Groups hydroxy

There also exist natural fatty acids with four or more double bonds, fatty acids with hydroxy groups in the molecule, and certain cyclic fatty acids. 

The nitrochlorobenzenes are valuable dyestufTs intermediates. The presence of the nitro-groups makes the chlorine atom very reactive and easily replaceable. Treatment with ammonia or dilute alkalis substitutes an amino- or hydroxy-group for the chlorine atom and gives a series of nilroanilines and nilrophenols. 

The synthesis of vitamin Dj from a sensitive dienone was another etu-ly success of phosphorus ylide synthesis (H.H. Inhoffen, 1958 A). This Wittig reaction could be carried out without any isomerization of the diene. An excess of the ylide was needed presumably because the alkoxides formed from the hydroxy group in the educt removed some of the ylide. 

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.). 

If a bromomethyl- or vinyl-substituted cyclopropane carbon atom bears a hydroxy group, the homoallyiic rearrangement leads preferentially to cyclobutanone derivatives (J. Sa-laun, 1974). Addition of amines to cydopropanone (N. J. Turro, 1966) yields S-lactams after successive treatment with tert-butyl hypochlorite and silver(I) salts (H.H. Wasserman, 1975). For intramolecular cyclopropane formation see section 1.16. 

The first practical method for asymmetric epoxidation of primary and secondary allylic alcohols was developed by K.B. Sharpless in 1980 (T. Katsuki, 1980 K.B. Sharpless, 1983 A, B, 1986 see also D. Hoppe, 1982). Tartaric esters, e.g., DET and DIPT" ( = diethyl and diisopropyl ( + )- or (— )-tartrates), are applied as chiral auxiliaries, titanium tetrakis(2-pro-panolate) as a catalyst and tert-butyl hydroperoxide (= TBHP, Bu OOH) as the oxidant. If the reaction mixture is kept absolutely dry, catalytic amounts of the dialkyl tartrate-titanium(IV) complex are suflicient, which largely facilitates work-up procedures (Y. Gao, 1987). Depending on the tartrate enantiomer used, either one of the 2,3-epoxy alcohols may be obtained with high enantioselectivity. The titanium probably binds to the diol grouping of one tartrate molecule and to the hydroxy groups of the bulky hydroperoxide and of the allylic alcohol... 

Six protective groups for alcohols, which may be removed successively and selectively, have been listed by E.J. Corey (1972B). A hypothetical hexahydroxy compound with hydroxy groups 1 to 6 protected as (1) acetate, (2) 2,2,2-trichloroethyl carbonate, (3) benzyl ether, (4) dimethyl-t-butylsilyl ether, (5) 2-tetrahydropyranyl ether, and (6) methyl ether may be unmasked in that order by the reagents (1) KjCO, or NH, in CHjOH, (2) Zn in CHjOH or AcOH, (3) over Pd, (4) F", (5) wet acetic acid, and (6) BBrj. The groups may also be exposed to the same reagents in the order A 5, 2, 1, 3, 6. The (4-methoxyphenyl)methyl group (=MPM = p-methoxybenzyl, PMB) can be oxidized to a benzaldehyde derivative and thereby be removed at room temperature under neutral conditions (Y- Oikawa, 1982 R. Johansson, 1984 T. Fukuyama, 1985). 

The benzylidene derivative above is used, if both hydroxyl groups on C-2 and C-3 are needed in synthesis. This r/vzns-2,3-diol can be converted to the sterically more hindered a-cpoxide by tosylation of both hydroxy groups and subsequent treatment with base (N.R. Williams, 1970 J.G. Buchanan, 1976). An oxide anion is formed and displaces the sulfonyloxy group by a rearside attack. The oxirane may then be re-opened with nucleophiles, e.g. methyl lithium, and the less hindered carbon atom will react selectively. In the following sequence starting with an a-glucoside only the 2-methyl-2-deoxyaltrose is obtained (S. Hanessian, 1977). 

