Titanium titanocene dichloride

Titanium white pigments, commercial production of, 19 388 Titanium white rutile pigment, 19 391 Titanium zinc oxide, 5 603 Titanium-zirconium-molybdenum (TZM) alloy, 17 14-15 Titanocene, 25 118 Titanocene catalysts, 16 19 Titanocene dichloride, 25 105 Titanocene synthons, 25 116 Titanocycles, 25 116... 

The Diels-Alder reaction outlined above is a typical example of the utilization of axially chiral allenes, accessible through 1,6-addition or other methods, to generate selectively new stereogenic centers. This transfer of chirality is also possible via in-termolecular Diels-Alder reactions of vinylallenes [57], aldol reactions of allenyl eno-lates [19f] and Ireland-Claisen rearrangements of silyl allenylketene acetals [58]. Furthermore, it has been utilized recently in the diastereoselective oxidation of titanium allenyl enolates (formed by deprotonation of /3-allenecarboxylates of type 65 and transmetalation with titanocene dichloride) with dimethyl dioxirane (DMDO) [25, 59] and in subsequent acid- or gold-catalyzed cycloisomerization reactions of a-hydroxyallenes into 2,5-dihydrofurans (cf. Chapter 15) [25, 59, 60],... 

An alternative, but related, route to allenic titanium reagents from propargylic esters has been reported recently. Reaction of titanocene dichloride with BuMgCl and Mg yields a reactive titanocene intermediate, formulated as Cp2Ti. This reduced Ti species reacts in situ by oxidative addition to propargylic acetates. The allenyltitanium reagents thus produced add to aldehydes and ketones, as expected, to afford homopropargylic alcohols (Table 9.27) [43]. 

Scheme 12.4 Grafting of titanocene dichloride onto siliceous supports and subsequent formation of active titanium centers.

Titanocene dichloride ALDRICH Bis(cyclopentadienyl)titanium dichloride Titanium, dichloro-n-cyclopentadienyl- (8) Titanium, dichlorobis(r -2,4-cyclopentadienyl-1-yl)- (9) (1271-19-8)... 

Titanium(IV) isopropoxide, 92-95, 99 Titanocene dichloride, 163, 164 p-Toluenesulfinyl chloride, 8 p-Toluenesulfinylimidazolide, 535 p-Toluencsulfonic acid, 535 p-Toluenesulfonyl azide, 535-536 p-Toluenesulfonyl chloride, 536 p-Toluenesulfonyl cyanide, 536 /7-Toluenesulfonylhydrazine, 537... 

The cyclisation of alkenes by low valent titanium has also been applied to intramolecular processes. Thus the reduction of titanocenes bearing pendant alkenyl substituents [TiCl2(r -C5Me4XCH = CHR)2] (X = SiMe2, CH2, CHMe R = H, Me) provides chiral titanacyclopentanes shown in Scheme 2.16 The titan-acyclopentanes could then be cleaved with HC1 to provide new titanocene dichlorides in which the two cyclopentadienyl ligands were linked by a hydrocarbon chain. 

After formation of complex by combination of the titanocene dichloride and trialkyl aluminum, alkylation of the titanium component is presumed to take place. 

Kopf-Maier P (1990) Intracellular localization of titanium within xenografted sensitive human tumors after treatment with the antitumor agent titanocene dichloride. J Struct Biol 105 35 45... 

Guo M, Guo Z, Sadler PJ (2001) Titanium(IV) targets phosphoesters on nucleotides implications for the mechanism of action of the anticancer drug titanocene dichloride. J Biol Inorg Chem 6 698-707... 

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