N,N-Dibutyl-2-p-tolyl-acetamide

Thionyl chloride (2.18 ml, 3.56 g, 30 mmol, 1.5 eq) was added dropwise to a vigorously stirred solution of p-tolylacetic acid (3 g, 20 mmol, 1 eq) and heated to 100°C for 3 hours. After cooling to room temperature, the volatiles were removed under reduced pressure [1]. The yellow residue was dissolved in 20 ml of dry ether and dibutylamine (11.1 ml, 8.28 g, 64 mmol, 3.2 eq.) was added dropwise at 0°C. After the addition was complete, the solution was allowed to warm to room temperature and stirred for 3 hours. The crude solution was washed with 2 x 25 ml of saturated NaHCO₃ solution and 2 x 25 ml of brime. The organic phase was dried over MgSO₄ and concentrated under reduced pressure. The crude product was purified by horizontal distillation (Kugelrohr) at 150°C (p=0.05 mbar) to yield 2.7 g (52 %) of the title product as a colorless oil.

IR (FT): 2958; 2872; 1642 (C=O); 1515; 1456; 1377.

¹H NMR (CDCl₃, 400 MHz): 7.13 (AB, J = 8.0, 2 H, H_arom); 7.11 (AB, J = 8.0, 2 H, H_arom); 3.64 (s, 2 H, CH₂); 3.31 (m, 2 H, NCH₂); 3.19 (m, 2 H, NCH₂); 2.31 (s, 3 H, CH₃); 1.24-1.56 (m, 8 H, 2xCH₂CH₂); 0.92 (t, J = 7.3, 6 H, 2xCH₃).

¹³C NMR CDCl₃, 100 MHz): 170.2 (S, C=O); 135.6 (S, C_arom); 132.4 (S, C_arom); 128.9 (D, J = 157, CH_arom); 128.3 (D, J = 157, CH_arom); 47.7 (T, J = 134, NCH₂); 45.3 (T, J = 134, NCH₂); 40.4 (T, J = 128, CH₂CO); 30.9 (T, CH₂); 29.5 (T, CH₂); 20.7 (Q, CH₃); 20.0 (T, CH₂); 19.8 (T, CH₂); 13.6 (Q, J = 126, CH₃).

Mass (CI, NH₃): 262 (100, [M+H]⁺); 156 (15, [CONBu₂]⁺); 105 (8, [M-CONBu₂]⁺).