Conclusions
In conclusion, in this work the chemical behaviour of phenylacetaldehyde was thoroughly investigated in multicomponent reactions with primary or secondary amines and various azides. The benzylamidines obtained proved to be useful intermediates in heterocyclic synthesis through a straightforward intramolecular condensation. Indeed starting from amidines 1d-f,i and 5b,c a new pyrrol-3-ones series were synthesized.
Experimental Section
General Procedures. Mps were determined by a Büchi 510 (capillary) apparatus. IR spectra were measured with a JASCO IR Report 100 instrument (Nujol; cm-1). NMR spectra were obtained with Bruker Advance 300 and Varian Gemini 200 spectrometers in CDCl3 solution at 25 °C, unless otherwise stated. J values are given in Hz. Low-resolution MS spectra were recorded with a Thermo-Finnigan LCQ ADVANTAGE AP electrospray/ion trap equipped instrument using a syringe pump device for the direct injection of sample solutions. 4-[3-(2- iodophenyl)-5-phenyl-4,5-dihydro-3H-1,2,3-triazol-4-yl]morpholine 4a2d is a known compound.
General procedure for the reaction of phenylacetaldehyde with tosylazide and primary or secondary amines
The selected amine (10 mmol) was dissolved in 20 ml of CH2Cl2 and 7 g of 4Å molecular sieves were added to the solution. Phenylacetaldehyde (10 mmol) and, after 30 min., 10 mmol of tosyl azide were added to the reaction mixture. The solution was stirred at room temperature for 12 h until disappearance of the starting materials (TLC: ethyl acetate/cyclohexane 1:1). The resulting suspension was filtered and evaporated. The crude product was purified by column chromatography (ethyl acetate/cyclohexane 1:1). When primary amines were used as reactants, two main fractions were collected containing 2-benzyl-N-alkyl-N'-tosyl-amidine 1 and N-alkyl- N'-tosyl -formamidine 2, respectively. Starting from secondary amines, only formamidine 3 was obtained.
N-Ethyl-2-phenyl-N'-tosylacetimidamide (1a). Yield 25%. Yellow oil. 1H NMR (200 MHz) 0.99 (t, J 7.3Hz, 3H, CH3), 2.39 (s, 3H, CH3Ph), 3.20-3.33 (m, 2H, CH2), 4.32 (s, 2H, CH2Ph), 5.25 (s, 1H, NH), 7.09-7.87 (m, 9H, ArH) ppm. 13C NMR (50 MHz) 13.7 (CH3), 21.6 (CH3), 37.2 (CH2), 39.9 (CH2), 126.5 (CH), 128.3 (CH), 129.4 (CH), 129.6 (CH), 130.3 (CH), 133.4 (C), 141.1 (C), 142.3 (C), 166.7 (C) ppm. ESI-MS: m/z 339 [M+Na]. C17H20N2O2S (316.36): calcd. C 64.54, H 6.36, N 8.85% found C 64.32, H 6.54, N 8.69%
N-Ethyl-N'tosyl-formimidamide (2a). Yield 20%. Mp 100-101°C (white crystals from CH2Cl2 and i-Pr2O). 1H NMR (200 MHz) 1.15-1.25 (m, 3H, CH3), 2.40 (s, 3H, CH3Ph), 3.29-3.43 (m, 2H, CH2), 6.80 (sb, 1H, NH), 7.28 e 7.56 (2d, 2+2H, 4ArH), 8.21 (d, J=4.80Hz, 1H, CH) ppm. 13C NMR (50 MHz) 13.9 (CH3), 21.6 (CH3), 36.9 (CH2), 126.6 (CH), 129.8 (CH), 139.6 (C),
