Modification with diols

Enthalpies of Interaction of Polar Probes with Silicas modified with Diols. Whereas the treatment of silicas with alcohols leads to fixation of alkyl grafts, their modification with diols results in the grafting of hydrocarbon chains still having a... 

Typically such reactions take place between reactive components, such as dibasic acids with diamines to give polyamides, or dibasic acids with diols to form polyesters. This reaction has an important modification in the case of... 

In ditopic hosts 65 the two cationic substructures are linked by a naphthy-lene diether. Schmidtchen observed the formation of 1 1 phosphoester complexes in organic solution with disilylether 65a and in water with diol 65b. The flexible skeleton enables the hosts to wrap around phosphate forming two pairs of hydrogen bonds with perpendicular main planes as schemed in formula 66 for the 5 -TMP complex [98]. Similarly, the complexation of AMP derivatives, NAD, and other phosphates by the related host 16 (Sect. 2) and its desilylated modification have been reported recently [99]. 

Guo B, Anzai J, Osa T. Modification of a glassy carbon electrode with diols for the suppression of electrode fouling in biological fluids. Chemical and Pharmaceutical Bulletin (Tokyo) 1996, 44, 860-862. 

Modifications of alkoxysilanes with diols or polyols such as ethylene glycol, glycerol, etc. have been well known since the middle of the last century however, their application was hampered by their hydrolytic instability [7, 8]. Only in recent years is interest in this type of glycol-modified silanes increasing again because of some obvious advantages ... 

The post-modification with propylene oxide gives the best catalytic results, both with Sil-GP-tacn and MCM-GP-tacn. For the latter system, methanol seems a superior solvent in comparison with acetone and acetonitrile. The epoxide selectivity in reaction 7 is limited, but this is due to secondary reactions of initially formed epoxide to phenylacetaldehyde and the diol. When these secondary products are taken into account, the selectivity for the epoxide and its derived products increases to 76 %. 

Marshall, C.J., Vousden, K.H., and Phillips, D.H. (1984) Activation of c-Ha-ras-1 proto-oncogene by in vitro chemical modification with a chemical carcinogen, benzo[o]pyrene diol-epox-ide. Nature, 310, 585-589. 

Silica gel may also be modified with hydrophilic groups that are attached using short-chain nonpolar spacers. Hydrophilic modifications with polar groups include amino, cyano, and diol functionalities. Amino-SG offers weakly basic ion-exchange properties diol-SG considerably less affinity for water when compared with unmodified SG-60. These HPTLC materials offer increased selectivity for complex separations of biomolecules and drugs. 

Typically such reactions take place between reactive components, such as dibasic acids with diamines to give polyamides, or dibasic acids with diols to form polyesters. This reaction has an important modification in the case of nylon 6,6 [poly(hexa-methylene adipamide)], where the initial product of reaction between hexamethylenediamine and adipic acid is a salt, which can be recrystallised readily in order to obtain the high-purity intermediate essential for conversion to high molar mass product. The condensation part of the reaction in this case is brought about by heating the intermediate salt. 

As mentioned earlier, CABE prepolymers are synthesized via a simple thermal polycondensation process by reacting citric acid with diol monomers (Figure 16.2 and Table 16.1). Citric acid confers CABEs with pendent functionality for postmodification or concurrent modification and cross-linking. While the elasticity of CABEs mostly depends on the chain length of the diol used, if... 

Several new chiral modifications of lithium aluminium hydride have been reported, including those formed by reaction with chiral secondary benzylamines (14), with diols such as (15) derived from D-mannitol, or with terpenic glycols such as (16). These complexes reduce phenyl alkyl ketones to optically active phenyl carbinols, and enantiomeric excesses of up to 50% have been observed in the case of reagents derived from (14). However, in the diol complexes, believed to have structures of the type shown in (17), lower chiral selectivity is observed, e.g. up to ca. 12% in the case of (15), or up to an optical yield of 30% with an ethanol-modified complex of (16). Better results have been reported with the chiral diamine complex (18), derived originally from L-proline, which reduces acetophenone in 92% optical yield. Asymmetric induction with reagents in this class (i.e. derivatives of lithium aluminium hydride) is usually low in the reduction of aliphatic ketones, but a complex of UAIH4 and the amino-alcohol (19) has been shown to reduce... 

