2.4- Dimethyl-2,4-pentanediol

Inorganic arsenic complexes based on oxygen ligands is scarce. Simple esters of arsenic acid, As(0)(0R)3 (R = Me, Ft, n-Pr, n-Bu, CeHn) have tetragonal structures. Reaction of the diol ligand 2,4-dimethyl-2,4-pentanediol with AsCfr affords an arsenic chloride complex in which the As atom is part of a six-membered ring (37). ... 

Prepared from benzonitrile, 2,4-dimethyl-2,4-pentanediol and 96% sulfuric acid [E.-J. Tillmanns andJ. J. Ritter, J. Org., 22,839 (1957)]... 

Due to the differences in the values relative to any one system, conclusions cannot easily be drawn from the activation parameters listed in Table 3. However, an analysis of the results relative to 1,2-ethanediol, 2,2-dimethyl-l,3-propanediol, 1,5-pentanediol, 1,10-decanediol and diethylene glycol shows that a slight difference can be observed between aromatic and aliphatic acids the activations enthalpies and entropies are in the ranges 70, 100 kJ mol"1 and -SO, -130 J K"1 mol-1 for aromatic acids, and in the ranges 50, 70 kJ mol"1 and -200, -100 J K"1 mol-1 for the aliphatic acids. 

As depicted in Fig. 6, syntheses of enantiomerically pure 116 and 117 have been carried out [236]. Lipase AK-catalysed asymmetric acetylation of meso-2,4-dimethyl-1,5-pentanediol A yielded (2R,4S)-5-acetoxy-2,4-dimethylpen-tanol B. Protection of the free hydroxy group as the terf-butyldimethylsilyl (TBS) ether, saponification of the acetate, and oxidation furnished the aldehyde C. Reaction of C with ethylmagnesium bromide gave a diastereomeric mixture of the corresponding secondary alcohols which could be resolved by asym-... 

ANTI-SELECTIVE BORON-MEDIATED ASYMMETRIC ALDOL REACTION OF CARBOXYLIC ESTERS SYNTHESIS OF (2S, 3R)-2,4-DIMETHYL-1,3-PENTANEDIOL... 

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. 

Diprotonated 2,4-pentanediol 10 loses water and rearranges to form 1,3-dimethyl allyl cation [Eq. (4.6)]. Diprotonated 2,5-hexanediol 11, above — 30°C, rearranges to a mixture of protonated cis- and tra .v-2,5-dimethyltetrahydrofurans [Eq. (4.7)]. This would seem to indicate that there is a significant amount of the monoprotonated form present or that the carbocation formed can easily lose a proton before ring formation occurs. 

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