Hydroxyalkylation, and

The last group of reactions uses ring opening of carbonyl or 1-hydroxyalkyl substituted cyclopropanes, which operate as a -synthons. d -Synthons, e.g. hydroxide or halides, yield 1,4-disubstituted products (E. Wenkert, 1970 A). (1-Hydroxyalkyl)- and (1-haloalkyl)-cyclopropanes are rearranged to homoallylic halides, e.g. in Julia s method of terpene synthesis (M. Julia, 1961, 1974 S.F. Brady, I968 J.P. McCormick, 1975). 

In a similar way, dl-2-(q-hydroxyalkyl)- and 2-(a-alkoxycarbonyl)-4-methyl-5-(/3-hydroxyethyl)thiazoles were synthetized from the corresponding thioamides and 4-hydroxy-3-bromo-2-pentanone (615). 

Primary cycloaUphatic amines react with phosgene to form isocyanates. Reaction of isocyanates with primary and secondary amines forms ureas. Dehydration of ureas or dehydrosulfuri2ation of thioureas results in carhodiimides. The nucleophilicity that deterrnines rapid amine reactivity with acid chlorides and isocyanates also promotes epoxide ring opening to form hydroxyalkyl- and dihydroxyalkylaniines. Michael addition to acrylonitrile yields stable cyanoethylcycloalkylarnines. 

These products are characterized in terms of moles of substitution (MS) rather than DS. MS is used because the reaction of an ethylene oxide or propylene oxide molecule with ceUulose leads to the formation of a new hydroxyl group with which another alkylene oxide molecule can react to form an oligomeric side chain. Therefore, theoreticaUy, there is no limit to the moles of substituent that can be added to each D-glucopyranosyl unit. MS denotes the average number of moles of alkylene oxide that has reacted per D-glucopyranosyl unit. Because starch is usuaUy derivatized to a considerably lesser degree than is ceUulose, formation of substituent poly(alkylene oxide) chains does not usuaUy occur when starch is hydroxyalkylated and DS = MS. 

Nonionic polyethylene glycol 2-hydroxyalkyl and 3-alkoxy-2-hydroxyalkyl phosphate surfactants were prepared by the reaction of a polyethylene glycol... 

We present the enthalpies of disproportionation of aminyl radicals with hydroxyalkyl and alkyl peroxyl radicals in Table 16.2 [22-24],... 

By a procedure analogous to that used for the production of benzoic acids, it is possible to produce benzolactones and benzolactams (Scheme 8.10) in good yield (60-95%) from suitable 2-(hydroxyalkyl)- and 2-(aminoalkyl)bromobenzenes. The... 

The fact that pyromeconic acid and allomaltol were only available with difficulty meant that direct synthesis of certain 3-hydroxy-4-pyridinones was not possible. However the demonstration that some of these compounds were accessible from maltol or ethylmaltol by functionalizing the position adjacent to the ring-oxygen by an aldol condensation and N-oxide intermediates led to the preparation of 2-(l -hydroxyalkyl) and 2-amido derivatives with usefully high affinities for Fe + (70). 

The t>/X t>-hydroxyalkylation and cyclization of aminopyridines has given rise to a large range of heterocycles, including naphthyridines, dihydronaphthyridines, and tetrahydronaphthyridines <1999S1893>. 

The class of neutral ligands includes phosphanes with hydroxyalkyl and polyether substituents and sugar derivatives of phosphanes. 

These redox chain reactions, which cycle iron(II) and iron(III), have advantages over methods that use stoichiometric quantities of oxidants because the hydroxymethyl radical is also a good reductant and, at high oxidant concentrations, it may be oxidized more rapidly than it adds to (72). The disadvantage of this type of reaction is that the initial radical is generated by a relatively non-selective hydrogen atom abstraction reaction. To be efficient, the H-donor must be used in large excess it is often a cosolvent. Nonetheless, this is a very practical method to prepare hydroxyalkylated and acylated heteroaromatic and related derivatives. 

