Lithium Dibenzylamide, a Simple, Selective and Highly Efficient Catalyst for Isocyanate Cyclotrimerization to Isocyanurate

Abstract

Lithium dibenzylamide catalyzed the rapid and essentially quantitative cyclotrimerization of a variety of isocyanates under mild conditions and could be recycled for six times in high yield.

Key words

lithium amides - catalysis - isocyanates cyclotrimerization - isocyanurates

References and Notes

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30

Representative Procedure: An oven-dried Schlenk tube under nitrogen was charged with phenyl isocyanate, lithium dibenzylamide (0.1 mol%), and Et₂O (30 mL). The reaction mixture was stirred at r.t. for 2 min. The resulting precipitate was filtered off, washed with Et₂O (3 × 3 mL), and dried under reduced pressure to give the isocyanurate 1,3,5-triphenyl-1,3,5-triazinane-2,4,6-trione (1) as a white solid.

31

Procedure for Recycling Experiment of Lithium Dibenzylamide: Phenyl isocyanate was added to a solution of lithium dibenzylamide (0.1 mol%) in Et₂O (30 mL) with stirring. The reaction mixture was stirred at r.t. for the allotted time and filtered via a canula filter. The Et₂O filtrate was subjected to a second reaction cycle. This procedure was repeated six times (for details see Table  [³] ).