Simple Synthesis of Amides and Weinreb Amides Using PPh₃ or Polymer‐Supported PPh₃ and Iodine

Abstract

The combination of PPh3/I2 has been shown to be effective for conversion of a range of carboxylic acids to 2°, 3°, and Weinreb amides. Simplification of the procedure was possible with the use of polymer-supported PPh3/I2. Weinreb amides produced via the use of polymer-supported PPh3 could be filtered through a short silica gel plug and used in further transformations. Thus, use of polymer-supported PPh3 offers potential applicability to diversity-oriented reactions. Formal total syntheses of apocynin and pratosine, as well as syntheses of anhydrolychorinone and hippadine, have been achieved via the use of this amide-forming method. An attempt has been made to gain insight into this reaction.

Activity patterns of metal oxide catalysts in the synthesis of N-phenylpropionamide from propanoic acid and aniline

“…Eqn (8) proves that the experimental 0th-order kinetic dependence depends on large values of the adsorption constant K 4 which means, in turn, an extensive coverage of the active sites by reagents, products, and/or intermediates. Eqn (8) proves that the experimental 0th-order kinetic dependence depends on large values of the adsorption constant K 4 which means, in turn, an extensive coverage of the active sites by reagents, products, and/or intermediates.…”

“…2 All such methods suffer from severe environmental, safety, and economic drawbacks, including the use of noxious and/or dangerous reagents, and multiple reaction-purification steps resulting in a poor atom economy, while large amounts of harmful waste, requiring special disposal treatments, contribute to high E-factors. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Apart from the recognized effectiveness of microwave irradiation on the condensation of carboxylic acids with amines, 4,6 and some catalytic redox routes using alternative reagents, 5,8,9,16 the most attractive option for amide bond formation is the heterogeneous catalytic condensation of amines with carboxylic acids. 2 On this account, the synthesis of amides has been recently indicated as a major green chemistry issue.…”

“…1,2 An alternative method involves the condensation of carboxylic acids with amines at high temperatures (>453 K), but is unfeasible for many functionalized substrates. [10][11][12][13][14][15] Many solid acids such as boron-organic compounds, 7 Fe 3+ /K10 montmorillonite, 10 FeCl 3 , ZnCl 2 , zeolites, and silica-based catalysts, 11 sulphatedtungstate, 12 MCM-41, 13 and Zr-salts, 14 were shown to be active in the synthesis of amides using toluene under "azeotropic distillation" reflux conditions (383 K), [1][2][3][4][5][6][7][8][9][10][11][12][13][14] while CeO 2 showed the highest activity among many oxides in various transamidation reactions. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Apart from the recognized effectiveness of microwave irradiation on the condensation of carboxylic acids with amines, 4,…”

Concise and Enantioselective Total Synthesis of (−)‐Mehranine, (−)‐Methylenebismehranine, and Related Aspidosperma Alkaloids

“…The penultimate step to the cyclization precursor (+)- 13 consisted of a lactam formation of amino acid (+)- 12 induced by triphenylphosphine–iodine. [13] An inverse addition under infinite dilution conditions increased (~25%) the yield by minimizing intermolecular condensation and allowed for the isolation of lactam (+)- 25 in 78% yield. Finally, a ring-closing metathesis of lactam (+)- 25 promoted by 2nd generation Hoveyda–Grubbs catalyst [14] at 80 °C afforded lactam (+)- 13 in 87% yield on gram-scale.…”

Progresses of Weinreb Amides in Organic Synthesis

“…早先, PPh 3 / CBr 4 组合已经用于 WAs 的制备 [15] . 2010 年, Kumar 等 [16] 报道了利用 [20] . 最近发现, 14 甚至可与血浆中的游离脂肪酸形成酰氟, 再与二甲胺反 应得到类 Weinreb 酰胺.…”