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trilluoride ( DAST M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

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... 

When the 2-hydroxy group of a monosaccharide reacts with (diethylamino)sulfur trifluoride (DAST), quantitative and stereoselective rearrangements are observed (K.C Nico-laou, 1986). This reaction may simultaneously introduce fluorine to C-1 and a new oxygen, sulfur, or nitrogen residue to C-2 with inversion of configuration. 

Aryl, heteroaryl, and alkenyl cyanides are prepared by the reaction of halides[656-658] or triflates[659,660] with KCN or LiCN in DMF, HMPA, and THF. Addition of crown ethers[661] and alumina[662] promotes efficient aryl and alkenyl cyanation. lodobenzene is converted into benzonitrile (794) by the reaction of trimethylsiiyl cyanide in EtiN as a solvent. No reaction takes place with aryl bromides and chlorides[663]. The reaction was employed in an estradiol synthesis. The 3-hydroxy group in 796 was derived from the iodide 795 by converting it into a cyano group[664]. 

The reaction of vinyloxiranes with malonate proceeds regio- and stereose-lectively. The reaction has been utilized for the introduction of a 15-hydroxy group in a steroid related to oogoniol (265)(156]. The oxirane 264 is the J-form and the attack of Pd(0) takes place from the o-side by inversion. Then the nucleophile comes from the /i-side. Thus overall reaction is sT -StM2 type, in the intramolecular reaction, the stereochemical information is transmitted to the newly formed stereogenic center. Thus the formation of the six-membered ring lactone 267 from 266 proceeded with overall retention of the stereochemistry, and was employed to control the stereochemistry of C-15 in the prostaglandin 268[157]. The method has also been employed to create the butenolide... 

As a further application of the reaction, the conversion of an endocyclic double bond to an c.xo-methylene is possible[382]. The epoxidation of an cWo-alkene followed by diethylaluminum amide-mediated isomerization affords the allylic alcohol 583 with an exo double bond[383]. The hydroxy group is eliminated selectively by Pd-catalyzed hydrogenolysis after converting it into allylic formate, yielding the c.ro-methylene compound 584. The conversion of carvone (585) into l,3-disiloxy-4-methylenecyclohexane (586) is an example[382]. 

The Pd-catalyzed hydrogenolysis of vinyloxiranes with formate affords homoallyl alcohols, rather than allylic alcohols regioselectively. The reaction is stereospecific and proceeds by inversion of the stereochemistry of the C—O bond[394,395]. The stereochemistry of the products is controlled by the geometry of the alkene group in vinyloxiranes. The stereoselective formation of stereoisomers of the syn hydroxy group in 630 and the ami in 632 from the ( )-epoxide 629 and the (Z)-epoxide 631 respectively is an example. 

The telomer 145 of nitroethane was used for the synthesis of recifeiolide (148)[121], The nitro group was converted into a hydroxy group via the ketone and the terminal double bond was converted into iodide to give 146. The ester 147 of phenythioacetic acid was prepared and its intramolecular alkylation afforded the 12-membered lactone, which was converted into recifeiolide (148),... 

Addition of a hydroxy group to alkynes to form enol ethers is possible with Pd(II). Enol ether formation and its hydrolysis mean the hydration of alkynes to ketones. The 5-hydroxyalkyne 249 was converted into the cyclic enol ether 250[124], Stereoselective enol ether formation was applied to the synthesis of prostacyclin[131]. Treatment of the 4-alkynol 251 with a stoichiometric amount of PdCl2, followed by hydrogenolysis with formic acid, gives the cyclic enol ether 253. Alkoxypalladation to give 252 is trans addition, because the Z E ratio of the alkene 253 was 33 1. 

The cyclic enol ether 255 from the functionalized 3-alkynoI 254 was converted into the furans 256 by the reaction of allyl chloride, and 257 by elimination of MeOH[132], The alkynes 258 and 260, which have two hydroxy groups at suitable positions, are converted into the cyclic acetals 259 and 261. Carcogran and frontalin have been prepared by this reaction[124]. 

