RESUMO
A convenient strategy is presented for the easy preparation of a series of 2 H-chromenes under mild conditions through iodocyclization of readily accessible propynols. In addition, various 4-chromanones can be synthesized through a p-toluenesulfonic acid catalyzed cascade cyclization with high efficiency (yields up to 99 %). Our developed reaction systems are proven to have good functional-group applicability and can be scaled up to gram quantities in satisfactory yields. These systems also provide a new synthetic strategy for two types of important flavonoid skeleton without using costly and toxic metal catalysts. Additionally, the resulting halides could be further exploited in subsequent palladium-catalyzed coupling reactions, so these compounds could act as potential intermediates for the construction of some valuable drug molecules.
RESUMO
A copper-catalyzed difunctionalizing trifluoromethylation of activated alkynes with the cheap reagent sodium trifluoromethanesulfinate (NaSO2CF3 or Langlois' reagent) has been developed incorporating a tandem cyclization/dearomatization process. This strategy affords a straightforward route to synthesis of 3-(trifluoromethyl)-spiro[4.5]trienones, and presents an example of difunctionalization of alkynes for simultaneous formation of two carbon-carbon single bonds and one carbon-oxygen double bond.
Assuntos
Alcinos/química , Cobre/química , Compostos de Espiro/síntese química , Alcinos/síntese química , Catálise , Ciclização , Halogenação , Metilação , Oxirredução , Compostos de Espiro/químicaRESUMO
A silver-catalyzed oxidative cyclization of 2- or 3-propargylamide-substituted indoles to synthesize phosphorated indoloazepinone derivatives is described. This reaction displays a difunctionalizalion of alkynes with diphenylphosphine oxides to construct a seven-membered ring through a radical cyclization process. The indoloazepinones derivatives are common structural motifs found in many natural products and pharmaceuticals.
Assuntos
Azepinas/síntese química , Indóis/síntese química , Prata/química , Alcinos/química , Azepinas/química , Catálise , Ciclização , Indóis/química , Estrutura Molecular , Oxirredução , EstereoisomerismoRESUMO
A novel copper-catalyzed difluoromethylation of 2- or 3-propargylamide-substituted indoles with ICF2CO2Et via a radical cascade cyclization process is described. A wide substrate scope is compatible with the reaction conditions to synthesize mono- and bis-difluoromethylated indoloazepinone derivatives, which contain a seven-membered ring.
RESUMO
A AgSCF3-mediated radical cascade cyclization/trifluoromethylthiolation of 1,6-enynes triggered by a C-C triple bond is developed. This protocol also provides another opportunity to construct a valuable trifluoromethylthio-substituted polycyclic fluorene system through the formations of one C-SCF3 bond and two C-C bonds in a single step.
RESUMO
A novel and highly practical reaction for the copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes is presented here. This methodology provides a general and straightforward way to synthesize a variety of useful CF3-containing nitriles, which can be used for further preparation of pharmaceutically and agrochemically important compounds in synthetic organic chemistry.
Assuntos
Alcenos/química , Cobre/química , Hidrocarbonetos Fluorados/síntese química , Nitrilas/síntese química , Compostos Organometálicos/química , Catálise , Hidrocarbonetos Fluorados/química , Metilação , Estrutura Molecular , Nitrilas/químicaRESUMO
A novel three-component strategy for the cyanotrifluoromethylation/azidotrifluoromethylation and carbocyclization of 1,6-enynes is developed. The reaction proceeds smoothly under a moderate temperature by using a copper catalyst, which provides a rapid and concise access to addition-carbocyclization products. Furthermore, the products obtained can be useful building blocks in discoveries of lead compounds and other biologically active CF3-containing heterocycles.
RESUMO
A new and efficient metal-free cascade cyclization of 1,6-enynes with aldehydes is developed for the synthesis of tricyclic fluorene derivatives. The reaction involves a radical process and one C(sp(2))-C(sp(2)) and two C(sp(2))-C(sp(3)) bonds are formed simultaneously in one pot by using PivOH and TBHP.
Assuntos
Aldeídos/química , Alcenos/química , Alcinos/química , Fluorenos/síntese química , Ciclização , Fluorenos/química , Radicais Livres/químicaRESUMO
A direct nitration of aromatic sulfonamides using sodium nitrite as the nitrating agent has been developed. The reaction shows typically mono-substitution selectivity and can be enlarged to the gram scale with good yield.