Efficient Inhibition of Re-blocking During the Deblocking of Blocked Isocyanates

摘要

3-Silylpropanols bearing allyl or aryl groups on the silicon atom were found to act as isocyanate blocking agents that can allow to deblock with efficient inhibition of re-blocking. As a result of the inhibition, the isocyanates blocked by 3-silylpropanols showed an exceptional lower deblocking temperature than by a conventional aliphatic alcohol. The inhibition is based upon the decomposition reaction of 3-silylpropanols to a 5-membered cyclic silane and propylene or arene, where beta-silyl cation intermediates may play a key role. The new blocked isocyanates can tolerate water, whereas previously well-known low-temperature-deblockable agents, such as methylethyl ketone oxime (MEKO), are not generally compatible with water.