Substitution by hydroxy

Often, the exact position of tautomeric equilibria (Section III,A,4,a) is uncertain for fused troponoids substituted by hydroxy, mercapto, or amino groups. In such cases the structures preferred by the authors or the most probable tautomeric forms will be used here. 

Cleavage of vie-diols. C—C bonds substituted by hydroxy groups are cleaved by this system to ketones and carboxylic acids in high yield. Di-lerl-diols are cleaved... 

A 2-methylthio group on 4-pyrimidinones and on 6-amino-4-pyrimidinones (135) is displaced by methylamine acetate and by various salts of ammonia and other amines. Similarly, substitution by hydroxy groups occurs in hot aqueous acid with 2-arylthio- or -alkylthio-pyrimidines. Methylthio appears to be a better leaving group than a methoxy group on pyrimidine but not on -triazine. A 2-methylthio group on pyrimidine is stable to many nucleophiles (NH3, OCHs, CHsNH2) but can be displaced by... 

However, other substitution patterns result in decreased activity [75], The dialkylaminoalkyl group on the N-5 atom is essential for activity. Dealkylation or quatemization at the terminal nitrogen leads to almost inactive compounds. Substitution by hydroxy, alkoxy or aralkoxy for the acetoxy function at R3 produces compounds with activity similar to that of diltiazem, as does the replacement of the acetoxy group by longer-chain aliphatic or aromatic acyloxy groups [75]. 

The alkoxy group has been substituted by hydroxy, alkylsulfanyl, amino or hydrazino groups233 234 and can also be substituted by carbon nucleophiles.240... 

Photolysis of 3,5-diphenylanthranil in concentrated hydrochloric acid produces 5-(p-chlorophenyl)-2-aminobenzophenone as expected from a consideration of mesomeric structures (165 R1 = Ph).228 5-Halogeno-3-phenylanthranils under similar conditions yield 3,5-dihalogeno-2-amino-benzophenones, whereas photolysis in concentrated sulfuric acid results in substitution (by hydroxy) and migration of the halogen to give 2-amino-6-halogeno-5-hydroxybenzophenones in 25-35% yield. Irradiation of 3-phenylanthranils in hydrobromic acid is somewhat different in that unsubstituted o-aminobenzophenones are produced in addition to their bromo derivatives.228... 

The U.V., i.r., and H n.m.r. absorptions of 1000 simple aromatic compounds substituted by hydroxy-, methoxy-, and methylenedioxy-groups have been collected as a possible aid to identification of alkaloid degradation products. Homobenzylic and homoallylic spin-spin coupling interactions in some octahydro- and hexahydro-phenanthridines have been discussed. 

Estranes are steroid derivatives with an aromatic A ring. They are devoid of the angular methyl group at C-10. The ring system may be substituted by hydroxy or carbonyl groups. 

In most naturally occurring purines the ring system is substituted by hydroxy and/or amino groups. Frequently glycosides (ribosides and deoxyribosides) are found. 

This nucleus is frequently substituted by hydroxy and amino groups and may carry an aliphatic side chain with one or three C-atoms. 2-Amino-4-hydroxy-pteridines are called pterins. 

Cinnamic acids are phenylpropenic acids. The phenyl ring may be substituted by hydroxy and methoxy groups. The double bond of the side chain may have cis- or trans-configuration. c s- and trans-cinnamic acids are easily interconvertible. 

Stilbenes are ethylene derivatives substituted by two phenyl rings (Table 54). Ring A usually carries two hydroxy groups in m-position, while ring B is substituted by hydroxy and methoxy groups in o-, m- and p-position to the ethylene core. 

The C = C double bond causes dramatic changes in the corrosion-inhibiting property only in the acyl moiety. With the amino acid side chain, the effectiveness is enhanced by the presence of a C = C group only if the vicinal phenyl ring is substituted by hydroxy/methoxy groups. The nitrogen substituent reduces the inhibition capacity. 

The most general methods for the syntheses of 1,2-difunctional molecules are based on the oxidation of carbon-carbon multiple bonds (p. 117) and the opening of oxiranes by hetero atoms (p. 123fl.). There exist, however, also a few useful reactions in which an a - and a d -synthon or two r -synthons are combined. The classical polar reaction is the addition of cyanide anion to carbonyl groups, which leads to a-hydroxynitriles (cyanohydrins). It is used, for example, in Strecker s synthesis of amino acids and in the homologization of monosaccharides. The ff-hydroxy group of a nitrile can be easily substituted by various nucleophiles, the nitrile can be solvolyzed or reduced. Therefore a large variety of terminal difunctional molecules with one additional carbon atom can be made. Equally versatile are a-methylsulfinyl ketones (H.G. Hauthal, 1971 T. Durst, 1979 O. DeLucchi, 1991), which are available from acid chlorides or esters and the dimsyl anion. Carbanions of these compounds can also be used for the synthesis of 1,4-dicarbonyl compounds (p. 65f.). 

