Gold(I)-Catalyzed Cascade Cyclization Reactions of Allenynes for the Synthesis of Fused Cyclopropanes and Acenaphthenes
A gold-catalyzed reaction of phenylene-tethered allenynes with benzofurans gave 1-(naphth-1-yl)cyclopropa[b]benzofuran derivatives, whereas the reaction of 1-allenyl-2-ethynyl-3-methylbenzene derivatives in the absence of benzofurans gave acenaphthenes in good yields. These results can be rationalized by nucleophilic attack of the alkyne moiety on an activated allene to form a vinyl cation intermediate.
Synthesis of functionalized benzo[b]thiophenes by the intramolecular copper-catalyzed carbomagnesiation of alkynyl(aryl)thioethers
Highly functional: A copper(I)-catalyzed intramolecular carbomagnesiation under mild conditions transforms readily available alkynyl(aryl)thioethers into magnesiated benzothiophenes. Subsequent reaction with various electrophiles (acid chlorides, allyl bromides, aryl halides) provides polyfunctional benzo[b]thiophenes (see scheme). Further modification of the cyclization products affords highly diversified benzothiophene derivatives and new heterocyclic scaffolds.
Kunz, Thomas,Knochel, Paul
supporting information; experimental part
p. 1958 - 1961
(2012/04/18)
Palladium-catalyzed aryl amination-heck cyclization cascade: A one-flask approach to 3-substituted indoles
(Chemical Equation Presented) Two for the price of one: A Pd/dppf-based catalyst provides access to the title compounds from 1,2-dihalogenated aromatic compounds and allylic amines in a single reaction flask. The initial aryl amination step occurs with excellent selectivity for the aryl iodide to ensure the formation of a single indole regioisomer, which can be functionalized in situ by N-arylation (see scheme). dba = dibenzylideneacetone, dppf = 1,1′-bis(diphenylphospanyl)ferrocene.