A-Alkoxyl groups

Alkoxyl tion. The nucleophilic replacement of an aromatic halogen atom by an alkoxy group is an important process, especially for production of methoxy-containing iatermediates. Alkoxylation is preferred to alkylation of the phenol wherever possible, and typically iavolves the iateraction of a chloro compound, activated by a nitro group, with the appropriate alcohol ia the presence of alkaU. Careful control of alkaU concentration and temperature are essential, and formation of by-product azoxy compounds is avoided by passiag air through the reaction mixture (21). 

Alteration of positional selectivity will result from built-in solvation of the transition state by an adjacent carboxyl-related function.Aminations will be so affected by carboxyl, carboxylate ion, carboalkoxy and less so by carboxamido groups (cf. Section I,D,2,b, structure 12.) Other substitutions such as alkoxylations can be so affected by carboxamido and amidino groups (cf. Section I,D, 2,b, structure 14). The effect of the cyclic hydrogen-bonded form (63) of 2-carboxamidopyridine on the reactivity of a leaving group is not known. 

For the Birch reduction of mono-substituted aromatic substrates the substituents generally influence the course of the reduction process. Electron-donating substituents (e.g. alkyl or alkoxyl groups) lead to products with the substituent located at a double bond carbon center. The reduction of methoxybenzene (anisole) 7 yields 1-methoxycyclohexa-1,4-diene 8 ... 

Several determinations of the number of propagation centers by the quenching technique have been carried out (98, 111). As a quenching agent methanol, labeled C14 in the alkoxyl group, proved to be suitable in this case. The number of active centers determined by this technique at relatively low polymerization rates (up to 5 X 102 g C2H4/mmole Cr hr at 75° and about 16 kg/cm2) (98, 111, 168) in catalysts on silica was about... 

The alkoxyl group OR is not a leaving group, so these compounds must be converted to the conjugate acids before they can be hydrolyzed. Although 100% sulfuric acid and other concentrated strong acids readily cleave simple ethers, the only acids used preparatively for this purpose are HBr and HI (10-71). However, acetals, ketals, and ortho esters are easily cleaved by dilute acids. These compounds are... 

The situation with 7V-acyloxy-/V-alkoxyureas and carbamates is similar although infrared data were mostly determined by liquid film or condensed phase (KBr/nujol mull).52,131 However, the limited data for V-acyloxy-TV-alkoxyureas (Table 2, entries 69-72) give amide carbonyl frequencies ca. 1730 cm-1 that are raised by some 37-40 cm-1 by acyloxylation. Values for carbamates (Table 2, entries 73-77) are higher (mostly 1780 cm-1) but are raised to a lesser extent (10-20 cm-1) relative to their parent carbamates. Clearly, carbonyl vibrational frequencies will be influenced strongly by the adjacent amino or alkoxyl group in both analogues. 

These rearrangement processes are characterised by a transition state in which the alkoxyl group migrates from the amide nitrogen to the carbonyl carbon (Fig. 17a) and therefore involves HEteroatom Rearrangements On Nitrogen the HERON... 

The physical and spectroscopic properties of /V-acyloxy-A-alkoxyamides confirm pyramidality at nitrogen and the disconnection of the nitrogen lone pair from the amide carbonyl. The presence of an acyloxyl and an alkoxyl group at nitrogen also results in an anomeric interaction between the oxygens, which is facilitated by the sp3-hybridised nitrogen. Experimental observations, including X-ray analysis are fully supported by results from computational chemistry. 

Other functional groups which have a heteroatom rather than a hydroxyl group capable of directing the hydrogenation include alkoxyl, alkoxycarbonyl, carboxylate, amide, carbamate, and sulfoxide. The alkoxy unit efficiently coordinates to cationic iridium or rhodium complexes, and high diastereoselectivity is induced in the reactions of cyclic substrates (Table 21.3, entries 11-13) [25, 28]. An acetal affords much lower selectivity than the corresponding unsaturated ketone (Table 21.3, entries 14 and 15) [25]. 

Fig. 39.—,3C-N.m.r. Spectra of A, 0-(Carboxymethyl)cellulose (d.s. 0.7), Partially Degraded by Cellulase, in D20 at 30° (R, signal of reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group) and of B, 0-(2-Hydroxyethyl)cellulose (d.s. 0.8), Partly Degraded by Cellulase, in D20 at 30°. (R, signal due to reducing-end residue S represents a 13C nucleus bonded to an alkoxyl group.)...

Large changes in nitrogen hyperfine interaction are brought about by attachment either of alkoxyl groups or of acyl groups to the nitroxide nitrogen. In an alkoxy alkyl nitroxide, aN rises to nearly 30 G, whilst a typical acyl alkyl nitroxide has an aN-value of ca. 8 G, and in diacyl nitroxides this may fall below 5 G (Lemaire and Rassat, 1964). 

This chapter will cover the synthesis, structure and chemical reactivity of various N-heteroatom-substituted hydroxamic esters, anomeric amides in which at least one of the heteroatom substituents at nitrogen is an alkoxyl group. Throughout this review, these will either be referred to as A-substituted hydroxamic esters or as A-substituted-A-alkoxy amides. 

Alkoxyl and acetoxyl protons in A-acetoxy-A-alkoxybenzamides give rise to sharp signals well below room temperature. In contrast, hydroxamic esters usually exhibit line broadened alkoxyl group resonances in their H NMR spectra at or even signihcantly above room temperature" . In toluene-rfg, the benzylic and acetoxyl methyl resonances of A-acetoxy-A-benzyloxybenzamide (100) showed signihcant line broadening below 250 K but remained isochronous down to 190 K. 

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