Alexis Coste

Ynamides: Versatile Tools in Organic Synthesis

Ynamides display an exceptionally fine balance between stability and reactivity. They also offer unique and multiple opportunities for the inclusion of nitrogen-based functionalities into organic molecules, and are emerging as especially useful and versatile building blocks for organic synthesis. Recent breakthroughs in the preparation of these substrates have revitalized interest in nitrogen-substituted alkynes, and the beginning of the 21st century has witnessed an ever-increasing number of publications reporting the development of new reactions or synthetic sequences starting from ynamides. This Review highlights major developments in this area.

Copper‐Mediated Coupling of 1,1‐Dibromo‐1‐alkenes with Nitrogen Nucleophiles: A General Method for the Synthesis of Ynamides

Mild reaction conditions are the advantage of the title reaction, which allows straightforward entry to a variety of ynamides starting from readily available 1,1-dibromo-1-alkenes, which act as attractive alkynylating agents (see scheme; EWG = electron-withdrawing group, DMF = N,N-dimethylformamide).

Copper-catalyzed cyclization of iodo-tryptophans: A straightforward synthesis of pyrroloindoles

Pyrroloindoles are a key structural motif found in a wide number of biologically active alkaloids. Intramolecular copper-catalyzed coupling of readily accessible 2-iodo-tryptophan derivatives occurs in excellent yield, affording a wide range of polysubstituted, enantioenriched tetrahydropyrrolo[2,3- b]indoles. Diketopiperazines are also suitable substrates for this cyclization reaction, which affords a straightforward entry to tetra- to hepta-polycyclic systems.

Synthesis of Ketene N,N-Acetals by Copper-Catalyzed Double-Amidation of 1,1-Dibromo-1-alkenes

An efficient procedure for the preparation of ketene N,N-acetals by copper-catalyzed double amidation of 1,1-dibromo-1-alkenes is reported. The reaction was found to be general, and ketene aminals could be obtained in good yields when potassium phosphate in toluene was used at 80 degrees C. The reaction was found to proceed through a regioselective monocoupling reaction followed by dehydrobromination and hydroamidation.

Copper-catalyzed cyclization reactions for the synthesis of alkaloids

Copper-mediated Ullmann type transformations have recently evolved as useful and valuable synthetic tools in organic synthesis. If newly developed catalytic systems are readily available, inexpensive, and tolerate most functional groups, they also provide new opportunities in natural product synthesis since they allow new and efficient retrosynthetic disconnections. They are also especially convenient for the development of straightforward cyclization and macrocyclization procedures. The present article showcases some examples of copper-catalyzed cyclization reactions for the synthesis of alkaloids we have recently developed.

Direct C-glycosylation by indium-mediated alkynylation on sugar anomeric position.

Indium-mediated alkynylation reaction was studied for the direct preparation of C-glycosides. Easily available starting sugar derivatives with an acetyl group at the anomeric position were tested as electrophiles toward alkynylindium reagents under Barbier conditions. Good yields and stereoselectivities were observed during the reaction. The alkynylation was applied to the synthesis of an alpha-(1-->6)-C-disaccharide analogue of isomaltoside.

A convergent synthesis of the fully elaborated macrocyclic core of TMC-95A.

A concise and straightforward synthesis of the fully elaborated macrocyclic core of TMC-95A is reported. A highly efficient organocatalyzed aldolization between isatin and dihydroxyacetone derivatives and formation of the biaryl subunit with concomitant macrocyclization are the characteristic features of this synthesis.