Complexes alkoxides, phenyls

PBD-Modified LiNbOs Precursor. Non-modified LiNbOs (STD-LiNbOs) precursor solutions are prepared from LiOEt and Nb(OEt)s in ethanol (Hirano, 2002). The structure of the precursor was confirmed to consist of a complex alkoxide Li[Nb(OEt)6], which was reported by Eichorst et al. (1990) in detail (Eichorst et al., 1990). On the other hand, three types of/6-diketone compounds are selected based upon the number of benzene rings (phenyl groups) in its stmcture. In this case, the coordination of l-phenyl-1,3-butanedione (PBD) to the LiNbOs precursor is confirmed by UV spectra. The similar coordination is also realized in 2,4-pentanedione (PD)- and 1,3-diphenyl-1,3-propanedione (DPPD)-modified LiNbOs precursors, which was confirmed by UV-spectra. The proposed structures of these d-diketone modified LiNbOs precursors are shown in Figure 17-1. 

The asymmetric oxidation of sulphides to chiral sulphoxides with t-butyl hydroperoxide is catalysed very effectively by a titanium complex, produced in situ from a titanium alkoxide and a chiral binaphthol, with enantioselectivities up to 96%342. The Sharpless oxidation of aryl cinnamyl selenides 217 gave a chiral 1-phenyl-2-propen-l-ol (218) via an asymmetric [2,3] sigmatropic shift (Scheme 4)343. For other titanium-catalysed epoxidations, see Section V.D.l on vanadium catalysis. 

R = alkyl, aryl) undergoes insertion reactions with C02, COS, CS2, and CSe2 to form carbamate complexes and reacts with alcohols to form alkoxide complexes. The structural motif of the amido complexes is highly dependent on the steric bulk of the R group. When R = phenyl, the complex is... 

The tricarbonylchromium entity promotes ipso-Smiles rearrangement of the O-phenyl derivatives of ephedrine and pseudoephedrine to the N-phenyl derivatives [32]. Indeed, treatment of the sodium alkoxide derived from (1 R,2S)-ephedrine with fluorobenzene complex... 

Ebelman and Bouquet prepared the first examples of boric acid esters in 1846 from boron trichloride and alcohols. Literature reviews of this subject are available. B The general class of boric acid esters includes the more common orthoboric acid based trialkoxy- and triaryloxyboranes, B(0R)3 (1), and also the cyclic boroxins, (ROBO)3, which are based on metaboric acid (2). The boranes can be simple trialkoxyboranes, cyclic diol derivatives, or more complex trigonal and tetrahedral derivatives of polyhydric alcohols. Nomenclature is confusing in boric acid ester chemistry. Many trialkoxy- and triaryloxyboranes such as methyl, ethyl, and phenyl are commonly referred to simply as methyl, ethyl, and phenyl borates. The lUPAC boron nomenclature committee has recommended the use of trialkoxy- and triaryloxyboranes for these compounds, but they are referred to in the literature as boric acid esters, trialkoxy and triaryloxy borates, trialkyl and triaryl borates or orthoborates, and boron alkoxides and aryloxides. The lUPAC nomenclature will be used in this review except for relatively common compounds such as methyl borate. Boroxins are also referred to as metaborates and more commonly as boroxines. Boroxin is preferred by the lUPAC nomenclature committee and will be used in this review. 

Orthometallation of substituted arenes has been reviewed. The ortho-directing ability of substituents in ( ) -arene)Cr(CO)3 complexes decreases as F > CONHR > NHCOR > CH2NR2 OMe ) > CH20Me. Heavier alkali metal arenes can be formed from the reaction of phenyl lithium with sodium or potassium alkoxides. 

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