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Hydroxyalkyl Types

Examples with NH3 as the leaving group are a-hydroxyalkyl-type radicals from / -amino alcohols [68] or from serine (R — H) or threonine (R = Me) ... [Pg.1168]

Polymeric OC-Oxygen-Substituted Peroxides. Polymeric peroxides (3) are formed from the following reactions ketone and aldehydes with hydrogen peroxide, ozonization of unsaturated compounds, and dehydration of a-hydroxyalkyl hydroperoxides consequendy, a variety of polymeric peroxides of this type exist. Polymeric peroxides are generally viscous Hquids or amorphous soHds, are difficult to characterize, and are prone to explosive decomp o sition. [Pg.116]

Properties. MethylceUulose [9004-67-5] (MC) and its alkylene oxide derivatives hydroxypropylmethylceUulose [9004-65-3] (HPMC), hydroxyethylmethylceUulose [9032-42-2] (HEMC), and hydroxybutyknethylcellulose [9041-56-9] (HBMC) are nonionic, surface-active, water-soluble polymers. Each type of derivative is available in a range of methyl and hydroxyalkyl substitutions. The extent and uniformity of the methyl substitution and the specific type of hydroxyalkyl substituent affect the solubifity, surface activity, thermal gelation, and other properties of the polymers in solution. [Pg.276]

All example for the preparation of diastereomerically pure, but racemic, carbonylchloro(cy-clopentadienyl)-t 3-[l-(l-hydroxyalkyl)allyl]nitrosomolybdenum complexes of type 21 (several examples)6 via the -allyllricarbonyltcyclopentadienylimolybdenum complex 19 is given ... [Pg.448]

The method is not restricted to secondary aryl alcohols and very good results were also obtained for secondary diols [39], a- and S-hydroxyalkylphosphonates [40], 2-hydroxyalkyl sulfones [41], allylic alcohols [42], S-halo alcohols [43], aromatic chlorohydrins [44], functionalized y-hydroxy amides [45], 1,2-diarylethanols [46], and primary amines [47]. Recently, the synthetic potential of this method was expanded by application of an air-stable and recyclable racemization catalyst that is applicable to alcohol DKR at room temperature [48]. The catalyst type is not limited to organometallic ruthenium compounds. Recent report indicates that the in situ racemization of amines with thiyl radicals can also be combined with enzymatic acylation of amines [49]. It is clear that, in the future, other types of catalytic racemization processes will be used together with enzymatic processes. [Pg.105]

C-chiral hydroxy phosphorus derivatives, which have been described so far in the literature, are secondary alcohols. Thus, the syntheses of non-racemic compounds of this type comprise two main approaches (cf. C-chiral hydroxyalkyl sulfones. Section 2.2) asymmetric reduction of the corresponding keto derivatives and resolution of racemic hydroxyalkanephosphorus substrates. [Pg.172]

Two types of addition to pyrimidine bases appear to exist. The first, the formation of pyrimidine photohydrates, has been the subject of a detailed review.251 Results suggest that two reactive species may be involved in the photohydration of 1,3-dimethyluracil.252 A recent example of this type of addition is to be found in 6-azacytosine (308) which forms a photohydration product (309) analogous to that found in cytosine.253 The second type of addition proceeds via radical intermediates and is illustrated by the addition of propan-2-ol to the trimethylcytosine 310 to give the alcohol 311 and the dihydro derivative 312.254 The same adduct is formed by a di-tert-butyl peroxide-initiated free radical reaction. Numerous other photoreactions involving the formation by hydrogen abstraction of hydroxyalkyl radicals and their subsequent addition to heterocycles have been reported. Systems studied include 3-aminopyrido[4,3-c]us-triazine,255 02,2 -anhydrouri-dine,256 and sym-triazolo[4,3-fe]pyridazine.257 The photoaddition of alcohols to purines is also a well-documented transformation. The stereospecific addition of methanol to the purine 313, for example, is an important step in the synthesis of coformycin.258 These reactions are frequently more... [Pg.290]

The interaction of carboxyalkylphosphines with aldehydes belongs to the same type of reactions reported above. The phenyl-(a-hydroxyalkyl)-carboxyalkylphosphine products transform into phosphorus-containing lactones (10) and water [Eq. (8)] [72JPR66 73ZC(13)310]. [Pg.63]

