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)-

Cascade reactions provide a straightforward access to many valuable compounds and reduce considerably the number of steps of a synthetic sequence. Among the domino and multicomponent processes that involve alkynes, the cascade reaction between alkynoic acids and C-, N-, O- and S-aminonucleophiles stands out as a particularly powerful tool for the one-pot construction of libraries of nitrogen-containing heterocyclic compounds with scaffold diversity and molecular complexity. This reaction, based on an initial metal-catalyzed cycloisomerization that generates an alkylidene lactone intermediate, was originally catalyzed by gold(I) catalysts, along with silver salts or Brönsted acid additives, but other alternative metal catalysts have emerged in the last decade as well as different reaction media. This review examines the existing literature on the topic of metal-catalyzed cascade reactions of acetylenic acids and dinucleophiles and discusses aspects concerning substrate/catalyst ratio for every catalyst system, nature of the aminonucleophile involved and substrate scope. In addition, alternative solvents are also considered, and an insight into the pathway of the reaction and possible intermediates is also provided.

Catalysis by first-row transition metals is of increasing interest in the context of the scarcity of chemical resources. For instance, iron is promising due to its abundance, low toxicity and unique electronic features. Here we synthesized quinazoline alkaloids from alkynoic acids and functionalized amines in the presence of iron dibromide and pyridine in toluene or, alternatively, in a solventless reaction system. We studied iron sources, reaction media and the effect of additives. Results show 39–99% yields and regioselective preparation of nitrogen- and oxygen-containing scaffolds. This is the first example of a cascade process involving alkynoic acids catalyzed by iron. Fe is more abundant, cheaper and less toxic than other Au, Cu and Ru catalysts previously reported for similar transformations.

Cesium Carbonate-Promoted Hydroamidation of Alkynes: Enamides, Indoles and the Effect of Iron(III) Chloride. -A simple procedure for the title synthesis is developed by using a mild base. In some cases the addition of a catalytic amount of FeCl3·6H2O gives better yields. The unprotected indoles are obtained from the N-acylated anilides with exception of the compound (XVI). -(HERRERO, M. T.; DIAZ DE SARRALDE, J.; SANMARTIN, R.; BRAVO, L.; DOMINGUEZ*, E.; Adv. Synth. Catal. 354 (2012) 16, 3054-3064, http://dx.