Cyclohexanone oxime is the key intermediate of e-caprolactam synthesis. A new environmental friendly process, the selective hydrogenation of 1-nitro-cyclohexene, was optimized in a high pressure continuous flow reactor (H-Cube®) using different catalysts. The order of selectivity for obtaining cyclohexanone oxime was Pd < Rh < RuO2 < PtO2 < Ir < Au, that correlates perfectly with the width of the d-orbital of these metals. The best result yielding of cyclohexanone oxime (98%) was obtained on 1%Au/TiO2 at 70°C, 0.25 ml/min, and 70 bar H2 in ethanol. A 48-fold scale up was successfully achieved using H-Cube Midi™ (overall productivity: 150g/day). The reaction mechanism on gold catalyst was studied by hydrogenation of analogous compounds, intermediate trapping and deuteration. Deuteration of 1-nitro-cyclohexene resulted in pure syn-stereoisomer of cyclohexanone oxime, as proved by NMR. One step 1,4-hydrogenation was proposed as reaction mechanism on Au/TiO2. Furthermore, the method developed offers a new procedure for synthesis of syn-oximes, in general.