Carbamates, continuous-flow

For example, the anodic oxidation of a silyl-substituted carbamate to generate a solution of N-acyliminium ion and the cathodic reduction of cinnamyl chloride in the presence of chlorotrimethylsilane to generate the corresponding allylsilane can be carried out simultaneously in a single electrochemical microflow cell under continuous flow conditions (Figure 5.10). The N-acyliminium ion, the anodic product, is allowed to react with the allylsilane, the cathodic product, to give the coupling product. 

OS 30] [R 30] [P 22] By simple flow switching, serial combinatorial synthesis for creating a cation pool from diverse carbamates and silyl enol ethers was accomplished (Figure 4.46) [66, 67]. The conversions and selectivities were comparable to continuous processing using three feed streams only (see Conversion/yield/selec-tivity, above). 

Selective precipitation of ammonium carbamate can be achieved by reacting gaseous C02 and NH3 in anhydrous ethanol, 1-propanol or DMF in a flow reactor that operates in continuous mode [20]. And then, the pure ammonium carbamate is used to produce urea with good yield (up to 54 % on carbamate basis) at 120-140 °C in the presence of inexpensive Cu (II) and Zn (II) catalysts. (Scheme 6.3)... 

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