Mild and High‐Yielding Molybdenum(VI) Dichloride Dioxide‐Catalyzed Formation of Mono‐, Di‐, Tri‐, and Tetracarbamates from Alcohols and Aromatic or Aliphatic Isocyanates

Abstract

Both molybdenum(V) dichloride dioxide (MoO 2 Cl 2 ) and its dimethylformamide (DMF) complex catalyze the addition of alcohols to isocyanates giving carbamates. Most additions proceed to completion at room temperature within 20 min using as little as 0.1 mol% of the catalyst when working on a 1-mmol scale or just 100 ppm working on a 20-mmol scale. Sterically encumbered substrates reacted to completion when 1 mol% of the catalyst was employed. Diols, triols, and tetraols reacted with monoisocyanates likewise, as did monofunctional alcohols and diisocyanates. These pairings furnished di-, tri-, tetra-, and dicarbamates, respectively. Reactants, which were poorly soluble in CH 2 Cl 2 at room temperature required elevating the temperature and possibly choosing a higher-boiling solvent (ClCH 2 CH 2 Cl, DMF) as well. Additions of diols to diisocyanates were feasible, too, giving polycarbamates as we presume.

One-Pot Conversion of Epoxidized Soybean Oil (ESO) into Soy-Based Polyurethanes by MoCl2O2 Catalysis

“…For this reason, molybdenum-based compounds have found several applications as clean alternatives to heavy metals in the petroleum and plastic industries. In particular, MoCl 2 O 2 , and its related complexes, serve well as Lewis acid catalysts for several organic transformations [ 29 ], ranging from oxidation to acylation, reduction, and carbamylation [ 30 , 31 , 32 ]…”

“…Brückner and coworkers have recently studied catalytic activity of MoCl 2 O 2 and related complexes in the formation of mono-, di-, tri-, and tetracarbamates from a variety of alcohols and isocyanates [ 30 ]. They found that these reactions proceed to completion at room temperature in few minutes using as little as 0.1–1 mol % of the catalyst in chlorinated solvents.…”

A Simple and Effective Synthesis of 3- and 4-((Phenylcarbamoyl)oxy)benzoic Acids

“…reacting phenols with the general formula 2 with various phenyl isocyanates (3) in the presence of a catalytic amount of 4-dimethylamino pyridine (4-DMAP) in CH 2 Cl 2 or DMF (Scheme 2A). 18,19 However, this reaction did not produce the desired carbamates as no reaction was observed. Therefore, we had to plan an alternative synthetic route.…”

Formation of Hindered Arylcarbamates using Alkyl Aryl Carbonates under Highly Reactive Conditions

“…14 In cases in which isocyanates are involved, in addition to an additional step to prepare the isocyanates, a catalyst and long reaction time are usually needed for the formation of hindered carbamates. 15 The other method is to use dialkyl dicarbonates. Even the most hindered O -tertiary carbamate can be readily prepared using the method.…”