Titanium-tetra isopropoxide

Colloidal TiOj is made by hydrolysing titanium tetrachloride or titanium tetra-isopropoxide. In the author s laboratory a procedure has been developed which allows one to obtain the colloid as a powder from titanium tetraisopropoxide, after careful evaporation of the solvent The powder can be redissolved to give a transparent... 

The asymmetric dihydroxylation protocol was the second massive contribution by Professor Barry Sharpless to synthetic organic chemistry. The first procedure, introduced with Katsuki, involves the catalytic asymmetric epoxida-tion of allylic alcohols. A typical example is shown in Scheme 17, wherein ( )-allylic alcohol (23) is epoxidized with tert-b utyl hyd roperox ide, in the presence of titanium tetra-isopropoxide and optically active diethyl tartrate to give the... 

An important breakthrough in asymmetric epoxidation has been the Katsuki-Sharpless invention [1], The reaction uses a chiral Ti(IV) catalyst, t-butylhydroperoxide as the oxidant and it works only for allylic alcohols as the substrate. In the first report titanium is applied in a stoichiometric amount. The chirality is introduced in the catalyst by reacting titanium tetra-isopropoxide... 

Jeong and co-workers utilized a cobalt-alkyne complex to enhance enantioselectivity of the addition of bis (homoallyl)zinc to propargyl aldehydes 68 by the exaggeration of steric environment. The reaction provided optically enriched propargyl alcohol 69 in the presence of a chiral ligand and titanium tetra(isopropoxide) in excess. Adduct 69 was subjected to PKR to yield optically enriched bicyclic compounds 70 (Equation (39)). ... 

Preparation of Thin Tilms of TiOx on Palladium Foils. Following the procedure reported by Takahashi, an isopropanol based sol of titanium tetra-isopropoxide (TnP) was prepared (10 mL of TUP in 48.4 mL of 2-propanol), to which 6.7 mL of diethanolamine was added to inhibit the formation of oxides. This mixture was stirred for two hours, at which time gel formation was initiated by the addition of 28.1 mL of a dilute water solution (1.42 mL water in 30 mL of 2-propanol). The resulting molar ratio of water to TUP was 2 1, as was recommended by Takahashi and co-workers (22). The palladium substrates were dipped vertically into this solution and then clamped on edge while draining to allow the excess to drip off and to prepare as even a coating as possible. The membranes were then air-dried in a vertical position at 100°C for one hour, followed by a post-treatment with hydrogen (see Figure 2). 

Titania gels produced in this study were formed by the acid hydrolysis of titanium tetra-isopropoxide [14]. Although all the sols were produced in a similar manner, the final pH for the formation was controlled by the addition of ammonium hydroxide. The acid hydrolysis of titanium tetra-isopropoxide may be considered as follows ... 

Transesterification of dimethyl carbonate by phenol, catalysed with dioctyl tin oxide and titanium tetra-isopropoxide, has been effected by passage of the mixture through 5A molecular sieve at 175-185°C under pressure (203 Bar). Unreacted starting materials were removed separately by heating at 185-195X for 2 hours to give diphenyl carbonate in 85% yield (ref. 15). 

Tridentate BINOL catalysts can be derived from titanium tetra(isopropoxide), BINOL ligands, and hindered amine bases. These catalysts have also been shown to provide good yields and ee s for the aldol reactions at low temperatures of 2-methoxypropene with several aldehydes to the P-hydroxyketones, but an acid workup of the products is required. 

N-doped Ti02 was prepared by a wet method, i.e., the hydrolysis of titanium tetra-isopropoxide (TTIP) or titanium tetrachloride with an aqueous ammonia solution, followed by calcination at temperatures above 330°C [403]. The maximum absorption of visible light by this N-doped 77O2 was about 50% at around 440 nm. To evaluate the... 

Black sand Titanium tetra-isopropoxide (1.5 mL) is dissolved in isopropanol (40.0 mL). Pre-dried Si/Black sand particles (0.2 g) are dispersed in the solution and sonicated for 0.5 h. Then, it is stirred for 5. The mixture is heated at 80°C for 3 h and then calcined at 450°C for 3 h Removal of six dyes Direct red 80, Eosin B, Rose bengal. Orange II, Ethyl violet, Rhodamine B [512]... 

Of particular value in complex syntheses is a technique for epoxidation that can be applied to allylic alcohols and that directs the approach of the oxidizing group to one or the other of the two faces of the double bond. This results in the formation of one enantiomeric form in excess of the other and, thus, stands as an asymmetric synthesis. The technique is simple and consists of the formation of a chiral catalyst, a coordination complex, from titanium tetra-isopropoxide and one of the optically active forms of a dialkyl tartrate. The allylic alcohol associates with this complex in a specific way and then is epoxidized on one face by t-butyl hydroperoxide. The epoxide is produced in high enantiomeric excess, frequently more than 95%. This process has been used widely in organic synthesis since its discovery in 1980. It is now known as the Sharpless epoxidation. 

The stereoisomers of ethyl menthyl (methylthio)methylphosphonate 32 were obtained from commercially available diethyl (methylthio)methylphosphonate by subjecting them to a highly diastereoselective hydroperoxide oxidation in the presence of catalytic amounts of a titanium (/ )- or (5)-BlNOL complex. The prevailing phosphorus stereoisomer was oxidized with cumene hydroperoxide in the presence of a Sharpless complex between titanium tetra(isopropoxide) and diethyl (/ ,/ )- or (S,S)-tartrate, to yield the corresponding (methylsulfinyl) methylphosphonates 33 (76-82% de). The sulfoxide 33 was obtained in a diastereo-merically pure form (>98% de, upon recrystallisation) and was shown to have an (/ P,Ss)-configuration (Scheme 11) [32]. 

In 2007, Feng et al. reported an efficient self-assembled catalytic system for the addition of trimethylsilyl cyanide to imines. The combined use of cinchonine (27), achiral 3,3 -(2-naphthyl)-2,2 -biphenol (28), and titanium tetra-isopropoxide gave an efficient catalyst for aldimines and ketimines (Scheme 7.19). Cinchonine induces a chiral environment around the titanium atom by fixing a stable chiral configuration to the biphenol ligand, and also activates hydrogen cyanide, generated in situ. In addition to trimethylsilyl cyanide, safer ethyl cyanoformate can be used with similar results. 

The reaction is normally performed at low temperatures (-30 to 0°) in methylene chloride, and is catalytic in the chiral component diethyl or diisopropyl tartrate (DET or DIPT), and in titanium tetra-isopropoxide, provided water is rigorously excluded 4 A molecular sieves may be added to ensure this. Both enantiomers of tartaric acid are commercially available, allowing the synthesis of either enantiomer of the epoxylalcohol. The key to the remarkable enzyme-like enantioselectivity lies in the complex formed from the... 

TIP (titanium-tetra-isopropoxide), 9, 11. See also ZIP titanate glasses melt-quenched, 11 RDF, 11... 

Precursor Solutions The reagents used were titanium tetra-isopropoxide (TTIP Sigma-Aldrich, 97 wt%), propanol (Ajax Finechem, 99.7 wt%), and nitric acid (Univar, 70 wt%). 

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