title: Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate.
abstract: Esters of crotonic acid were brominated on a multigramme scale using a free radical procedure. A phase transfer catalysed fluorination transformed these species to the 4-fluorobut-2E-enoates reproducibly and at scale (48-53%, ca. 300 mmol). Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four diastereoisomers of a versatile fluorinated C4 building block at high enantiomeric-enrichment. The (DHQ)2AQN and (DHQD)2AQN ligands described by Sharpless were the most effective. The development and optimisation of a new and facile method for the determination of ee is also described; (19)F{(1)H} spectra recorded in d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers.
authors.affiliation: WestCHEM Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom ; Carbosynth Ltd., 93 Innovation Drive, Milton Park, Abingdon, Oxfordshire OX14 4RZ, United Kingdom.
authors.forename: James A B
authors.initials: JA
authors.lastname: Laurenson
authors.affiliation: WestCHEM Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.
authors.forename: John A
authors.initials: JA
authors.lastname: Parkinson
authors.affiliation: WestCHEM Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Percy
authors.affiliation: WestCHEM Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rinaudo
authors.affiliation: Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom ; Lallemand Gb Ingredients, Dock Road, Felixstowe, Suffolk IP11 3QW, United Kingdom.
authors.forename: Ricard
authors.initials: R
authors.lastname: Roig
keywords: asymmetric; dihydroxylation; ee determination; fluorination; fluorosugars; organo-fluorine