Evans-Chapman-Carreira reduction

In 1986, Evans and colleagues introduced tetramethylammonium triacetoxyboro-hydride, a mild reducing reagent for the highly diastereoselective synthesis of 1,3-anft-diols from acyclic (3-hydroxy ketones1 (Scheme 4.2a). The reaction, commonly called the Evans-Chapman-Carreira reduction, is typically carried out in a 1 1 mixture of anhydrous acetic acid and acetonitrile, as the reaction needs to be run at low temperature in the presence of acetic acid. An important observation is that the anti -diastereoselectivity is realized regardless of the stereochemistry of the a-alkyl substituent Both anti - and. vvn-a.-methyl-(3-hydroxy... 

In theory, the chiral center can be anywhere in the molecule, but in practice, reasonable diastereoseleclivily is most often achieved when il is in the a position. For examples of high diaslereoselectivity when the chiral center is further away, especially in reduction of p-hydroxy ketones, see Narasaka Pai Tetrahedron 1984, 40, 2233 Hassine Gorsane Pecher Martin Bull. Soc. Chim. Belg. 1985, 94, 597 Bloch Gilbert Girard Tetrahedron Lett. 1988, 53, 1021 Evans Chapman Carreira J. Am. Chem. Soc. 1988, 110, 3560. 

Evans DA, Chapman KT, Carreira EM. Directed reduction of beta-hydroxy ketones emplo3dng tetramethylammonium tri-acetoxyborohydride. J. Am. Chem. Soc. 1988 10(11) 3560-3578. 

---