Rh-catalyzed isomerization and intramolecular redox reaction of alkynyl ethers affording dihydropyrans and ketoolefins.
J Am Chem Soc
; 131(9): 3166-7, 2009 Mar 11.
Article
em En
| MEDLINE
| ID: mdl-19209935
ABSTRACT
When arylmethyl 4-(sulfonyl)-3-butynyl ether and a catalytic amount of Rh(2)(tfa)(4) (tfa = CF(3)CO(2)-) were heated in toluene, 2-aryl-3-(sulfonyl)-5,6-dihydro-2H-pyran was produced in good yield. Ring closure proceeded in a highly regioselective manner, and no isomeric five-membered product was detected. Alternatively, 2-(5-sulfonyl-4-pentynyl)tetrahydrofuran lacking a benzyl substituent afforded a different product, 9-sulfonyl-1-hydroxy-8-nonen-4-one, upon reaction with the same rhodium catalyst at reflux in wet toluene. Both reactions most likely involve cleavage of the C-H bond alpha to ether in the substrate and subsequent intramolecular transfer of the hydrogen atom to sulfonylacetylene, which is supported by experiments using deuterium-labeled starting materials.
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Base de dados:
MEDLINE
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Idioma:
En
Revista:
J Am Chem Soc
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
Japão