The hydroxyalkyl- and aminoalkylpyridines are also almost totally unexplored. The oxidation of various hydroxyalkylpyridines was studied by voltammetry at a platinum anode.122 The ring substituents had no effect on the position of the discharge wave. Oxidation of the metal-complexed amine 147 to the imine 148 was quantitative.209... 

Purines. The reactions of purines with a-hydroxyalkyl and a-alkoxyalkyl radicals have been most intensively investigated (Elad et al. 1969 Steinmaus et al. 1969, 1971 Elad and Salomon 1971 Leonov et al. 1973 Salomon and Elad 1973 Leonov and Elad 1974a,b Moorthy and Hayon 1975 Frimer et al. 1976 Aravin-dakumar et al. 1994), but the reactions of radicals derived from amino acids (Elad and Rosenthal 1969 Elad et al. 1969 Elad and Salomon 1971 Poupko et al. 1973 Salomon and Elad 1974) and amines (Elad and Salomon 1971 Salomon and Elad 1973) and of the methyl radical (Maeda et al. 1974) are also reported (for a review of the older work see Elad 1976). 

Heterobimetallic homogeneous catalysts [e.g. (12)] have been developed26 for the alkylation of a range of aromatic compounds by n-activated alcohols. The superior electrophilicity is attributed to the high-valent T-Sn core in the structures. A review has appeared of reactions involving the hydroxyalkylation and cycloalkylation of arenes by hydrofurans, lactones, and unsaturated acids 27... 

Hydroxyalkyl and Hydroxyalkyl Aryl Ethers of Dextran as Emulsifying Agents... 

Mention has already been made of the numerous effects attendant upon chemical substitutions on the polysaccharide linear chain. Natural branches impart a dispersion stability to amylopectin that is not afforded amylose. One only has to compare cellulose ethers, deesterified chitin, and the lysis product of protopectin with the underivatized parent compound to appreciate the impact of chemical substituents on functionality. The loosening of compact, parallel structures with alkyl, hydroxyalkyl, and alkoxyl groups facilitates hydration and transforms insoluble, refractory polysaccharides to soluble, reactive polysaccharides. Not only do these substituents obstruct the crystallization tendency, they almost always confer secondary functionalities like q enhancement and foam, suspension, and freeze-thaw stabilization. 

More recently, models were developed to achieve the elimination of the template under milder conditions. The first relies on the preparation of a dialkyl carbonate system by polycondensation/hydrolysis of the corresponding precursor family 26. Thermal treatment of a non-porous xerogel of 26 at 250-350 °C results in the simultaneous elimination of CO2 and hybrid materials with residual hydroxyalkyl and olefinic functions according to Scheme 18. It is interesting to note that this approach also allows the preparation of materials which cannot be prepared by other routes, such as direct polycondensation of the corresponding allyl and hydroxyalkyl precursors. 

With conjugated dienes cohalogenation proceeds also via a 1,4 addition. A recently reported reaction is the Pd(II)-catalyzed stereocontrolled oxaspirocyclization of 1-(3-hydroxyalkyl)- and l-(4-hydroxyalkyl)-l,3-cyclohexadiene (equation 60)469. 

These important hydroxyalkyl- and hydroxyarylpyrazines should be considered as regular alcohols or phenols simply because their methods of preparation and their reactions are only minimally affected by the attached pyrazine ring. 

The following illustrative examples have been chosen from many different reaction types. For some specific reactions that are of interest mainly to the fragrance industry, e.g. epoxide rearrangement, reference is made to another chapter in this volume. Moreover, functionalization of aromatic compounds, comprising alkylations, acylations and hydroxyalkylations, and oxidations of phenol or olefins are not dicussed in this chapter, since these topics are covered by other authors. 

By Oxidation of Alkyl-, Styryl-, Hydroxyalkyl-, and Fused Pyrazine Systems... 

Hydroxyalkyl and Epoxyalkyl Acids. Lipase-catalysed acylation of ethyl(l-hydroxyalkyl)phenylphosphinates (249) and (250) afforded a single diastereoisomer of the corresponding acetates (251) in high enantiomeric excess (>98%) (Figure 46). °... 

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