Titanium Compounds isopropoxide

Reactions of lithium and titanium compounds 2, generated in situ by deprotonation of alkynylsilanes with tm-butyllithium, followed by addition of titanium(IV) isopropoxide and an aldehyde result either in a-hydroxyallenes without axial dissymmetry or in /J-hydroxyalkyn-es90 91. 

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)). ... 

A similar study was made on various titanium compounds. It was found that titanium dichloride diacetate and titanium dichloride di-isopropoxide produced high amounts of crystalline polyvinylisobutylether. On the other hand, the more acidic titanium tetrachloride produced more amorphous polymers. The insoluble titanium trichloride and titanium dichloride were ineffective as polymerization catalysts. The less acidic tetraisopropyltitanate and diethyltitanium dichloride were completely ineffective as catalysts. 

Butyl hypochlorite, 55 of phenols to quinones Benzoyl /-butyl nitroxide, 28 2,3-Dichloro-5,6-dicyano-l, 4-benzoqui-none, 104 Periodic acid, 238 of phosphorus compounds Dimethyldioxirane, 120 of selenium compounds Potassium permanganate, 258 of sulfides to sulfoxides and sulfones /-Butyl hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 51 ra-Chloroperbenzoic acid, 76, 112 Dimethyldioxirane, 120 of thiols to sulfur compounds Trimethylsilyl chlorochromate, 327... 

Titanium(IV) isopropoxide, 311 a,(3-Epoxy aldehydes and ketones Fluorine-Acetonitrile, 135 Oxodiperoxymolybdenum-(pyridine)(hexamethylphosphoric triamide), 227 a,(3-Epoxy silanes Allyltriisopropylsilane, 11 m-Chloroperbenzoic acid, 76 Esters (see also Dicarbonyl compounds, Unsaturated esters)... 

Titanium(IV) isopropoxide Chemical Abstracts nomenclature 2-propanol, titanium(4-f-) salt) is the titanium species of choice for preparation of the titanium tartrate complex in the asymmetric epoxidation process. The use of titanium(IV) t-butoxide has been recommended for those reactions in which the epoxy alcohol product is particularily sensitive to ring opening by the alkoxide. The 2-substituted epoxy alcohols (Section 3.2.5.2) are one such class of compounds. Ring opening by t-butoxide is much slower than by isopropoxide. With the reduced amount of catalyst that now is needed for all asymmetric epoxidations, the use of Ti(OBu )4 appears to be unnecessary in most cases, but the concept is worth noting. 

Preliminary results for asymmetric epoxidations of ( )-cinnamyl alcohol and geraniol using (15,25)-l,2-di(2-methoxyphenyl)ethane-l,2-diol or (15,25)-l,2-di(4-methoxyphenyl)ethane-l,2-diol as chiral auxiliaries with titanium(IV) isopropoxide and TBHP have been described. High enantioselectivity (95% ee) is observed when the 2-methoxyphenyl compound is used, while somewhat lower enantioselectivity (64% ee) and opposite face selectivity is described for the catalyst comprised of the 4-methoxyphenyl analog.Further elaboration of the scope and generality of these observations will be of interest. 

Many research groups have published results on catalyst activities and catalysis mechanisms. A wide variety of catalysts have been used in polycondensation of PBS, such as ScfCFjSOjj, ScCNTf jj, titanium tetrabutoxide, titanium(lV) isopropoxide phosphate acid, and titanium and tin composite. It is generally accepted that compounds of antimony, tin, and titanium are the most active catalysts for polycondensation. Among these catalysts, titanium tetrabutoxide (or tetrabutyl titanate) and titanium(IV) isopropoxide are usually used (Takiyama et al. 1994a, b Mochizuki et al. 1997) Yang et al. 2003. 

One of the characteristics of the infusion technique is that the materials entrapped in the surface may slowly diffuse out of the infused layer if they are volatile or highly mobile. One way to change permanently the surface is to employ polymeric infusant materials that may become chain entangled with the host polymer or to use soluble infusant compounds that can be chemically transformed into an insoluble material that is unable to diffuse into the surrounding solution. We have explored both of these methods by examining the infusion of poly(vinylpyrrolidone) (PVP) and titanium (IV) isopropoxide (which readily converts into... 

This method has proven to be an extremely useful means of synthesizing enantiomeri-cally enriched compounds. Various improvements in the methods for carrying out the Sharpless oxidation have been developed.56 The reaction can be done with catalytic amounts of titanium isopropoxide and the tartrate ligand.57 This procedure uses molecular sieves to sequester water, which has a deleterious effect on both the rate and enantioselectivity of the reaction. 

This procedure works well for most hydrophobic epoxy alcohols. The key advantage is that it is possible to remove tartrate, titanium isopropoxide and tert-butyl hydroperoxide, as those different compounds are not easily separated through distillation or recrystallization. 

Furukawa et al. [274] and Natta cl al. [275,276] succeeded independently in the preparation of crystalline polyacetaldehyde by using some organometallic compounds, such as diethylzinc or triethylaluminium, for the low-temperature polymerisation of acetaldehyde. Metal alkyls and metal alkoxides, e.g. aluminium isopropoxide, zinc ethoxide or ethyl orthotitanate, have also polymerised other aldehydes such as propionaldehyde and trichloroacetaldehyde to give crystalline polymers (Table 9.3) [270,275,277], A highly crystalline isotactic polymer has been obtained from the polymerisation of w-butyraldehyde with triethylaluminium or titanium tetrachloride-triethylaluminium (1 3) catalysts. Combinations of metal alkyl, e.g. diethylzinc, with water [278] or amine [279] appeared to give very efficient catalysts for aldehyde polymerisations. 

Breitenbucher and Hui (104) have recently reported the SP synthesis of a medium-large discrete library L3 of 8448 benzopyrans using the reductive amination cocktail formed from titanium isopropoxide and sodium triacetoxyborohydride, known in solution but whose applications to SP were rare and limited to single experiments (105, 106). The benzopyran scaffold is present in a number of biologically active compounds (107-110), and this library was tested in several biological assays (111). 

The metal salts of alcohols are called alkoxides, M(OR), where M is a metal and R is an alkyl group. Typical examples in the synthesis of ferroelectric thin films include titanium isopropoxide [Ti(OPr )4 where Pr represents isopropyl], tantalum ethoxide [Ta(OEt)5 where Et represents ethyl], and zirconium butoxide butanol [Zr(OBu )4 n-BuOH where Bu represents -butyl], an alkoxide/alcohol compound. The structure of this compound, shown in Figure 27.3a, illustrates its dimeric nature, that is, the fact that each molecule contains two metal centers. 

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