Synthesis of 1,3-dialkyldiazetidinediones from N,N'-dialkylaminocarbonylcarbamic chlorides (2,4-dialkylallophanoyl chlorides)

Isocyanate-crosslinked silica aerogel monoliths: preparation and characterization

“…As expected, the isocyanate stretch at $2270 cm À1 is absent in the composites indicating that the isocyanate groups have completely reacted. The carbonyl stretch assigned to the diazetidinedione group of N3200 at 1767 cm À1 survives the crosslinking conditions [16]. As expected, the isocyanurate ring carbonyl stretch at $1690 cm À1 is present in both N3200 and N3300A [17].…”

“…For such applications the vapor pressure of the isocyanate itself must be kept low. Such higher viscosity/lower vapor pressure isocyanates can be made either by catalytic condensation of lower molecular weight diisocyanates [19], for example with hexamethylene diisocyanate (HDI), or by direct synthesis, as for example via the base-catalyzed ring closure of the condensation product of a N,N 0 -dialkylurea and phosgene [16]. Because the isocyanurate system is thermodynamically more stable than diazetidinedione [19], it is easier to prepare it selectively.…”

N-Heterocyclic Carbenes as Highly Efficient Catalysts for the Cyclotrimerization of Isocyanates

“…When SIPr (1 mol %) was added to a solution 1,6-diisocyanatohexane (0.5 M, THF) at room temperature, a translucent solid formed within minutes. Further characterization of this solid revealed that a polyamide was formed with an exclusive isocyanurate-linked backbone (as determined by FT-IR spectroscopy 24,25 ).…”

Isocyanates, Organic

“…Aliphatic isocyanate dimers can, however, be synthesized via the phosgenation of N,N -disubstituted ureas to yield N-(chlorocarbonyl)chloroformamidine intermediates which are subsequently converted by partial hydrolysis and base catalyzed cyclization. This is also the method of choice for the synthesis of 1-alkyl-3-aryl-1,3-diazetidiones (mixed dimers of aromatic and aliphatic isocyanates) (58).…”