p-Toluenesulfonic acid (48 mg, 0.25 mmol) was added to a stirred mixture of ethyl 2-methyl-acetoacetate (1) (346 mg, 2.40 mmol) and a-methylbenzylamine (2) (358 mg, 2.95 mmol) in toluene (13 mL) [1]. Then a Dean-Stark trap device was fit and the reaction refluxed overnight. The mixture was allowed to reach room temperature and percolated over a silica gel pad and the solvent evaporated under reduced pressure to yield the title compound 3 (540 mg, 2.32 mmol, 96%).
IR (neat, cm-1): 3250 (N-H), 3062, 3027, 780, 702 (Ph), 1646, 1250, 1121 (COOEt), 1598 (C=C–N).
1H NMR (300 MHz, CDCl3): δ= 1.30 (3H, t, J=7.1 Hz, CH3CH2O); 1.50 (3H, d, J=6.9 Hz, H-2’); 1.75* (3H, s, Me-2); 1.78* (3H, s, H-4); 4.16 (2H, dq, J=7.1, 1.0 Hz, CH3CH2O); 4.64 (1H, quint, J=6.9 Hz, H-1’); 7.18–7.35 (5H, m, Ph); 9.66 (1H, br d, J=6.9 Hz, NH).
*These signals may be interchanged.
13C NMR (75 MHz, CDCl3): δ= 171.10 (C-1); 87.70 (C-2); 159.00 (C-3); 15.75 (C-4); 12.54 (Me-2); 14.63 (CH3CH2O); 58.73 (CH3CH2O); 53.17 (C-1’); 25.17 (C-2’); 145.75 (C-3’); 125.44 (C-4’, C-8’); 128.65 (C-5’, C-7’); 126.80 (C-6’).
EI-MS (70 eV, m/z): 248 (M++H, 7%); 247 (M+, 14); 232 (M+–Me, 2); 218 (M+–Et, 0.7); 202 (M+–OEt, 3); 186 (4); 174 (M+–COOEt, 5); 145 (15); 105 (C8H9+, 100); 79 (10); 77 (10); 42 (13).
Supplementary materials
Supplementary File 1Supplementary File 2Supplementary File 3Acknowledgement
We wish to thank the Ministerio de Ciencia y Tecnología for financial support (R+D Project PPQ2000-1665) and the Ministerio de Educación, Cultura y Deporte for a fellowship to J. M. Castro.
References
- Nour, M.; Tan, K.; Jankowski, R.; Cavé, C. Easy access to optically active Hagemann’s esters. Tetrahedron: Asymmetry 2001, 12, 765–769. [Google Scholar] [CrossRef]
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