| Autor: |
Fotini Moschona, Christina Misirlaki, Nikolaos Karadimas, Maria Koutiva, Ioanna Savvopoulou, Gerasimos Rassias |
| Jazyk: |
angličtina |
| Rok vydání: |
2022 |
| Předmět: |
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| Zdroj: |
Symmetry, Vol 14, Iss 5, p 989 (2022) |
| Druh dokumentu: |
article |
| ISSN: |
2073-8994 |
| DOI: |
10.3390/sym14050989 |
| Popis: |
The intramolecular halocyclization of alkenes possessing an internal heteroatom nucleophile leads to multifunctional heterocycles which are useful versatile intermediates in organic synthesis. The asymmetric chlorocyclisation of 2-substituted allylic amides gives access to chiral oxazolines bearing a chloromethyl moiety for further synthetic manipulation. The literature reports on this transformation involve complex syntheses of the 2-substituted allylic amides and cryogenic temperatures for achieving high enantioselectivities in the organocatalyzed halocyclization step. Based on the Heck reaction of aryl bromides and Boc-protected allylamine or allylamine benzamides, we developed a practical synthesis of 2-substituted allylic amides that does not require chromatography and accomplished their asymmetric halocyclization reaction with 24–92%ee under practical conditions (5 °C, CpME) catalyzed by (S)-(+)-DTBM-SEGPHOS. In addition, using appropriately substituted substrates, we generated Hammett plots and formulated a consistent mechanism for the halocyclization reaction which involves two competing modes of formation of the haliranium intermediate whose relative kinetics are governed by the electronic properties of the substrate. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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