Diols and polyols

Phosphorus-Containing Diols and Polyols. The commercial development of several phosphoms-contaiuing diols occurred in response to the need to flame retard rigid urethane foam insulation used in transportation and constmction. There are a large number of references to phosphoms polyols (111) but only a few of these have been used commercially. 

Titanium chelates are formed from tetraalkyl titanates or haUdes and bi- or polydentate ligands. One of the functional groups is usually alcohoHc or enoHc hydroxyl, which interchanges with an alkoxy group, RO, on titanium to Hberate ROH. If the second function is hydroxyl or carboxyl, it may react similarly. Diols and polyols, a-hydroxycarboxyflc acids and oxaUc acid are all examples of this type. P-Keto esters, P-diketones, and alkanolamines are also excellent chelating ligands for titanium. 

Phenylboronic acid in particular has proved invaluable, since its complexes with cis-diols and -polyols have formed the basis... 

Smaller aldehydes form cyclic acetal-type oligomers readily in aqueous conditions.60 Diols and polyols also form cyclic acetals with various aldehydes readily in water, which has been applied in the extraction of polyhydroxy compounds from dilute aqueous solutions.61 E in water was found to be an efficient catalyst for chemoselective protection of aliphatic and aromatic aldehydes with HSCH2CH2OH to give 1,3-oxathiolane acetals under mild conditions (Eq. 5.7).62... 

Many diols and polyols like 1, 4-butanediol and hydroxy-terminated polyesters or polyethers or polyesteramides are used for reaction with diisocyanates commercially. 

Abstract This is one of the most important classes of oxidation effected by Ru complexes, particnlarly by RnO, [RuO ] , [RnO ] and RuCljCPPhj), though in fact most Ru oxidants effect these transformations. The chapter covers oxidation of primary alcohols to aldehydes (section 2.1), and to carboxylic acids (2.2), and of secondary alcohols to ketones (2.3). Oxidation of primary and secondary alcohol functionalities in carbohydrates (sugars) is dealt with in section 2.4, then oxidation of diols and polyols to lactones and acids (2.5). Finally there is a short section on miscellaneous alcohol oxidations in section 2.6. 

Molecules with Two or More Functional Nonchromophoric Groups 4.4.2.4.I. Derivatives of Cyclic Diols and Polyols... 

Due to the complexity of conformational equilibria, the application of the dibenzoate chirality rule to determination of the absolute configuration of acyclic diols and polyols requires cautious evaluation of the CD data. For example, (0,0)-dibenzoyl derivatives of diesters and N.N.N ,AT-tetraalkyldiamides of (/t,f )-tartaric acid give exciton Cotton effects of opposite sign due to the preference of diesters for a planar and tetraalkyldiamides for a gauche conformation of the carbon chain176. 

Diols and polyols can participate in equilibria with boric acid in aqueous solution. The stability of polyolborates is determined by the number of OH groups in cis positions. Complexes with polyols are more stable than with diols, and 1,2-diol complexes are more stable than their 1,3-diol counterparts (Table 10) since the resulting five-membered chelate ring is unstrained.75120 In the case of 1,3,5-triols stable cage-like structures (5) and (6) are favored. Open-chain or five-membered cyclic polyols form more stable chelate complexes than their six-membered counterparts.120 Thus, chelates from alditols and ketohexoses are more stable than the corresponding aldose chelates (Table 10). Many polyols allow quantitative titrimetric determination of boric acid. Of these, mannitol remains the most widely used reagent on the basis of availability, cost and ease of handling.75... 

O-protected cyclic or acyclic carbon frameworks. The choice of acetals or ethers as derivatives allows a systematic manipulation of diols and polyols. Kinetic control and a lesser affinity for protonation on sulfur compared with oxygen allows the transformation of cyclic hemiacetals into acyclic dialkyl dithioacetals. Acetal, ether, and dithioacetal derivatives are some of the pivotal intermediates needed to explore various applications of carbohydrates in synthesis. 

Dihalides with two different halogens Boron tribromide, 43 Diols and polyols... 

In situ amine-impregnated silica gel Amine- or amide-bonded phases Diol- and polyol-bonded silica gel Anion exchangers Cation exchangers... 

The use of performed dibutyltin dimethoxide is advantageous12-14 reactions of diols are complete in 5-15 min in benzene at reflux. This technique avoids the problems with working in methanol just mentioned, and gives better yields. The preparation of stannylene acetals is also accelerated by microwave irradiation,15 and selective reactions can be performed, albeit in low yields, on some diols and polyols by microwave irradiation in the presence of a catalytic amount of dibutyltin oxide.16,17... 

Acetals reveal virtually unlimited stability to basic conditions but they are quite fragile towards acid — a property that derives from participation of a lone pair on the adjacent oxygen atom in the cleavage of a protonated intermediate as depicted in Scheme 1.6. Moreover, there is a wide range of acid lability depending on the structure of the acetal — a subject that was aired previously in Chapter 2. In this chapter our discussion of acetals will only embrace matters pertinent to the protection of diols and polyols. 

These two reactions were elegantly combined in the deoxydehydration of diols and polyols to alkenes and aUylic alcohols catalyzed by ReCp Os/PPhs, which provides a useful means of reducing oxygen-rich organics like carbohydrates. ... 

Diols and polyols have also been used effectively as proton sources in hydroesterification. For example, ethylene glycol, 1-octene, Co2(CO)g, and in the molar ratio... 

In a similar fashion, diols and polyols can be transformed selectively to important chemicals, e. g. carbonyl compounds, dienes and cyclic ethers. Numerous reviews give adequate treatment of the dehydration both of monohydric alcohols [1-11] and of diols and polyols [12-14]. 

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