RESUMEN
An economical and versatile protocol for the one-pot synthesis of monomethylamines by reduction of N-substituted carbonylimidazoles with NaBH4/I2 in THF at reflux temperature is described. This method used no special catalyst and various monomethylamines can be easily obtained in moderate to good yields from a wide range of raw materials including amines (primary amines and secondary amines), carboxylic acids and isocyanates. Besides, an interesting reduction selectivity was observed. Exploration of the reaction process shows that it undergoes a two-step pathway via a formamide intermediate and the reduction of the formamide intermediate to monomethylamine as the rate-determining step. This work can contribute significantly expanding the applications of N-substituted carbonylimidazoles.
RESUMEN
We develop a simple formula for estimating the effect of Four- Wave Mixing (FWM) on received signal quality in coherent optical systems using Orthogonal Frequency Division Multiplexing (OFDM) for dispersion compensation. This shows the nonlinear limit is substantially independent of the number of OFDM subcarriers. Our analysis agrees well with full split-step Fourier method simulations, so allows the nonlinear limit of multi-span systems to be estimated without lengthy simulations.