1.2- Pentanediol

Shimizu, S. Yamada, H. Hata, H. Morishita, T Akutsu, S. Kawamura, M. Agric. Biol. Chem. 1987, 51, 289. 

Sobczak, A. Hartmann, H. Helmchen, G. Tetrahedron Lett. 

Lavallee, R Ruel, R. Grenier, L. Bissonnette, M. Tetrahedron Lett. 

Edward J. J. Grabowski Merck Research Laboratories, Rahway, NJ, USA 

Physical Data mp 48-50 °C bp 111-113 °C/19 mmHg. Form Supplied in white solid widely available. 

Boiling point at 760 mm. Hg Flash point, Cleveland open cup Melting point Molecular weight 

---

Compare 2 3 pentanediol and 2 4 pentanediol with respect to the number of stereoisomers possible for each constitution Which stereoisomers are chiraL Which are achiraL... 

Fig. 9. SEM photographs of cellulose acetate membranes cast from a solution of acetone (volatile solvent) and 2-meth5l-2,4-pentanediol (nonvolatile solvent). The evaporation time before the stmcture is fixed by immersion ia water is shown (24).

In this model, the intermediacy of a monomeric zinc species is postulated. To support this assumption, an examination of the effect of stoichiometry and solvent in cyclopropanation involving the 2,4-pentanediol auxiliary was preformed [59]. In the initial reaction protocol, a large excess of both diethylzinc and diiodo-methane is employed. Such excessive conditions are justified on account of the instability of the zinc carbenoid under the reaction conditions. To minimize the un-... 

The method of Ito et at. 50) as applied by Bakos et at. 12) to the reduction of acctylacetone to either ( —)-(2R,4J )- or ( + H25,45)-2,4-pentanediol will serve to illustrate how a chiral heterogeneous catalyst has been used to prepare a chiral homogeneous ligand precursor. 

A third route to nonracemic a-alkoxy and a-hydroxy stannaries employs the chiral acetal 73 prepared from (f ,f )-2,4-pentanediol (Scheme 30)66. Addition of various Grignard reagents to this acetal in the presence of TiCLt results in selective displacement yielding (S )-a-alkoxy stannanes. The corresponding a-hydroxy derivatives can be obtained after oxidation and mild base treatment. Organocuprates can also be employed to cleave this acetal but with somewhat lower selectivity67. 

From a practical point of view, the catalytic asymmetric hydrogenation of the corresponding diones will be the preferred method if high yields and high enantioselectivity can be ensured. Recently, over 98% yield with more than 99% ee has been achieved by optimizing the reaction conditions.64 For example, asymmetric hydrogenation of 2,4-pentanedione catalyzed by Ru-BINAP complex in the presence of hydrochloric acid gave 2,4-pentanediol in more than 95% yield and over 99% ee (Scheme 6-29).64... 

Reduction of diketones such as pentane-2,4-dione using (RfBiNAP-RuCF under hydrogen (75 100 atm) gives the corresponding diol, in this case (R),(R)-2,4-pentanediol with an excellent diastereomer ratio (98 %) and optical purity (>99 %)[48]. 

---