Selective derivatization of oxime-blocked tolylene-2,4-diisocyanate

A selective reaction of cyclohexanone oxime-blocked tolylene-2,4-diisocyanate (2,4-TDI) with amino siloxane was observed, in which amines were capable of discriminating two reactive groups in the 2,4-TDI molecule. Thus, tolylene-2-tert-butyldimethylsilyloxyethyl carbamide-4-cyclohexanone oxime carbamate was synthesized and its precise structure was determined by single-crystal X-ray diffraction. Moreover, it was found that oxime-blocked isocyanate could react selectively with the NH2 group with the OH group unprotected in ethanolamine.

Tolylene-2,4-diisocyanate is first blocked by reacting with cyclohexanone oxime (a). The selective reaction of oxime-blocked isocyanate group is observed when treated with protected ethanolamine derivatives (b). The oxime-blocked isocyanate can react preferentially with the NH2 group over the OH group in ethanolamine (c).Figure optionsDownload as PowerPoint slide