Going beyond the barriers of aza-Michael reactions: controlling the selectivity of acrylates towards primary amino-PDMS

The aza-Michael reaction of aliphatic primary amines with electron-deficient double bonds proceeds through two additions possibly leading to a mixture of amines with different degrees of substitution. We present here model reactions involving acrylates as Michael acceptors and amino-PDMS as Michael donors, and the impact of experimental conditions (temperature, organo-catalyst, and solvent) on the selectivity of such a reaction. While hydrocarbon alcohols favor monoaddition, halogenated alcohols favor double substitution. Tuning the operating conditions allowed the formation of either a monoadduct or a diadduct with no primary amine left, demonstrating that the structure of PDMS can be modified in a controlled manner without using any metal catalyst.