Subject alkoxides

An aryloxypyrimi done has been described as an anti ulcer agent this activity is of note since the agent does not bear any structural relation to better known anti ulcer drugs. Displacement of halogen on the acetal of chloro-acetaldehyde by alkoxide from m-cresol gives the intermediate This affords enaminoaldehyde when subjected... 

Because the Williamson synthesis is an S 2 reaction, it is subject to all the usual constraints, as discussed in Section 11.2. Primary halides and tosylates work best because competitive E2 elimination can occur with more hindered substrates. Unsymmetrical ethers should therefore be synthesized by reaction between the more hindered alkoxide partner and less hindered halide partner rather than vice versa. For example, terf-butyl methyl ether, a substance used in the 1990s as an octane booster in gasoline, is best prepared by reaction of tert-butoxide ion. with iodomethane rather than by reaction of methoxide ion with 2-chloro-2-methylpropane. 

The preparation of a functional segmented block copolymer was also investigated (scheme ll).15 First hydroboration polymerization of the oligomer using thexylborane was carried out. Then the obtained organoboron polymer was subjected to a chain-transformation reaction (DCME rearrangement). DCME and lithium alkoxide of 3-ethyl-3-pentanol in hexane was added to a THF solution of the polymer at 0°C. 

Vinylidenecarbene or allenylidene3 (R)2C=C=C has a lance-shaped, unsubstituted and sp-hybridized carbene center and, therefore, will not be easily subject to steric hindrance in its insertion reactions. On this assumption, (2-methyljpropenylidenecarbene or its carbenoid was chosen as a prototype of typical vinylidenecarbenes and its insertion reaction with several different types of alkoxides was investigated by employing two methods (A and B, Scheme 10) for carbene generation.20 The insertion products 20 were obtained almost exclusively except lithium allyloxide (Table 4, entry 10).21 By-products such as propargyl ether and allenyl ether were not formed at all. To be noted here, in... 

This section diverges from the main subject but, being studied together with the insertion of (phenylthio)carbenes with alkoxides, is worth describing here due to its synthetic versatility as C-C bond forming reactions. 

In order to model the oxygenation of vitamin K in its hydroquinone form, a naph-thohydroquinone derivative with a 1-hydroxy group and 4-ethyl ether was prepared and its alkoxide subjected to oxidation with molecular oxygen. Products consistent with two possible mechanisms were isolated, the epoxy-quinone which must derive from a peroxy anion intermediate at the 4-position, and a 2-hydroxy product which... 

Meerwein-Pondorf-Verley reduction, discovered in the 1920s, is the transfer hydrogenation of carbonyl compounds by alcohols, catalyzed by basic metal compounds (e.g., alkoxides) [56-58]. The same reaction viewed as oxidation of alcohols [59] is called Oppenauer oxidation. Suitable catalysts include homogeneous as well as heterogeneous systems, containing a wide variety of metals like Li, Mg, Ca, Al, Ti, 2r and lanthanides. The subject has been reviewed recently [22]. In this review we will concentrate on homogeneous catalysis by aluminium. Most aluminium alkoxides will catalyze MPV reduction. 

A similar mechanism is thought to be involved when functionalized dihalocyclopropanes are treated with sodium alkoxides as well as thiophenolates or subjected to the influence of potassium hydroxide in methanol. 

Chloro alkoxide formation is essentially complete at this time and can be conveniently monitored by quenching a small aliquot and subjecting it to GLC analysis. Using a 5(1 m x 0. mm OV-1 capillary column at 110 C and a flow rate of 0.87 mL/m1n H-, earner) the submitters found retention times of 3.2 min for 2-chlorocyclohexanone and 6.7 min and 7.2 min for trans- and cis-1-propynyl-2-chlorocyclohexanols, respect vely. 

Dihydroxybenzene derivatives readily form complexes of the type [Pd(02CeH3R)(PPh3)2].178,179 The increased acidity of aromatic alcohols compared with aliphatic alcohols combined with the chelate effect makes these compounds much more stable than alkoxide complexes. Their stability is such that they can be subjected to further reactions involving the side chain group R to generate compounds suitable for use as indicators for immunoassay.178... 

In 1976, Ueno and Okawara highlighted the fact that no oxidation of primary saturated alcohols to aldehydes via tin alkoxides had been reported in the literature and published a procedure for the selective oxidation of secondary alcohols.25 Interestingly, rather than performing the oxidation on pre-formed tin alkoxides, these researchers subjected a mixture of the diol and (Bu3Sn)20 in CH2C12 to the action of Br2. Regardless of the fact that no complete formation of tin alkoxides is secured and no HBr quencher is added, this method may provide useful yields of hydroxyketones during the selective oxidation of diols.26... 

Therefore, in this book we do not by any means intend to provide a comprehensive treatise on the subject. The aim of this chapter is rather to show a few illustrations of the application ofmetal alkoxides in the synthesis of complex oxides. 

A much more extensive investigation of the effect of alkalies has been made in the case of polysaccharides, especially cellulose this is understandable in view of the industrial importance of mercerization, of the viscose process, and of cellulose ethers. Various complexes have been reported for cellulose and alkalies depending upon the nature of the alkali, upon its concentration, upon the washing treatment used, and upon the pretreatment of the cellulose. A discussion of this subject has been published by Nicoll and Conaway.84 There is general agreement on the formation of several compounds, which are susceptible to hydrolysis. The question as to whether these compounds are molecular complexes (XLVII), true alkoxides (XLVIII), or an equilibrium mixture of the two has not been answered. In recent studies Lauer65 has reached... 

The reaction of basic ZnEt2 with pyrrolidine norephedrine 10 and one equivalent of trifluoroethanol as auxiliary ligand leads to the chiral zinc alkoxide 309 under loss of ethane after deprotonation of the hydroxy groups of 10 and trifluoro ethanol as additive. 30 is not isolated but subjected to addition of cyclopropyl acetylene magnesium... 

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