title: Asymmetric allylation of methyl ketones by using chiral phenyl carbinols.
abstract: Novel chiral auxiliaries for the stereoselective allylation of aliphatic methyl ketones with allyltrimethylsilane and their use in the synthesis of homoallylic ethers are described. In a multicomponent domino process catalyzed by trifluoromethanesulfonic acid, the allyl moiety and the auxiliary are transferred onto the substrate to yield tertiary homoallylic ethers. The most useful auxiliary for a general application turned out to be the trimethylsilyl ether of phenyl benzyl carbinol with an induced diastereoselectivity of 90:10 using ethyl methyl ketone and 94:6 using isopropyl methyl ketone as substrates. The transferred substituted benzyl moiety has good protecting properties in subsequent transformations and can easily be removed under reductive conditions to provide the corresponding homoallylic alcohol. The origin of the high selectivity could be elucidated by identifying the relevant transition states using quantum-chemical calculations. An excellent agreement between calculated and experimentally observed selectivities was obtained assuming an oxocarbenium ion as intermediate.
authors.affiliation: Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany. ltietze@gwdg.de
authors.forename: Lutz F
authors.initials: LF
authors.lastname: Tietze
authors.forename: Tom
authors.initials: T
authors.lastname: Kinzel
authors.forename: Thomas
authors.initials: T
authors.lastname: Wolfram
mesh_terms: D000438:Alcohols / Q000737:chemistry; D000498:Allyl Compounds / Q000737:chemistry*; D001592:Benzyl Alcohols / Q000737:chemistry*; D006588:Hexanones / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000438:Alcohols; D000498:Allyl Compounds; D001592:Benzyl Alcohols; D006588:Hexanones