Boryl-borate tautomerism This type of tautomerism is observed for boryloxyalkylphosphines (101), (102) possessing a hydroxyalkyl group and electron-acceptor substituents at the a-carbon atom [Eq. (88)] (851ZV1102 90IZV1133). Mutual transformations take place rapidly and the equivalency of methyne protons in NMR spectra serves as evidence of tautomerism. In the crystalline state these compounds exist in form A. The considerable influence of the nature of the solvent (-4 ppm in DMFA - 10 ppm in C6H6) on the position of the signal in the MP NMR spectrum provides evidence in favor of tautomerism. [Pg.98]

Bicyclic-monocyclic ion-complex tautomerism The introduction of functional groups onto the substituent at carbon, nitrogen, or phosphorus atoms increases the number of possible types of ion-complex tautomerism. For example, the presence of one more hydroxyalkyl group at the phosphorus atom results in bicyclic-monocyclic tautomerism [Eq. (91)] (85IZV469, 85IZV1102 89IZV946). [Pg.101]

Aldol-type reactions of nitrones (303) occur with electron-deficient ketones, such as a-keto esters, a, 3-diketones, and trifluoromethyl ketones. These reactions are catalyzed by secondary amines. The use of chiral cyclic amines A1-A7 leads to a-(2-hydroxyalkyl)nitrones (304) in moderate yields and rather high optical purity (Scheme 2.120) (381). The mechanism of the nitrone-aldol reaction of iV-methyl-C-ethyl nitrone with dimethyl ketomalonate in the absence and presence of L- proline has been studied by using density functional theory (DFT) (544). [Pg.228]

A stereoselective tandem iodination and aldol-type condensation has been described for the reaction of methyl propiolate and carbonyl compounds in the presence of a stoichiometric amount of tetra-n-butylammonium iodide and zirconium chloride to yield Z-3-iodo-2-(l-hydroxyalkyl)propenoates, as the major products [48]. No reaction occurs in the absence of the Lewis acid. There does not appear to be any control on the chirality of the hydroxyl centre. [Pg.529]

Smith and Liu have successfully prepared an unsymmetrical analog of a Katsui-type salen ligand possessing a hydroxyalkyl group in the 6-position, which facilitated the formation of an ester Hnkage to a polystyrene carboxyl chloride resin (Figure 5.19) derived from Merrifield s resin (chloromethylated polystyrene,... [Pg.193]

Thiamine diphosphate (TPP, 3), in cooperation with enzymes, is able to activate aldehydes or ketones as hydroxyalkyl groups and then to pass them on to other molecules. This type of transfer is important in the transketo-lase reaction, for example (see p. 152). Hydroxyalkyl residues also arise in the decarboxylation of 0x0 acids. In this case, they are released as aldehydes or transferred to lipoamide residues of 2-oxoacid dehydrogenases (see p. 134). The functional component of TPP is the sulfur- and nitrogen-containing thiazole ring. [Pg.106]

SchOllkopf et al. reacted lithiated isocyanides with epoxides to obtain 3-hydroxyalkyl isocyanides. The reaction was also performed with cyclohexene oxide, and the hydroxyisocyanate formed was cyclized to oxazines with copper(I) oxide, resulting in a diastereomeric mixture of 174 and 175 (76LA2105 86AG755). Irradiation of aliphatic dieneamides yielded a variety of dihydrooxazines of type 167 (88T1959). [Pg.377]

Acid-catalyzed intramolecular attack of nucleophilic hydroperoxide function on an oxirane ring results in formation of 3-(l-hydroxyalkyl)endoperoxides. For example, epoxidation of unsaturated hydroperoxide 320 affords oxirane-hydroperoxide 321 (66%), which through acid-catalyzed regioselective cyclization gives 1,2-dioxolane 322 (70%) (Scheme 79) . This type of reaction is applicable also to a more complex epoxide-hydroperoxide such as 323, which cyclizes to polyfunctionalized 5-membered cyclic... [Pg.236]

Described below is one of the three types of syntheses of metallacyclic a-hydroxyalkyl complexes that we have developed.3 It is simple to execute and employs two starting materials that have been reported in previous volumes of Inorganic Syntheses. 5... [Pg.169]

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. [Pg.768]


See other pages where Hydroxyalkyl Types is mentioned: [Pg.47]    [Pg.86]    [Pg.47]    [Pg.86]    [Pg.56]    [Pg.322]    [Pg.323]    [Pg.91]    [Pg.161]    [Pg.412]    [Pg.322]    [Pg.357]    [Pg.310]    [Pg.87]    [Pg.89]    [Pg.97]    [Pg.13]    [Pg.270]    [Pg.275]    [Pg.533]    [Pg.366]    [Pg.345]    [Pg.36]    [Pg.563]    [Pg.43]    [Pg.52]    [Pg.279]    [Pg.130]    [Pg.265]    [Pg.323]   


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