RESUMO
Synthesis of substituted pyridines through a novel aza-annulation of 2-en-4-ynyl azides, derived from MBH-acetates of acetylenic aldehydes, is described. A variety of enynyl azides having aryl, heteroaryl, and alkyl groups on the alkyne functionality successfully participated in the Ag-mediated annulation reaction to provide the corresponding 3,6-disubstituted pyridines. I2-mediated cyclization was found to be controlled by the substituent on the alkyne functionality, which offered the 5-iodo-3,6-disubstituted pyridines from enynyl azides having an electron-rich substituent on the alkyne functionality.
Assuntos
Alcinos/química , Azidas/química , Piridinas/síntese química , Acetatos/química , Aldeídos/química , Catálise , Ciclização , Estrutura Molecular , Piridinas/químicaRESUMO
A new method for the synthesis of 5-substituted furan-3-carboxylates from Morita-Baylis-Hillman acetates of acetylenic aldehydes is reported. The process involves palladium-catalyzed isomerization followed by base-promoted deacetylation and cycloisomerization reactions. The utility of this chemistry is further demonstrated by the synthesis of Elliott's alcohol, a key intermediate of the pyrethroid resmethrins.
Assuntos
Acetatos/química , Álcoois/síntese química , Aldeídos/química , Ácidos Carboxílicos/síntese química , Furanos/síntese química , Acetilação , Álcoois/química , Ácidos Carboxílicos/química , Ciclização , Furanos/química , Estrutura Molecular , EstereoisomerismoRESUMO
A new protocol has been developed for the synthesis of substituted thiophenes under mild and metal-free reaction conditions via the base-promoted thioannulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with potassium thioacetate involving a tandem allylic substitution/deacetylative 5-exo-dig-thiocycloisomerization. The obtained products provide an entry to 4H-thieno[3,2-c]chromene and thieno[3,2-c]dihydroquinoline.
Assuntos
Acetatos/química , Aldeídos/química , Tiofenos/síntese química , Estrutura Molecular , Tiofenos/químicaRESUMO
The asymmetric total synthesis of natural seimatopolide B along with its enantiomer is described starting from readily available 5-hexen-1-ol and 3-buten-1-ol. The key steps involved are Jacobson hydrolytic kinetic resolution, proline-catalyzed α-hydroxylation, Yamaguchi esterification and ring-closing metathesis. This asymmetric total synthesis necessitates the revision of the originally assigned (3R, 6S, 9S)-configuration to (3S, 6R, 9R).
Assuntos
Macrolídeos/química , Macrolídeos/síntese química , Estrutura Molecular , EstereoisomerismoRESUMO
A new entry for the synthesis of functionalized arylidene cyclopentenes under metal-free reaction conditions is disclosed via the base-promoted [4 + 1]-annulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with active methylene derivatives involving tandem allylic substitution followed by 5-exo-dig-carbocyclization.
Assuntos
Acetatos/química , Aldeídos/química , Alcenos/química , Alcinos/química , Ciclopentanos/química , Ciclização , TemperaturaRESUMO
One-pot synthesis of substituted pyrroles by a cascade reaction of azides with Morita-Baylis-Hillman acetates of acetylenic aldehydes is described and the reaction is efficiently mediated by triphenyl phosphine at room temperature. Sodium azide is successfully used to provide N-unsubstituted pyrroles, while alkyl azides afforded the corresponding N-alkylated pyrroles through a sequence of allylic substitution/azide reduction/cycloisomerization reactions. The obtained products have provided a new entry to indolizino indoles, pyrrolo isoquinolines and 8-oxo-5,6,7,8-tetrahydroindolizine.
Assuntos
Acetatos/química , Aldeídos/química , Alcinos/química , Azidas/química , Fosfinas/química , Pirróis/síntese química , Catálise , Ciclização , Indóis/química , Indolizinas/química , Isoquinolinas/química , Estrutura Molecular , Oxirredução , Estereoisomerismo , TemperaturaRESUMO
A mild and metal-free access to 1,2,4-tri or 1,2,4,5-tetrasubstituted pyrroles has been developed by the reaction of Morita-Baylis-Hillman acetates of acetylenic aldehydes with amines and sulfonamides. This new protocol is based on K(2)CO(3)-promoted tandem allylic substitution/cycloisomerization reactions.