Trichloroacetonitrile reacts with glycosidic hydroxy groups of protected sugars to form glycosyl trichloroacetimidates (R. R. Schmidt, 1980, 1984,1985,1986 B. Wegmann, 1988). The imidate is substituted by alcohols in the presence of trimethylsilyl trifluoromethanesulfonate... 

A.mina.tlon. Amination describes the introduction of amino groups into aromatic molecules by reaction of ammonia or an amine with suitably substituted halogeno, hydroxy, or sulfonated derivatives by nucleophilic displacement. Although reaction and operational conditions vary, the process always involves the heating of the appropriate precursor with excess aqueous ammonia or amine under pressure. 

A great number of N-substituted 4-hydroxy-3-nitro-l,8-naphthyridin-2 (IH)-ones are obtained by reaction of N-substituted azaisatoic anhydrides with ethyl nitroacetate carbanion (Section II,A,4,a). A very specific method, more recently developed, is that of the inverse Diels-Alder method, involving the reactions of enamines with 5-nitropyrimidine (Section II,A,4,b). 

Reaction of 8-substituted 3-[2-(4-methoxybenzyl)-2//-tetrazol-5-yl]-4//-pyrido[l,2-u]pyrimidin-4-ones with CF3COOH for 2 days at room temperature gave 3-(2//-tetrazol-5-yl) derivatives (OlMIPl). The cyano group of a 3-(8-substituted 2-hydroxy-4-oxo-4//-pyrido[l,2-u]pyrimidin-3-yl)-2-propenenitrile was converted into a 5-tetrazolyl group by treatment with NaN3 in the presence of AICI3 in DMF at 100 °C for 2 days. 

The chloro group on the central boron atom of a chloroboron subphthalocyanine may be substituted by a phenyl or hydroxy group. The latter product can be further transformed into an ether.68... 

In the Chemical Abstracts method (also accepted by IUPAC Rule C-912), the naming of monoazo compounds with radicals R derived from two identical parent hydrocarbon hydrides is the same as mentioned above (for an exception see C-912.2). If the azo group links groups that are different when unsubstituted (R-N2-R ), a parent molecule RH is treated as substituted by R -N2- (Rule C-912.4) thus, 1.8 is called 4-(2-hydroxy-l-naphthylazo)benzenesulfonic acid or 4-(2-hydroxy-... 

Substituents replacing the hydrogen atom of an alcoholic hydroxy group of a saccharide or saccharide derivative are denoted as O-substituents. The 0- locant is not repeated for multiple replacements by the same atom or group. Number locants are used as necessary to specify the positions of substituents they are not required for compounds fully substituted by identical groups. Alternative periphrase names for esters, ethers, etc. may be useful for indexing purposes. For cyclic acetals see 2-Carb-28. 

The reactivity of epoxides can be modified by various proximal functionality. For example, 2,3-epoxy sulfides 118 are converted to the corresponding TMS-thiiranium species 119 upon treatment with TMS triflate. This intermediate reacts with O-silyl amides regiospecifically to form l-substituted-3-hydroxy-2-thioethers (e.g., 120). Simple primary amines undergo polyalkylation, but imines can be used as an indirect amine equivalent <96TET3609>. 

In the case of alkenes simply substituted by an electron-withdrawing group (without a y-hydroxy group), the stabilized ylides give first a Michael addition and most often a subsequent prototropic shift resulting in new functionalized ylides (Scheme 8). Then a possible evolution of the resulting ylides can occur to give the final products [40-44]. 

Chiral phosphoryl and sulfinyl groups are known as efficient auxiliaries in asymmetric synthesis. As reported below, their asymmetric induction in the a-posi-tion has been used to prepare chiral non-racemic organophosphorus compounds a-substituted by a sulfur function. Such compounds can also be obtained from their a-hydroxy analogues by OH-4 SR stereoselective transformation. 

Substituted 1-hydroxy cyclohexane-1-carboxyhc acids, which could be prepared from the corresponding cyanohydrins by acid hydrolysis as described above, are important as pharmaceuticals and plant-protective agents. Although the compounds derived from 2- and 3-cyclohexanones have two stereogenic centers, stereoselective syntheses of these interesting products have been published only very recently. " Completely unexpected are the results of HNL-catalyzed additions to 4-substituted cyclohexanones, which do not possess a prochiral center. The (R)-PaHNL-catalyzed addition affords almost exclusively fran -isomers, whereas with (5 )-MeHNL cA-addition is favored (Table 4). ... 

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