1.4- Diols 2,5-dimethyl-2,5-hexanediol

Lactones are the main products in the reaction of carbon monoxide and diols with structures that favor lactone formation. Thus, 2,5-dimethyl-hexanediol-2,5 reacts to give the corresponding Cg-lactone [652], whereas e. g. butanediol-1,3 reacts to give tiglic acid in about 10% yield [653]. 

Reduction. Hydrogenation of dimethyl adipate over Raney-promoted copper chromite at 200°C and 10 MPa produces 1,6-hexanediol [629-11-8], an important chemical intermediate (32). Promoted cobalt catalysts (33) and nickel catalysts (34) are examples of other patented processes for this reaction. An eadier process, which is no longer in use, for the manufacture of the 1,6-hexanediamine from adipic acid involved hydrogenation of the acid (as its ester) to the diol, followed by ammonolysis to the diamine (35). 

Diols from Lithium P-Lithioalkoxides Generated by the Reductive Lithiation of Epoxides 2,5-Dimethyl-2,4-hexanediol. 

B. Mudryk and T. Cohen 173 1,3-DIOLS FROM LITHIUM p-LITHIOALKOXIDES GENERATED BY THE REDUCTIVE LITHIATION OF EPOXIDES 2,5-DIMETHYL-2,4-HEXANEDIOL... 

If a diastereomeric mixture of (S,S)-2,5-dimethyl-3.4-hexanediol esters 2 and 3 reacts with methylmagnesium bromide, the result is kinetic resolution, as verified for R1 = Bn. The diastereomeric mixture was prepared from the racemic ethylene glycol a-chloro boronic ester via transesterification with chiral diol. The products isolated were (S,S)-2,5-dimethyl-3,4-hexanediol [(/ )-2-phcnyl-l-methylethyl]boronate, diastereomeric ratio >95 5 as indicated by the rotation of the (/ )- -phenyl-2-propanol derived by deboronation with hydrogen peroxide, and (S,S)-2,5-dimethyl-3.4-hexanediol methylboronate. Phenylacetaldehyde was identified by 1H NMR4. 

This reaction was applied to a mixture of diastereoisomeric diols [113], For instance, a,cx -dimethyl-l,4-benzenedimethanol was treated with Ru complex 30 (S/C=25), Novozyme 435, and 4-chlorophenyl acetate (3 equiv) in toluene at 70 °C to give the R,R diacetate in >99% ee and the meso isomer (R,R meso=98 2) in 77% yield (Scheme 40). Reaction of 1,3-pentanediol and 1,4-hexanediol gave the corresponding R,R diacetate in >99% ee, while the R,R to meso ratio was lower than that of the aromatic diacetate. Nitrogen-containing substrates also gave the desired products in optically pure form. 

Other procedures to obtain the polymer include the use of terephthalic acid esterified to its dimethyl ester, which by a transesterification reaction with ethylene glycol generates the polymer. In addition to ethyleneglycol, other diols can be used in the esterification readion, such as 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, etc. 

Aromatic polyesters were enzymatically synthesized under mild reaction conditions. Divinyl esters of isophthalic acid, terephthalic acid, and p-phen-ylene diacetic acid were polymerized with glycols by lipase CA catalyst to give polyesters containing an aromatic moiety in the main chain.208 In the lipase-catalyzed polymerization of dimethyl isophthalate and 1,6-hexanediol in toluene with nitrogen bubbling, a mixture of linear and cyclic polymers was formed.209 High molecular weight aromatic polyester (Mw 5.5 x 104) was synthesized by the lipase CA-catalyzed polymerization of isophthalic acid and 1,6-hexanediol under vacuum.210 Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters.211... 

Aliphatic polycarbonates (polyesters of carbonic acid) are obtained by the transesterification reaction of dialkyl carbonates (for example dimethyl carbonate) with aliphatic diols. A typical example is the polycondensation of dimethyl carbonate with 1,6 hexanediol (reaction 8.3) [4-8] ... 

Conversion of dihydroxy compounds to diamines requires the repetition of all reaction steps (dehydrogenation, addition, elimination, hydrogenation). Selectivity is much higher when diols are transferred only to amino alcohols or amino alcohols to diamines. This difference is exemplified by the reaction of 1,6-hexanediol with di-methylamine over CU/AI2O3 [25]. Over 90% selectivity for the intermediate N,N-dimethyl-6-amino-l-hexanol was achieved at 180 °C in a continuous fixed-bed reactor. To complete the amination of the second OH group the reactor temperature had to be raised to 230 °C and the highest selectivity for diamine was only 65 %. 

AI3-20686 Dimethylhexanediol 2,6-Dimethyl-2,5-hexanediol 2,5-Dimethylhexane-2,5-diol EINECS 203-731-5 2,5-Hexanediol, 2,5-dimethyl- HSDB 5395 NSC 5595 1,1,4,4-Tetramethyl-1,4-butanediol. Prisms mp = 92° bp = 214° d = 0.898 soluble in H2O. very soluble in EtOH, CeHe, CHCI3. 

Hexanediol heated with a Co-kieselguhr catalyst until a vigorous H2-evolu-tion starts, product-water mixture distilled off while more diol is added drop-wise 2,5-dimethyl-2,3-dihydrofuran. Y 76%. F. e. s. P. Dimroth and H. Pase-dach, Ang. Gh. 72, 865 (1960). 

The acid-catalyzed cyclodehydration of ( )- and meso-2,5-hexanediol has been shown to proceed with inversion of configuration in most cases, affording cis- and rra/if-2,S-dimethyltetrahydrofuran, respectively. However, various extents of racemization are observed in the actions of certain Lewis acids and H2S04. The stereospecific cyclization of diols to tetrahydrofurans occurs if phenylthio participation is involved. The reactions of 2-phenylthio-l,4-diols such as (118) with dimethyl sulfate afford (119) with net retention of configuration, whereas acid-catalyzed cyclizations of 4-phenylthio-l,3-diols such as (120) take place with PhS migration and hence inversion at both the migration origin and terminus (Scheme 50). °°... 

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