Proton-Catalyzed Hydroamination and Hydroarylation Reactions of Anilines and Alkenes:  A Dramatic Effect of Counteranions on Reaction Efficiency

Abstract

Acid-catalyzed additions of amines to alkenes are generally unsuccessful due to the buffering effect of the amine substrate. 1 Friedel-Crafts alkylations of arylamines are hindered by coordination of the amine to the Lewis acid catalyst. 2 A recent communication by Hartwig et al. reports that several common Brønsted acids catalyze the intramolecular hydroamination of tosyl-protected amino olefins. 3 Beller and co-workers have reported that alkylations of electron-rich anilines with styrene are promoted with HBF 4 ·Et 2 O. 2b,4 Herein we report the first homogeneous 5 acid catalyst that promotes both hydroamination and hydroarylation reactions of anilines and alkenes, including simple cyclic alkenes and dienes. These transformations are air-and moisture-tolerant and can be controlled to favor either N-H or Ar-H addition products based on reaction conditions and aniline substitution pattern. The key to the activity of this system is that the acid counteranion has a dramatic effect on reaction efficiency.In the course of our studies on metal-catalyzed hydroamination reactions, 6 we found that Ph 3 CB(C 6 F 5 ) 4 (1) catalyzes the reaction of norbornene with aniline. Both hydroamination (2) and ortho-hydroarylation (3) products are formed using 5 mol % of 1 (eq 1). 7(1)

Montmorillonite K-10: An efficient and reusable catalyst for the synthesis of quinoxaline derivatives in water

“…The result suggest that Mont K-10 provide a suitable strength of the Brønsted acid sites which required for the efficient condensation reaction of 1,2-diamine with 1,2-dicarbonyl compounds, and prevents the neutralization by the basic diamine, when compared with sulfamic acid acids. Furthermore, the two-dimensional silicate sheets of Mont K-10 provide wide spaces for the catalytic reaction, and effectively act as the macro counter anions to decrease their anion coordination ability toward the H + site [25], leading to high activity for generation of carbocation intermediate.…”

Gold versus Silver‐Catalyzed Intermolecular Hydroaminations of Alkenes and Dienes

“…When different amides such as sulfonamides and carbamates were allowed to react with norbornene (1a) in the presence of [(PhO) 3 P]AuCl/AgOTf or simple AgOTf as catalysts, only electron-rich sulfonamides were appropriate nucleophiles for this HA ( Table 2, entries 1-7). The HA with p-toluenesulfonamide (2a) worked with both Au and Ag catalysts, but a higher loading must be used in the latter case ( Table 2, entries 1 and 2).…”

“…Several Brønsted acids, such as triflic acid, [2] PhNH 3 BA C H T U N G T R E N N U N G (C 6 F 5 ) 4 , [3] proton-exchange montmorillonite, [4] silicotungstic acid, [5] phosphomolybdic acid supported on silica gel [6] and SO 3 H-functionalized ionic liquids [7] have been used for the intermolecular hydroamination of olefins and conjugated dienes. Iodine [8] and Nbromosuccinimide [9] have been recently employed for the addition of sulfonamides [8,9] and carbamates [9] to vinylarenes.…”

“…Similar considerations can be made when metal salts or complexes are used as catalysts. BiA C H T U N G T R E N N U N G (OTf) 3 /[CuA C H T U N G T R E N N U N G (CH 3 CN) 4 ]PF 6 for 1,3-dienes, [10] CuA C H T U N G T R E N N U N G (OTf) 2 /dppe for styrenes, norbornene and cyclohexa-1,3-diene, [11] FeCl 3 for styrenes, [12] InBr 3 , [13] ZrA C H T U N G T R E N N U N G (OTf) 4 , [14] and Pt(II) complexes activated by AgBF 4 [15] for acyclic and cyclic alkenes have also been used in HA reactions. Other homogeneous catalysts, such as alkali metal amides, [16] lanthanides, [17] and early (Ti, Zr) transition metals [18] work mainly with amines forming metal-amide and metal-imide intermediates in the last case.…”

“…Silver triflate gave 98% yield using the same conditions as with [(PhO) 3 P]AuCl/AgOTf (Table 1, compare entries 10 and 11). The loading of the gold catalyst formed by [(PhO) 3 P]AuCl/AgOTf could be decreased to 0.1 and 0.05 mol% providing 3aa in high yields. However, with only 0.01 mol% loading the yield dropped down to 60% (Table 1, entries 12, 13, and 15).…”