Organic reaction in water. Part 1. A convenient method for reduction of imines using zinc powder

Reductive amination with zinc powder in aqueous media

“…We were interested in the use of zinc metal in view of several factors promoting its use as a green reductant: i) atom economy, ii) low toxicity, iii) relative stability in air and water, and iv) low cost. Examples of the reduction of imines by zinc metal are reported, either in organic solvents [ 25 – 29 ] or in basic aqueous medium [ 30 ]. We recognized that this process could be considerably simplified by the development of a one-pot procedure involving the combination of a primary amine, aldehyde, and zinc in water, thereby avoiding the isolation of the intermediate imine.…”

Mischmetall and Zn–Cu Couple as Efficient Reagents for the Pinacol Coupling of Aldimines

“…Zinc is another potential coupling-mediator. However, due to variable quality of zinc dust the reproducibility is questionable, 13,14 thus requiring certain modifications to be introduced. For example, Zn-Cu couple, prepared in situ, 15,16 was reported to induce imine coupling in nonprotic solvents.…”

Pd‐Catalyzed Csp2H Functionalization of Heteroarenes via Isocyanide Insertion: Concise Synthesis of Di‐(Hetero)Aryl Ketones and Di‐(Hetero)Aryl Alkylamines

“…Compared with the reduction of CO and CC bonds, the reduction of CN bonds remains a big challenge due to its weak reactivity 11b. After several attempts, we were able to achieve complete conversion of imine 3 aa using two equivalents of zinc dust in alkaline solution11c at 60 °C for 2 h under ultrasonication, providing 6 aa in 62 % yield. The results summarized in Table 4 show that imines derived from tert ‐butyl‐, cyclohexyl‐ and 1,1,3,3‐tetramethylbutyl isocyanide gave the corresponding secondary amines in moderate to good yields ( 6 aa – 6 al ).…”