Organic synthesis 1,3-diols

There are ample evidences which suggest that a cyclic periodate ester is the intermediate 148). Cyclobutane-1,2-diols can also be cleaved oxidatively and this aspect has been used in organic synthesis. Thus, photocycloaddition of l,2-bis(tri-methylsiloxy)cyclobutene to (—)piperitone (381) gave the photoadduct (438). Desilyla-... 

The conventional thinking in organic synthesis indicates that primary hydroxyls are more reactive than secondary hydroxyls [96], Under this assumption, the glycosylation of triol 157 to furnish diol 158 by exclusive glycosylation at the... 

The 1,3,2-dioxastannolanes are important in organic synthesis because they can readily be derived from dialkyltin oxide and 1,2-diols, as in carbohydrates the reaction can be carried out in toluene in a few minutes under microwave irradiation.387 The dioxastannolanes can then be subjected to regioselective reaction with an electrophile such as an acyl chloride (Equation (140)) or sulfonyl chloride, or an isocyanate. The acylation or sulfonation can be carried out with catalytic amounts of the dialkyltin oxide, including the recoverable (C6F13CH2CH2)2Sn0.388... 

The catalytic asymmetric epoxidation of a,/i-unsaturated carbonyl compounds is one of the synthetically useful reactions in organic synthesis.The resulting chiral epoxides are easily converted to various useful chiral compounds. We developed a new yttrium-(5)-6,6 -[oxybis(ethylene)dioxy]biphenyl-2,2 -diol (1) (Figure 6.10)... 

For reviews, see Starks Liotta, Ref. 404, pp. 128-138 Weber Gokel Phase Transfer Catalysis in Organic Synthesis, Ref. 404, pp. 73-84. For the use of phase transfer catalysis to convert, selectively, one OFI group of a diol or triol to an ether, see de la Zerda Barak Sasson Tetrahedron 1989, 45, 1533. 

Organotin compounds are key intermediates in organic synthesis,6 as they are useful in a variety of carbon-carbon bond-forming reactions. For example, lithium and cuprate reagents may be formed from organostannane precursors. The tin compounds are also used in catalytic reactions of diols (or triols) and diisocyanates for the manufacture of polyurethane. Because... 

Prochiral diols -enzymatic acylation [ENZYMES IN ORGANIC SYNTHESIS] (Vol 9)... 

Hydrogen peroxide and alkyl hydroperoxides are important oxidants in organic synthesis, but they usually need to be activated by catalysts such as tungsten, molybdenum, and titanium oxides. Heteropoly compounds are good catalysts for oxygenation of olefins or paraffins and oxidative cleavage of vic-diols. 

Details for the large-scale synthesis of (R,R) 1,2-diphenyl-1,2-ethanediol by using the DHQD-CLB/NMO variation of catalytic AD have been published [47]. Under these conditions the crude diol is produced with 90% ee and upon crystallization, essentially enantiomerically pure diol is obtained in 75% yield. Subsequent improvements in the catalytic AD process now allow this dihydroxylation to be achieved with >99.8% ee (entry 20, Column 9) however, the Organic Synthesis procedure [47] is still an excellent choice for preparing large amounts of the... 

Microbially Produced Functionalized Cyclohexadiene-trans-diols as a New Class of Chiral Building Blocks in Organic Synthesis On the Way to Green and Combinatorial Chemistry... 

To develop new methods for organic synthesis, Woerpel and coworkers exploited the inherent reactivity of di -fc/ f-butylsilacyclopropanes to create new carbon-carbon bonds in a stereoselective fashion (Scheme 7.7).62 They discovered that transition metal salts catalyze the insertion of carbonyl compounds into the strained carbon-silicon bond to form oxasilacyclopentanes. The regioselectivity of insertion could be controlled by the identity of the catalyst. Copper promoted the insertion of croto-naldehyde into the more substituted C-Si bond of 52 to afford oxasilacyclopentane 53,63 whereas zinc catalyzed the insertion of butyraldehyde into the less substituted bond of 52 to provide the complementary product, 54.64 Oxasilacyclopentanes (e.g., 55) could be transformed into useful synthetic intermediates through oxidation of the C-Si bond,65 66 which provided diol 56 with three contiguous stereocenters. 

Apart from the diols examined so far there are other bis-O nucleophiles that also react with carbonyl compounds following the mechanisms discussed, as illustrated by Figure 9.21. The result is acetal analogs such as the compounds D (from hydroxy carboxylic acid A), E (from enol carboxylic acid wo-B) or F ( Meldrum s acid from malonic acid). Each of these acetal analogs is used as a reagent in organic synthesis. 

The body oxidizes the alkene components of drugs and other substances to epoxides, which are then hydrolyzed to diols by an epoxide hydrolase enzyme. The more reactive epoxides are rapidly converted to water-soluble diols and eliminated in the urine. Epoxide hydrolase enzymes are sometimes used in organic synthesis to produce chiral diols. 

Instead of starting with racemic starting material it is also possible to use symmetric substrates [25]. The hydrolase selectively catalyses the hydrolysis of just one of the two esters, amides or nitriles, generating an enantiopure product in 100% yield (Scheme 6.7). No recycling is necessary, nor need catalysts be combined, as in the dynamic kinetic resolutions, and no follow-up steps are required, as in the kinetic resolutions plus inversion sequences. Consequently this approach is popular in organic synthesis. Moreover, symmetric diols, diamines and (activated) diacids can be converted selectively into chiral mono-esters and mono-amides if the reaction is performed in dry organic solvents. This application of the reversed hydrolysis reaction expands the scope of this approach even further [22, 24, 27]. 

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