Properties of DGEBA (58) can be modified by use of alkyl diols for ouring agents however, the effect on mechanical xopeities is not as desirable as modification with thermoplastics. 

Cadiz and co-workers [46] prepared telechelic polyester diols through two subsequent thiol-ene reactions. That is, a step growth polymerisation using allyl-lO-undecenoate and 3,6-dioxa-l,8-octanedithiol, followed by end-group post-polymerisation modification with 2-mercaptoethanol. Telechelics based on divinyl monomers are interesting materials with potential applications in the tailoring of polymer structures and properties. 

Gogeva, T. and S. Fakirov, Poly(ether/ester)s based on poly(tetramethylene terephthalate) and poly(ethylene glycol), 4. Modification with 2-butyne-1,4-diol. Die Makromolekulare Chemie, 191(10) p. 2355.1990. 

Fig. 14. DSC curves of the polyurethane hard segment model compounds Diol-n (Fig. 14a) and Urethane-n (Fig. 14b) heating rate 20 C/min dashed curve is the crystalline modification of Diol-1 with the contracted conformation.

Useful for modification of solubility properties of peptide derivatives The reactive hydroxyl functions of the boronic acid (pKg -9) can be masked by rapid, reversible reactions with diols. 

Stmctural and chemical modification of urethane containing polymer matri-ces with macrocycles - calixarenes having reactive hydrazide groups have been carried out and stmcture, physico chemical and sensor properties of polyure-thanesemicarbazides (PUS) synthesised have been studied. The polymers obtained (on the base of polypropylene glycol MM 1000 and polysiloxane diol MM 860, hexamethylene diisocyanate and calixarene dihydrazide) are identified by IR-spectroscopy, size exclusion chromatography (SEC), DSC, WAXS and SAXS methods. 

In further modifications of these norprogestins, reaction of norethindrone with acetic anhydride in the presence of p-toluene-sulfonic acid, followed by hydrolysis of the first-formed enol acetate, affords norethindrone acetate (41). This in turn affords, on reaction with excess cyclopentanol in the presence of phosphorus pentoxide, the 3-cyclopentyl enol ether (42) the progestational component of Riglovic . Reduction of norethindrone affords the 3,17-diol. The 33-hydroxy compound is the desired product since reactions at 3 do not show nearly the stereoselectivity of those at 17 by virtue of the relative lack of stereo-directing proximate substituents, the formation of the desired isomer is engendered by use of a bulky reducing agent, lithium aluminum-tri-t-butoxide. Acetylation of the 33,173-diol iffords ethynodiol diacetate, one of the most potent oral proves tins (44). ... 

Henderson and Sutherland have prepared a hydrocarbon synthetically which is possibly a modification of terpinene. They reduced thymo-hydroquinone, thus obtaining menthane-2-5-diol, which was heated for half an hour with twice its weight of sulphate of potash under a reflux condenser, and so yielded a terpene boiling at 179°, of specific gravity about 0 840 and refractive index 1-4779. 

Chiral modification of diorganomagnesium compounds with the dilithium salt oi (S)-l,l -bi-naphthalene-2,2 -diol gave reagents with the empirical formula 30. Good to excellent enantiose-lectivities were observed in addition reactions of aliphatic and aromatic reagents to aromatic aldehydes30,31, however, the selectivities were not satisfactory with allylic, vinylic and acetylenic reagents. 

Addition of the analogous methyltitanium reagent to bcnzaldchydc afforded the addition product with only 59% ee34. Use of the methyltitanium reagent obtained via chiral modification by the tartaric acid derived diol 43, did not lead to an improvement of the enantioselectivity42. 

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