Mannich with isocyanates

The N-sulfinyl (thio)ureas are modular and easily accessible in one step by condensing tert-butanesulfinamide with the appropriate isocyanate or isothiocyanate. Figure 6.64 shows a representative selection of the prepared N-sulfinyl (thio)ureas evaluated for their catalytic activity in the aza-Henry (nitro-Mannich) reaction of N-Boc-protected benzaldimine and nitroethane producing adduct 1. 

Its synthesis is based on the cyclisation of the keto Mannich base salt 9 with hydrazine hydrate to yield 3-(4-chlorophenyl)-2-pyrazoline (10), which is then carbamoylated with 4-chlorophenyl-isocyanate, as shown is Scheme 1.16. 

A practical and effective crossHnking mechanism in cathodic electrocoating is done with polyfunctional blocked isocyanates. The mechanism involves the reaction of an isocyanate group (NCO) with the hydroxy group of the epoxy backbone and liberation of the blocking group. Other crossHnking mechanisms that have been studied are use of addition polymers, Mannich bases, Michael adducts [110] sulfonium stabilized polymers, transesterification reaction of hydroxy, alkoxy, amido and ester systems with hydroxy functional cathodic backbone (Fig. 7-5) [111-114]. 

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