Efficient bismuth catalysts for transcarbamoylation

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

“…182 Finally, an interesting study showed that oxime-blocked isocyanates induce cross-linking by generating amines and hydrazines under UV radiation. 183 (69,Scheme 45), bearing two functions: a labile hydrogen and a methacrylate double bond, which can homopolymerize leading to polyurethane and polyacrylate interpenetrated networks. In the same way, polyurethane−urea/polyvinyl simultaneous interpenetrating polymer networks were prepared starting from a mixture of isocyanate prepolymer blocked with N-(11′-dimethyl-3-oxobutyl) acrylamide oxime, chain extender, vinyl monomers, and catalysts.…”

Recent Advances in Bismuth-Catalyzed Organic Synthesis

“…Bi(OTf) 3 was reported to be a very efficient catalyst in the transcarbamoylation reaction of N-alkyl O-alkyl carbamates. For example, in the presence of Bi(OTf) 3 (1.0 mol%), the reaction of N-hexyl O-methyl carbamate with equivalent amount of n-octanol at 160 o C for 2 h afforded N-hexyl O-octyl carbamate in 92% GC yield (Scheme 50) [67]. Bi(OTf) 3 shows higher catalytic activity than BiCl 3 and other Lewis acid catalysts such as Bu 2 Sn(OAc) 2 , Sc(OTf) 3 , Sm(OTf) 3 , Yb(OTf) 3 , La(OTf) 3 .…”

Iron‐Catalyzed Reaction of Urea with Alcohols and Amines: A Safe Alternative for the Synthesis of Primary Carbamates

“…On the other hand, the iron-catalyzed transcarbamoylationr eactionu sing different substitutedc arbamates (6a-c)w orks well. [19] As shown in Ta ble 2( entries 5-7), this latter transformation provided the primary carbamate 3a in excellent yields using either O-methyl, -benzyl, and -phenyl carbamates. In this case acompetitive substitution reaction between the starting alcohola nd the leaving group can take place,b ut 1-undecenol was shown to be more reactive in all examples.…”