title: Improved synthesis of cyclic tertiary allylic alcohols by asymmetric 1,2-addition of AlMe3 to enones.
abstract: The development of an improved protocol for the enantioselective Rh(I) /binap-catalysed 1,2-addition of AlMe3 to cyclic enones is reported. (31)P NMR analysis of the reaction revealed that the catalyst in its resting state is a chloride-bridged dimer. This insight led to the use of AgBF4 as an additive for in situ activation of the dimeric precatalyst. Thus, the catalyst loading can now be reduced to only 1 mol% with respect to rhodium. Various 5-7-membered cyclic enones can be transformed into tertiary allylic alcohols with excellent levels of enantioselectivity and high yields. The obtained products are versatile synthetic building blocks, shown by a highly enantioselective formal total synthesis of the pheromone (-)-frontalin as well as formation of a bicyclic lactone that has the core structure of the natural flavour component "wine lactone".
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg (Germany), Fax: (+49) 6421-2825362.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kolb
authors.forename: Wei
authors.initials: W
authors.lastname: Zuo
authors.forename: Jürgen
authors.initials: J
authors.lastname: Siewert
authors.forename: Klaus
authors.initials: K
authors.lastname: Harms
authors.forename: Paultheo
authors.initials: P
authors.lastname: von Zezschwitz
keywords: alanes; allylic alcohols; asymmetric catalysis; enones; nucleophilic addition; rhodium