Trialkanolamine catalyst

The incorporation of homogenous Ti(lV)/trialkanolamine catalyst in polymeric membranes has been investigated as heterogeneous catalysts for the selective oxidation of secondary amines to nitrones by alkyl hydroperoxides (Buonomeima et al., 2004, 2006). Three polymers, PVDF, a modified polyetherketone (PEEK-WC), and polyacrUo-nitrile (PAN) with different functional groups and chemical-physical properties were used to tune the reactivity of the catalytic polymeric membranes. 

The physical properties of commercial alkoxysilanes are provided in Table 1. Two classes of silane esters have very distinct properties and are generally considered apart from alkoxysilanes. Sdatranes are compounds derived from trialkanolamines and have siHcon—nitrogen coordination. These are generally hydrolytically stable and have unique physiological properties (3). A second special class of monomeric esters are cycHc diesters of polyethyleneoxide glycols designated sila-crowns, which have appHcation as catalysts (4). Neither silatranes nor sila-crowns are considered herein. 

However, in some cases the use of a basic catalyst can result in cleavage of the Si—C bond59,76. For example, treatment of dichloromethyltriethoxysilane with trialkanolamine in the presence of sodium methoxide affords the corresponding 1-ethoxysilatrane in 84% yield (equation 22). The target l-dichloromethyl-4-ethylsilatrane (96%) is formed in the absence of a catalyst59. 

Along with the development of chiral Lewis acid catalysts, a chiral trialkanolamine (42) has been used to prepare the catalyst (43) (Eq. 19). By use of this zirconium complex as a catalyst, enantioselective addition of the azide to meso epoxides was achieved [20a]. Thus, the oxirane ring was opened by /-PrMe2SiN3 to give the adduct (44) with high enantioselectivity (Eq. 20). In another example, a diamide ligand (45), which behaves as a tetradentate ligand, was used to achieve a similar reaction (Eqs 21 and 22) [20b]. 

More recently (1994), discrete early transition metal (Ti, V, Nb, orTa) al-koxide complexes containing homochiral trialkanolamine ligands (392) were prepared and their usefulness as highly enantioselective catalysts was demonstrated. It is noteworthy that earlier work on the reactions of tetradentate triethanolamine with transition metal alkoxides was reported to yield insoluble products (6). 

Nugent adapted the zirconium trialkanolamine complex developed for the enantioselective addition of TMSN3 (Scheme 1) to catalyze the addition of bromide, where substitution of bromide for azide at the metal center was proposed to account for the epoxide halogenation product (Scheme 15) [29]. When a large excess of the bromide source was used to suppress azido alcohol formation, a wide range of cyclic epoxides reacted with 5 mol % of the catalyst to afford good yields of the bromohydrins in 84-96% ee. 

The point of the sudden change in the PO consumption rate is the moment of total transformation of the initial amine in a trialkanolamine of lower catalytic activity. Because of the low PO polymerisation rate in the second part of the reaction, at normal polymerisation temperatures of 110-120 °C, it is practically impossible to obtain, in the presence of tertiary amines as catalysts, polyether polyols with an hydroxyl number lower than 400 mg KOH/g. 

Bonchio, M., Licini, G Modena, G., Moro, S Bortolini, O., Traldi, P., and Nugent W.A. (1999) Enantioselective Ti(IV) sulfoxidation catalysts bearing C3-symmetric trialkanolamine ligands solution speciation by H NMR and ESI-MS analysis. /. Am. Chem. Soc.,... 

The sulfoxidation of organosulfur compounds by tert-butyl hydroperoxide has been effected catalytically using titanium alkoxide-based catalyst. A robust titanium alkoxide catalyst was developed from the reaction of a homochiral trialkanolamine N CH2CHR(0H) 3 (R = H, MePh) with Ti(OPr )4 to form a mononuclear isopropoxy titanatrane (E 0)Ti 0CHRCH2 3N containing five-coordinated titanium. 

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