Question

Why are imines important?

Answer 1

Because imine formation represents `C-N` bond formation.........

Explanation:

From your organic chemistry course, you know that there relatively few ways to make `C-C` and `C-N` and `C-"heteroatom"` bonds in general. Of course, we may represent the formation of imines by the reaction:

`"Imine formation:"`

`R_1C(=O)R_2 + R_3NH_2 rarr R_1C(=NR_3)R_2 + H_2O`

These reactions are reasonably simple to accomplish by various (and straightforward) means. The fact that the reaction spits out water (i.e. it is a condensation reaction) provides a thermodynamic driving force to the reaction. And thus we have formed a carbon-heteroatom bond (of course, here, the bond is unsaturated). In the best circumstances we may reduce the imine function to give secondary amines.

`"Imine reduction:"`

`R_1C(=NR_3)R_2 + H^(-) rarr R_1C(H)(NR_3)R_2`

The hydride transfer reagent may by `LiAlH_4` or `KBEt_3H` or even `H_2` with transition metal catalysis.

Sometimes, this can be done with stereocontrol; of course we'd need a special hydride transfer agent, likely a chiral transition metal complex under dihydrogen.