Cesium Carbonate‐Promoted Hydroamidation of Alkynes: Enamides, Indoles and the Effect of Iron(III) Chloride

Abstract

A series of enamide derivatives was prepared by a simple procedure for the hydroamidation of alkynes with amides and sulfonamides. The use of such a mild base as cesium carbonate promotes the latter transformation, and the addition of catalytic amounts of ironA C H T U N G T R E N N U N G (III) chloride has a beneficial effect in the outcome of some of the presented hydroamidation reactions. A range of indoles was also synthe-sized from ortho-alkynylanilides by both complementary procedures, which proved to be useful for the construction of the indoloA C H T U N G T R E N N U N G [1,2-c]quinazoline tetracyclic system from an ortho-(2-aminophenylalkynyl)-

Electrochemically Enabled Intramolecular Aminooxygenation of Alkynes via Amidyl Radical Cyclization

“…The inferior results obtained using stoichiometric oxidant also highlighted the advantage of our electrochemical method. The alkyne substrates are known to undergo base promoted hydroamidation reaction [7c,10] . For example, propargyl carbamate 30 underwent efficient hydroxide‐promoted ionic cyclization to afford oxazolidinone 32 in 78% yield.…”

Iron Catalysis in Organic Synthesis

“…865 In most cases the yields could be improved by adding catalytic amounts of iron(III) chloride hexahydrate and pyridine to the reaction mixture. Several enamides have been synthesized by this method with moderate diastereoselectivities mostly in favor of the Z-isomer (eq a).…”

Iron(III) Chloride/Diorganyl Diselenides Promoted Regio‐ and Stereoselective Cyclization of ortho‐Alkynylanilides: Synthesis of (Z)‐4‐(chalcogen)methylenebenzoxazines

“…To this end, the reaction of ortho-alkyn-A C H T U N G T R E N N U N G ylanilide [19] 1a with diphenyl diselenide and FeCl 3 was optimized in terms of relative rates of reagents, solvent, temperature and reaction time. The large amount of ironA C H T U N G T R E N N U N G (III) chloride required in this cyclization proved to be necessary not only to activate the triple bond [21] but also to promote the selenium incorporation. and diphenyl diselenide (1.0 equiv.…”

“…[23] To obtain further insight in order to rationalize the factors which could govern the mechanism aspect of this cyclization reaction, we performed some control experiments as follows: (a) when diphenyl diselenide was added to a solution of ortho-alkynylanilide 1a and FeCl 3 in CH 2 Cl 2 the reaction gave only traces of product [Scheme 3, Eq. With this information in hand, we assume that: (i) the iron selenolate species [21] coordinates to the carboncarbon bond to generate an intermediate a, [25] which activates the carbon-carbon bond towards oxygen attack, (ii) the anti attack of the oxygen atom on the activated intermediate produces the oxazine-iron species b, which suffers a reductive elimination to give the desired cyclized product 2 (Scheme 4, pathway 1). From this result we conclude that the mechanism by which FeCl 3 promotes the cyclization to form a cyclized Csp 2 À Fe intermediate d (Scheme 4) that could react with diphenyl diselenide to give the product is improbable; (b) when diphenyl diselenide was reacted with FeCl 3 in CH 2 Cl 2 , in the absence of substrate 1a, no PhSeCl was detectable [Scheme 3, Eq.…”