Aryloxides

Some cleavage takes place even if the phenoHc hydroxyl is blocked as an ether link to another phenylpropane unit and quinonemethide formation is prevented. If the a- or y-carbon hydroxyl is free, alkaH-catalyzed neighboring-group attack can take place with epoxide formation and P-aryloxide elimination. In other reactions, blocked phenoHc units are degraded if an a-carbonyl group is present. 

Oxygen-Gontaining Organics. Neutral and anionic oxygen-containing organic molecules form complexes with thorium. Recent work has focused on alkoxides (72), aryloxides, and carboxylates however, complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates are also well known. 

Zirconium dichiorohis(dimethylamide) [87227-57-4] ZrCl2[N(CH2)2]2 h made direcdy from methylamine and zirconium tetrachloride but all of the halogens can be substituted by treating zirconium tetrachloride with the appropriate lithium alkylamide (229). Zirconium arylamines are made from zirconium alkoxides which first are converted to aryloxides (230). 

The general formula for boric acid esters is B(OR)2. The lower molecular weight esters such as methyl, ethyl, and phenyl are most commonly referred to as methyl borate [121 -43-7] ethyl borate [130-46-9J, and phenyl borate [1095-03-0] respectively. Some of the most common boric acid esters used in industrial appHcations are Hsted in Table 1. The nomenclature in the boric acid ester series can be confusing. The lUPAC committee on boron chemistry has suggested using trialkoxy- and triaryloxyboranes (5) for compounds usually referred to as boric acid esters, trialkyl (or aryl) borates, trialkyl (or aryl) orthoborates, alkyl (or aryl) borates, alkyl (or aryl) orthoborates, and in the older Hterature as boron alkoxides and aryloxides. CycHc boric acid esters, which are trimeric derivatives of metaboric acid (HBO2), are known as boroxines (1). 

Phosphazene polymers are normally made in a two-step process. First, hexachlorocyclotriphosphazene [940-71 -6J, trimer (1), is polymerized in bulk to poly(dichlorophosphazene) [26085-02-9], chloropolymer (2). The chloropolymer is then dissolved and reprecipitated to remove unreacted trimer. After redissolving, nucleophilic substitution on (2) with alkyl or aryloxides provides the desired product (3). 

Fluorme replacement m condensedpolyfluoroaromatics can be a complicated process In perfluoroanihracene the fluonne reactivity toward replacement by methoxide foQows the order 2-F > 9-F [14], whereas in perfluoropyrene, the reactivity decreases in the senes 1-F > 3-F > 6-F> 8-F [75] In decafluoro-l,4-di-hydronaphlhalene, the 6-fluorme is most easily replaced [75] (equation 10) All fluonne atoms in perfluoronaphthalene are replaced by alkoxide or aryloxide with Al, 7 -dimethylimidazolidm-2 one (DMI) as the solvent [16] (equation 11)... 

The stereochemistry of Mg and the heavier alkaline earth metals is more flexible than that of Be and, in addition to occasional compounds which feature low coordination numbers (2, 3 and 4), there are many examples of 6, 8 and 12 coordination, some with 7, 9 or 10 coordination, and even some with coordination numbers as high as 22 or 24, as in SrCdn, BaCdn and (Ca, Sr or Ba)Zni3. " Strontium is 5-coordinate on the hemisolvate [Sr(OC6H2Bu3)2(thf)3]. jthf which features a distorted trigonal bipyramidal structure with the two aryloxides in equatorial positions. ... 

The alkoxides and aryloxides, particularly of yttrium have excited recent interest. This is because of their potential use in the production of electronic and ceramic materials,in particular high temperature superconductors, by the deposition of pure oxides (metallo-organic chemical vapour deposition, MOCVD). They are moisture sensitive but mostly polymeric and involatile and so attempts have been made to inhibit polymerization and produce the required volatility by using bulky alkoxide ligands. M(OR)3, R = 2,6-di-terr-butyl-4-methylphenoxide, are indeed 3-coordinate (pyramidal) monomers but still not sufficiently volatile. More success has been achieved with fluorinated alkoxides, prepared by reacting the parent alcohols with the metal tris-(bis-trimethylsilylamides) ... 

Scandium, tetrakis(tropolone)-stereochemistry, 1,94 Scandium, tris(acetylacetone)-structure, 1. 65, 68 Scandium, tris(tropolonate)-structure, 1,68 Scandium aryloxides spectroscopy, 2, 346 Scandium chloride... 

The low spin aryliron complexes Fe(Por)Ar behave differently than their alkyl counterparts toward oxygen. In chloroform the products of the reaction of Fe(Por)Ar with O2 are the iron(IV) alkyl Fe(Por)Ar] and Fe(Por)Cl, while in toluene the aryloxide complexes Fe(Por)OAr are formed with no direct evidence for the formation of arylperoxo intermediates."" The high spin iron(lll) alkynyl complexes which have more ionic character in the Fe—C bond do not react with oxygen, and the order of reactivity of organoiron(lll) complexes toward O2 is given by Fe(Por)(alkyl) > Fe(Por)(aryl) > Fe(Por)(C=CR). ... 

Sone, T., Iwata, M., Kasuga, N. and Komiya, S. (1991) Drmethylgod(III) aryloxides and alkoxides having a triphenylphosphrne ligand. Chemistry Letters, 20, 1949. 

One limitation of this methodology is that unprotected terminal alkynes are incompatible with the strongly basic ethyl zinc reagents required for this reaction. Iivinghouse and coworkers found that a similar Ti(IV)tetra-aryloxide/cyclohexylmagnesium chloride system catalytically cycloisomer-ized dienes to methylenecyclopentanes 63 with the formation of some reduced product 64 (Eq. 8) [35]. 

Metal-Oxygen Bond Lengths, M—O—C Angles, and Torsion Angles for Three-Coordinate Aluminum and Gallium Alkoxides and Aryloxides... 

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