is potentially the most versatile and convenient [34][35][36][37][38][39][40][41][42][43][44][45]…”

Preparation of Substituted Phenanthridines from the Coupling of Aryldiazonium Salts with Nitriles: A Metal Free Approach

“…Spectral data of the compounds are in agreement with those reported in the literature. A typical procedure for preparing 2-( o -tolyl)-aniline is shown below …”

Nitrenium Ions and Problem of Direct Electrophilic Amination of Aromatic Compounds

“…The large absolute ρ + values for the N-and C-attack (-5.2 and -4.0, respectively) are consistent with participation of nitrenium ion in the rate-determining stage. Addition of polar solvents to TFA-PPA was found to increase the regioselectivity of amination of anisole and toluene with 4-tolylhydroxylamine [119]. The direction of amination of benzene with N-phenylhydroxylamine depends on the acidity of the medium [120].…”