Catalytic enantioselective synthesis of 2-aryl chromenes and related phosphoramidite ligands and catalyst compounds
Methods to access 2-aryl chromene compounds via an asymmetric catalytic process.
1. A method for asymmetric synthesis of a 2-aryl chromene compound, said method comprising:
providing a reaction medium comprising an o-arylallyl-substituted phenoxy ester compound of a formula
wherein X is selected from alkylcarbonyl and arylcarbonyl moieties, LG is a leaving group selected from alkoxycarbonyl groups, R is selected from H, halo, alkyl and alkoxy moieties and Ar is selected from aryl and substituted aryl moieties, said substituents selected from halo, alkyl, alkoxy, nitro and haloalkyl substituents, multiple said substituents and combinations thereof;
introducing a palladium (II) catalyst precursor compound and a phosphoramidite ligand compound to said reaction medium; and
reacting said phenoxy ester compound with a base component to promote intramolecular cyclization and provide an asymmetric 2-aryl chromene compound of a formula
2. The method of claim 1 wherein Ar is selected from substituted phenyl and naphthyl moieties.
3. The method of claim 1 wherein X is selected from acetyl and benzoyl moieties.
4. The method of claim 1 wherein LG is selected from acetyloxy and benzoyloxy moieties.
5. The method of claim 1 wherein X is an acetyl moiety, and LG is an acetyloxy moiety.
6. The method of claim 1 wherein said phosphoramidite ligand compound is of a formula
wherein each of R and R 1 is independently selected from alkyl, phenyl, phenylalkyl and cycloalkyl moieties, or where said R and R 1 together provide a divalent alkylene moiety; each R 2 is independently selected from methyl and ethyl moieties, or where said R 2 moieties together provide a divalent moiety selected from alkylene and alkyl-substituted alkylene moieties; and each Ar is independently selected from phenyl and substituted phenyl moieties.
7. The method of claim 6 wherein each of R and R 1 is a chiral CH(CH 3 )C 6 H 5 moiety.
8. The method of claim 6 wherein R and R 1 provide a divalent (CH 2 ) m moiety, where m is an integer selected from 4-6.
9. The method of claim 6 wherein each Ar is a substituted phenyl moiety.
10. The method of claim 9 wherein said phosphoramidite ligand compound is of a formula
wherein each R 3 is independently selected from methyl and ethyl moieties and combinations thereof, and each n is independently an integer selected from 1-3.
11. The method of claim 10 wherein each R 3 is ethyl and each n is 2.
12. The method of claim 10 wherein X is selected from acetyl and benzoyl moieties; and LG is selected from acetyloxy and benzoyloxy moieties.
13. The method of claim 12 wherein X is an acetyl moiety and LG is an acetyloxy moiety.