Cyclic 1,3-hydroxy

Several examples of the dehydration of acyclic and cyclic hydroxy compounds with CDI, AfN -thiocarbonyldiimidazole, and A -sulfmyldiimidazole, are shown below. 

Aldoximes are normally dehydrated by reaction with dichlorocarbene, produced under soliddiquid two-phase conditions, to yield nitriles in high yield [41, 42], whereas a-hydroxy ketoximes are cleaved with the simultaneous formation of a nitrile and either an aldehyde or ketone (Scheme 7.33). Yields are generally >70% and, in the case of cyclic hydroxy ketoximes, the products are acyclic oxo nitriles [43],... 

In the condensation of diols, halogenated alcohols, amino alcohols, cyclic hydroxy ethers, or other bifunctional hydroxy compounds with carbodiimides, 5-, 6-, and 7-membered 1,3-O-N- or l,3-7V,7V-heterocyclics are obtained [14]. 

The NADP-dependent TBADH was used for the laboratory-scale preparation of several chiral aliphatic and cyclic hydroxy compounds by reduction of the corresponding ketones. For the regeneration of NADPH, this reduction reaction can be coupled with the TBADH catalyzed oxidation of isopropanol. For the reduction of some ketones it was observed that the reaction rate was increased in the presence of the regenerating substrate isopropanol, for instance in the presence of 0.2 v/v isopropanol, the reduction rate of butanone or pentanone was increased 3-4-fold [57], In some cases, the enantiomeric excess of the reduction reaction is not very high, especially when small molecules are converted, but also for compounds such as acetophenone [138]. 

Under these conditions cycloheptene derivative 35 also reacts [15]. After cleavage of the silylether, cyclic hydroxy ketone 37 can be isolated in 95 % yield and 71 % ee. 

Isopropylideneglycerol, a five-membered cyclic hydroxy ketal from acetone and glycerol, is prepared in 90% yield by removing the liberated water by an azeotropic distillation. In another procedure, calcium carbide is added directly to the reaction mixture as a desiccant. Acetaldehyde and benzaldehyde, unlike acetone, react with glycerol to form a mixture of the five- and six-membered cyclic hydroxy acetals. Alkoxy acetals are made by the acetalization of a,/3-olefinic aldehydes in weakly acidic solutions however, the addition of alcohol to the double bond may not go to completion. ... 

Photolysis of 2-j8-hydroxyethylcyclobutanones results in a cyclic hydroxy-carbene, which undergoes an intramolecular insertion into an O — H bond to afford compounds 337 (85AG1073). 

The reactions of acetylene with metal carbonyls can be grouped into two main classes (i) those in which no new C—C bonds are formed, and the acetylene is bonded to the metal atom(s) by /r-bonds, bent a bonds, or by a combination of p and a bonds, and (ii) those in which new C-C bonds are formed by combination of some of the CO with the acetylene to form a cyclic hydroxy-ligand or a lactone ring. 

Recently, advantage was taken of the fact that several Ti-molecular sieves contain both Lewis as well as Bronsted acidic properties. For example, Corma et al showed that Ti-MCM-41 and Ti-Al-Beta are able to catalyze the epoxidation of linalool in the presence of TBHP followed by ring-closure to cyclic hydroxy ethers in a one-pot reaction. Neri et al found that TS-1 catalyzes the epoxidation of styrene, with aqueous H2O2 in MeOH, with in-situ rearrangement to the corresponding aldehyde in 75% yield within 4h. ... 

Fig. 1 Structures of various CD complexes. Toluene fits well into a (3CD cavity, for diphenylamine, two (3CDs form a "capsule. A long-chain fatty acid can take up three or more aCDs. A short-chain fatty acid and diethylether form a stable ternary complex. In the case of prostaglandin E, the otCD accomodates only the aliphatic chain of the unsaturated cyclic hydroxy-fatty acid, but it is enough to convert it into a water-soluble complex. The pCD can accomodate the cyclopentane moiety, but /CD is too wide for this guest. (Wen-this art in color, at www.dekker.com.)...

Procedures for analysing and isolating the various prostaglandins, biologically active cyclic hydroxy-acids, have been published [20, 50]. 

Pentan-2,4-dione reacts with isochalcogensemicarbazides and amidrazones yielding as a rule the corresponding pyrazole (V) as a final product (Scheme 2-2) [78-81]. The reaction proceeds via the formation of either open-chain mono- (I) or bis-(isochalcogensemicarbazones) and/or amidrazones (II), or the cyclic hydroxy-... 

