AI Article Synopsis
- - Esters of crotonic acid were successfully brominated in large quantities using a free radical method, followed by a phase transfer catalyzed fluorination that produced 4-fluorobut-2E-enoates with decent yields (48-53%).
- - This process was furthered by asymmetric dihydroxylation reactions, leading to the creation of all four diastereoisomers of a fluorinated C4 building block with high enantiomeric purity.
- - A new and efficient method for measuring enantiomeric excess (ee) was introduced, utilizing (19)F{(1)H} NMR spectra to distinguish between different enantiomers in a specific solvent mixture.
Article 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.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3869297 | PMC |
| http://dx.doi.org/10.3762/bjoc.9.301 | DOI Listing |
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