A ‘waterproof’ catalyst for the oxidation of secondary amines to nitrones with alkyl hydroperoxides

Effective Oxidation of Secondary Amines to Nitrones with Alkyl Hydroperoxides Catalysed by (Trialkanolaminato)titanium(IV) Complexes

“…[21,22] In the presence of catalyst 2c (1.0 %), for example, amine oxidations can be carried out in chloroform at 60°C in nearly quantitative yields in as little as 1 hour.…”

Oxidation of secondary amines by molecular oxygen and cyclohexanone monooxygenase

“…This methodology uses hydrogen peroxide as primary oxidant in the presence of catalysts such as Na 2 MoO 4 or Na 2 WO 4 , 15 MeReO 3 16 or SeO 2 . 17 Very recently, alkyl hydroperoxides have been used as primary oxidant and titanium alkoxide complexes as catalyst, 18 and protected from the water formed as a co-product by the combined use of trialkanolamine ligands and molecular sieves. 18…”

C3‐Symmetric Titanium(IV) Triphenolate Amino Complexes for a Fast and Effective Oxidation of Secondary Amines to Nitrones with Hydrogen Peroxide

“…In the case of substrate 3e (Table 3, entry 5) a single nitrone was obtained, consistent with the regioselectivity already observed with other oxidizing systems. [8,9] In summary, we have reported that the C 3 -symmetrical Ti(IV) complex 2 is an effective catalyst for the oxidation of secondary amines to nitrones. Thanks to the high stability of the complex 2, the inexpensive and green aqueous hydrogen peroxide can be used as primary oxidant, with catalyst loadings down to 0.01%, high selectivity for the nitrone production, reaching TONs up to 8000 and fast reactions (TOFs up to 11,000).…”

“…[7] In principle, the oxidative approach, using hydrogen peroxide (or urea hydrogen peroxide) or alkyl hydroperoxide starting from corresponding secondary amines, provides the most direct and general method for preparing nitrones. [8,9] Hydrogen peroxide (2-7 equiv.) is used as primary oxidant in the presence of a catalyst (1-8% mol) such as Na 2 MoO 4 , Na 2 WO 4 , CH 3 ReO 3 or SeO 2 .…”

“…[9] Nitrones are obtained in high yield (up to 98%) under homogeneous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity can be achieved with as little as 1% catalyst.…”