The resistance of cured unsaturated polyesters to chemical attack, i.e., corrosion resistance, has been the subject of many studiesand the subject of several reviews.In general, polyester resins containing cyclic hydroxy compounds, such as hydrogenated bisphenol-A and 1,3- or 1,4-cyclohexanediol or 1,4-cyclohexanedimethanol, have improved chemical resistance.Chemical resistance may also be obtained by employing neopentyl glycol, isophthalic acid trimethyl pentanediol, and propoxylated... 

In 1996, Seebach and co-workers proposed a method based on NMR analysis of the MTPA esters and, more specifically, directed toward the determination of the absolute configuration of hydroxy-sulfonamides. The study was comprised of six cyclic hydroj -sulfonamides, one cyclic hydroxy-ester, and just one acyclic primary alcohol (2-methylbu-tanol) of known configuration. A correlation between the relative configuration of the MTPA esters with the NMR chemical shift of the CF3 group was deduced. Figure 90 shows the structures, chemical shifts, and the empirical model used to explain the correlation. 

Similarly, the two diastereoisomeric cyclic hydroxy esters can be obtained when baker s yeast or R. arrhizus is employed. The successful reduction of these racemic a-substituted (3-keto esters to a single enantiomer is based on the enolization/racemization of the keto esters, which allows a dynamic kinetic resolution. If coupled with the specificity of the enzymes from different microorganisms, this can lead to preparation of compounds of diverse chirality. Thus in the series of the 5- and 6-membered ring compounds (Scheme 18) both the lS,2R-cis- and the lS,2S-trans-hydroxy ester can be obtained by switching from baker s yeast to the biomass from R. arrhizus [97]. Such compounds are highly versatile chiral synthons that have been currently used in the asymmetrical synthesis of biologically active compounds [98]. 

A special group of cyclic hydroxy compounds is constituted by 7-hydroxy lactones [214-217] and cyclic semiacetals [218]. For these sensitive and relatively unstable compounds, the experimental conditions of the enzymatic process seem especially attractive and well suited to obtain efficient and enantioselective resolution of racemic substrates (Scheme 47). 

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. 

XXI XXI, 1st 1935 3103-3241 One Cyclic Nitrogen (continued). Hydroxy compounds Atropine, 27. 

XXV XXV, 1st 1936 3634-3793 Two Cyclic Nitrogens (continued). 1 Hydroxy-carbonyl compounds, 1 1... 

A special problem arises in the preparation of secondary amines. These compounds are highly nucleophilic, and alkylation of an amine with alkyl halides cannot be expected to stop at any specifle stage. Secondary amides, however, can be monoalkylated and lydrolyzed or be reduced to secondary amines (p. 11 If.). In the elegant synthesis of phenyl- phrine an intermediate -hydroxy isocyanate (from a hydrazide and nitrous acid) cyclizes to pve an oxazolidinone which is monomethylated. Treatment with strong acid cleaves the cyclic irethan. 

Diacetates of 1,4-butenediol derivatives are useful for double allylation to give cyclic compounds. l,4-Diacetoxy-2-butene (126) reacts with the cyclohexanone enamine 125 to give bicyclo[4.3.1]decenone (127) and vinylbicy-clo[3.2.1]octanone (128)[85,86]. The reaction of the 3-ketoglutarate 130 with cij-cyclopentene-3,5-diacetate (129) affords the furan derivative 131 [87]. The C- and 0-allylations of ambident lithium [(phenylsulfonyl)methylene]nitronate (132) with 129 give isoxazoline-2-oxide 133, which is converted into c -3-hydroxy-4-cyanocyclopentene (134)[S8]. Similarly, chiral m-3-amino-4-hyd-roxycyclopentene was prepared by the cyclization of yV-tosylcarbamate[89]. 

Propargylic alcohol, after lithiation, reacts with CO2 to generate the lithium carbonate 243, which undergoes oxypalladation. The reaction of allyl chloride yields the cyclic carbonate 244 and PdC. By this reaction hydroxy and allyl groups are introduced into the triple bond to give the o-allyl ketone 245[129]. Also the formation of 248 from the keto alkyne 246 with CO2 via in situ formation of the carbonate 247 is catalyzed by Pd(0)[130]. 

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]. 

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