Diamination, titanium

A reagent more reactive than tris(dimethylamino)arsine employed by Weingarten and White 39) was tetrakis(dimethylamino)titanium (145). With this compound it was possible to prepare N,N-dimethyl(l-isopropyl-2-methylpropcnyl)amine (147) from diisopropyl ketone. Weingarten and White 39) have suggested a possible mechanism for this reaction (see p. 88). If benzaldehyde 39,111), formaldehyde 111), or acetaldehyde 39) is used, the corresponding gem diamine or aminal (143) is formed. 

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

Reductive coupling of imines 43 (R1 = Me, Ph or 2-pyridyl R2 = Me, Pr, t-Bu or PI1CH2) in THF under the influence of a low-valent titanium species, produced by the action of magnesium amalgam on titanium(IV) chloride, gave the DL-diamines... 

Although in the recent years the stereochemical control of aldol condensations has reached a level of efficiency which allows enantioselective syntheses of very complex compounds containing many asymmetric centres, the situation is still far from what one would consider "ideal". In the first place, the requirement of a substituent at the a-position of the enolate in order to achieve good stereoselection is a limitation which, however, can be overcome by using temporary bulky groups (such as alkylthio ethers, for instance). On the other hand, the ( )-enolates, which are necessary for the preparation of 2,3-anti aldols, are not so easily prepared as the (Z)-enolates and furthermore, they do not show selectivities as good as in the case of the (Z)-enolates. Finally, although elements other than boron -such as zirconium [30] and titanium [31]- have been also used succesfully much work remains to be done in the area of catalysis. In this context, the work of Mukaiyama and Kobayashi [32a,b,c] on asymmetric aldol reactions of silyl enol ethers with aldehydes promoted by tributyltin fluoride and a chiral diamine coordinated to tin(II) triflate... 

Pelizzetti et al. (1990) investigated the photocatalytic degradation of atrazine in solution in the presence of suspended titanium dioxide as a catalyst under simulated sunlight. Degradation was rapid but mineralization did not occur. Intermediate compounds included 6-hydroxy-A/-ethyl-/V -(l-methylethyl)-5 triazine-2,4-diamine, 2,4-diamino-6-chloro-A/-(l-methylethyl)-5-triazine, 2,4-di-amino-6-chloro-/V-ethyl-5-triazine, 2,4-diamino-6-chloro-5-triazine, 2,4-diamino-6-hydroxy-5-tri-azine, 2-amino-4,6-dihydroxy-5-triazine, 2-amino-4-hydroxy-6-chloro-5-triazine, 2,4-dihydroxy-6-chloro-s-triazine, 6-chloro-/V-acetyl-/V -(l-methylethyl)-5-triazine-2,4-diamine, and cyanuric acid as the final product. 

Gibson and coworkers have developed a series of tetradentate bis(iso-propoxide)-Ai,Ai-bis(6-methylenimino-2,4-di-tcrt-butylphenoxy)cyclohexyl-(lR,2R)-diamine-supported titanium(IV)-salen complexes 133-138 (Fig. 19). These complexes... 

New catalysts were also discovered by combinatorial methods for epoxidation, specifically, diamine Mn complexes, highly active Fe and salen complexes, and titanium-silsesquioxane.223... 

Fuel additives - [AMNES-CYCLOALIPHATIC AMINES] (Vol 2) - [SULFONIC ACIDS] (Vol 23) -arsenic compds as [ARSENIC COMPOUNDS] (Vol 3) -boron compds as [BORON COMPOUNDS - BORIC ACID ESTERS] (Vol 4) -coordination compounds as [COORDINATION COMPOUNDS] (Vol 7) -ethers m [ETHERS] (Vol 9) -magnesium alkyls as [MAGNESIUM COMPOUNDS] (Vol 15) -polyamines as [DIAMINES AND HIGHER AMINES ALIPHATIC] (Vol 8) -htanates as [TITANIUM COMPOUNDS - ORGANIC] (Vol 24) -use of copper compounds [COPPER COMPOUNDS] (Vol 7)... 

Butyllithium-Tetramethylethylene-diamine, 212 Hexamethylditin, 142 Titanium(IV) isopropoxide, 165 Tributyltin chloride, 158, 315... 

The sulfite anion radical (SOI) is obtained from sodium sulfite upon the action of titanium trichloride in water in the presence of ethylene diamine tetraacetic acid (as a complexing agent) and hydrogen peroxide (Bradic Wilkins 1984). Scheme 1-91 below shows this type of SOI generation. 