Butyrolactones are prepared by intramolecular reaction of haloallylic 2-alkynoates. The a-chloromethylenebutyrolactone 301 is prepared by the intramolecular reaction of300[150,151]. 4 -Hydroxy-2 -alkenyl 2-alkynoates can be used instead of haloallylic 2-alkynoates, and in this reaction, Pd(II) is regenerated by elimination of the hydroxy group[152]. As a related reaction, the q-(chloromethylene)-7-butyrolactone 304 is obtained from the cinnamyl 2-alkynoate 302 in the presence of LiCl and CuCbflSS]. Isohinokinin (305) has been synthesized by this reaction[l 54]. The reaction is explained by chloro-palladation of the triple bond, followed by intramolecular alkene insertion to generate the alkylpalladium chloride 303. Then PdCb is regenerated by attack of CuCb on the alkylpalladium bond as a key step in the catalytic reaction. 

When unsubstituted, C-5 reacts with electrophilic reagents. Thus phosphorus pentachloride chlorinates the ring (36, 235). A hydroxy group in the 2-position activates the ring towards this reaction. 4-Methylthiazole does not react with bromine in chloroform (201, 236), whereas under the same conditions the 2-hydroxy analog reacts (55. 237-239. 557). Activation of C-5 works also for sulfonation (201. 236), nitration (201. 236. 237), Friede 1-Crafts reactions (201, 236, 237, 240-242), and acylation (243). However, iodination fails (201. 236). and the Gatterman or Reimer-Tieman reactions yield only small amounts of 4-methyl-5-carboxy-A-4-thiazoline-2-one. Recent kinetic investigations show that 2-thiazolones are nitrated via a free base mechanism. A 2-oxo substituent increases the rate of nitration at the 5-position by a factor of 9 log... 

Direct sulfonation of thiazole, as well as of 2-substituted thiazoles, leads mostly to substitution m the 5-position (330-332). 4-Thiazole sulfonic acid has been prepared through direct sulfonation of 2.5-dibromothiazole with subsequent Rane% Ni reduction (330). Sulfonation of 2.5-dimethyl- and 2-piperidyl-5-methylthiazoles affords the corresponding 4-sulfonic acids as barium salts (247). The 2-hydroxy group facilitates the sulfonation (201. 236). When the 4- and 5-positions are occupied direct sulfonation can occur in the 2-position. 5-hydroxyethyl-4-methyl-2-thiazole sulfonic acid has been prepared in this manner (7). 

Rayon. Viscose rayon is obtained by reacting the hydroxy groups of cellulose with carbon disulfide in the presence of alkali to give xanthates. When this solution is poured (spun) into an acid medium, the reaction is reversed and the cellulose is regenerated (coagulated). 

Calixarenes (from the Latin ca/ x) may be understood as artificial receptor analogues of the natural cyclodextrins (96,97). In its prototypical form they feature a macrocycHc metacyclophane framework bearing protonizable hydroxy groups made from condensation of -substituted phenols with formaldehyde (Fig. 15b). Dependent on the ring size, benzene derivatives are the substrates most commonly included into the calix cavity (98), but other interesting substrates such as C q have also been accommodated (Fig. 8c) (45). 

Xanthene dyes are those containing the xanthylhim [261-23-4] (la) or diben2o-y-pryan nucleus [92-83-1] (xanthene) (lb) as the chromophore with amino or hydroxy groups meta to the oxygen as the usual auxochromes. They are... 

The most important industrial use of pentaerythritol is in a wide variety of paints, coatings, and varnishes, where the cross-linking capabiUty of the four hydroxy groups is critical. Alkyd resins (qv) are produced by reaction of pentaerythritol with organic acids such as phthaUc acid or maleic acid and natural oil species. 

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