In other examples, compounds in which a metal atom is already coordinated in a molecule can be used as a comonomer in an addition polymerization. Two examples involve the ferrocenes discussed in Chapter 6. The vinyl ferrocene molecule is shown in 7.14, and a similar vinyl manganese complex in 7.15.30 An alternative approach involves condensation polymerization. For example, if the R group in the ferrocene unit shown in 7.16 contains a hydroxyl group, it can be copolymerized with a diacid chloride. If it is an acid chloride, it can be copolymerized with a diamine. (This type of polymer is called a heteroannular chain if only one of the rings in the repeat unit is in the backbone, the polymer is called homoannular.)7 Similarly, the titanium complex shown in 7.17 is copolymerized with diacids or diols.30 Numerous other examples involving ferrocenes are discussed in Chapter 6. 

A first example of an enantioselective catalytic diamination of alkenes has been developed, which employs enantiopure titanium complexes as catalysts and bis(r- butylimido)dioxoosmium(VIII) as the nitrogen source.129... 

Bis(2,4-pentanedionato)oxovana-dium(IV), 5 113-115 Bis(8-quinolinolato)dioxouranium-(VI), and its addition compound with 8-quinolinol, 4 101 Jrans-Bis (thiocyanato)bis (ethylene-diamine)chromium(III) thiocyanate, 2 200, 202 Bis(triphenylgermyl)oxide, 5 78 Bis[tris(2,4-pen tanediono)titanium-(IV) jhexachlorotitanate(I V), 2 119... 

Asymmetric amplification in the diethylzinc addition to aldehydes has been observed with many (3-amino alcohols as catalyst, presumably because of a reservoir effect similar to that discovered by Noyori et al. Asymmetric amplification has also been found for other classes of chiral catalysts—diamines, diols, titanium complexes, etc. The various examples are collected in Table 1. The... 

To avoid secondary reductive steps, low concentrations of the active low-valent metal are advantageous, i.e. the use of catalytic one-electron reduction cycles [31]. Low-valent vanadium species are efficient catalysts for pinacolization. After the primary electron transfer, the oxidized vanadium catalyst can be reduced by Zn(0) or by aluminum [32], TrialkyIsilanes have to be added to decomplex the oxidized vanadium catalyst from the pinacol [33]. The same catalytic system can also be used for the synthesis of 1,2-diamines via coupling of aldimines [34]. Alternatively, a titanium (Il)-samarium system gives the 1,2-diamines with moderate D,L-selectivity [35]. 

More recently the introduction of low-valent transition metal and lanthanoid based reducing systems, especially those based on titanium, has provided dramatic advances in efficiency and selectivity. It is now possible to select appropriate conditions for efficient coupling of all types of carbonyl compounds, often with high chemo-, regio- and stereo-selectivity. Moreover, imino- and thio-carbonyl derivatives are also coupled via pinacolic methodology. The coupling of imines to 1,2-diamines is particularly effective, with excellent control of vicinal stereochemistry. 

Alkenes. The low-valent titanium species is useful for defunctionalization of l-(2-hydroxyalkyl)benzotriazoles. The reagent is activated by the addition of stoichiometric amounts of iodine for the McMuny coupling of carbonyl compoimds. 1,2-Diamines Reductive dimerization of imines affords diamines which are valuable ligands. 

The use of chiral diamine 60 with Sn(OTf)2/Bu2Sn(OAc)2 promotes Mukaiya-ma aldol reactions, and such an example was used in a recent synthesis of Tax-ol , in which adduct 61 was obtained with 99% ds and 96% ee (Scheme 9-20) [42J. Other notable contributions to this field have been made using dienolate chemistry. For example, the titanium complex 62 promotes aldol reactions of silyl dienol ethers (Scheme 9-21). Products 63 and ent-63 were then used in the synthesis of macrolactin A (64) [43],... 

Cyclopropaniminium salts have been prepared in solution from cyclopropane-1,1-diamines by addition of methyl fluorosulfate, - bromine in liquid sulfur dioxide or dimethylchloronium tetrafluoroantimonate in liquid sulfur dioxide. Bicyclo[4.1.0]heptaniminium salts were obtained in fluorosulfonic acid at — 60 °C from a bicyclo[4.1.0]heptanone aminal or hemiaminal precursor or by the reaction of the corresponding aminal and methyl fluorosulfate in chloroform. A free cyclopropaniminium ion in solution also was assumed to be generated by the interaction of cyclopropanone hemiaminal with titanium(IV) chloride at — 78°C in di-chloromethane. ... 

Special considerations chemical composition of filler surface affects nucleation of filler traces of heavy metals decrease thermal stability and cause discoloration siuface free energy of fillers determines interaction large difference in thermal properties of fillers and polymer may cause stress hydrotalcite is used as acid neutralizer with stabilizing packages anatase titanium dioxide decreases UV stability presence of transition metals (Ni, Zn, Fe, Co) affects thermal and UV stability calcium carbonate and talc were found to immobilize HALS stabilizers in PP with organic masterbatches such as ethylene diamine phosphate V-0 classification can be obtained with 20-25 wt%, at the same time tensile strength and impact strength are substantially reduced... 

---