Control of 6-Exo and 7-Endo Cyclizations of Alkynylamides using Platinum and Bismuth Catalysts

Synthesis of (Z)-β-Chloro-enamides via a Base-Promoted trans-Hydroamidation of Alkynyl Chlorides Using 1,1-Dichloroalkenes as Precursor

An efficient and general base-promoted reaction of 1,1-dichloroalkenes with secondary sulfonamides and amides for the synthesis of (Z)-β-chloro-enamides has been described. This reaction exhibits functional group tolerance under simple and mild conditions. Mechanistic study indicated that a stereoselective trans-hydroamidation of alkynyl chlorides generated in situ from 1,1-dichloroalkenes was the key step.

Synthesis of 1,4-diazepinone derivatives via a domino aza-Michael/SN2 cyclization of 1-azadienes with α-halogenoacetamides

A novel cyclization of α-halogenoacetamides with 1-azadienes has been developed for the efficient preparation of monocyclic 1,4-diazepinones in one step under transition metal-free conditions. Various α-halogenoacetamides and 1-azadienes are well tolerated and give the desired products in good to excellent yields. This cyclization also demonstrates potential synthetic utility on a gram-scale and further transformation.

Total Synthesis of Caprazamycin A: Practical and Scalable Synthesis of syn-β-Hydroxyamino Acids and Introduction of a Fatty Acid Side Chain to 1,4-Diazepanone

The first total synthesis of caprazamycin A (1), a representative liponucleoside antibiotic, is described. Diastereoselective aldol reactions of aldehydes 12 and 25-27, derived from uridine, with diethyl isocyanomalonate 13 and phenylcarbamate 21 were investigated using thiourea catalysts 14 or bases to synthesize syn-β-hydroxyamino acid derivatives. The 1,4-diazepanone core of 1 was constructed using a Mitsunobu reaction, and the fatty acid side chain was introduced using a stepwise sequence based on model studies. Notably, global deprotection was realized using palladium black and formic acid without hydrogenating the olefin in the uridine unit.

Metal-catalyzed regiodivergent organic reactions

This review discusses metal-catalysed regiodivergent additions, allylic substitutions, CH-activation, cross-couplings and intra- or intermolecular cyclisations.

Indium-Catalyzed Intramolecular Hydroamidation of Alkynes: An Exo-Dig Cyclization for the Synthesis of Pyranoquinolines through Post-Transformational Reaction

An efficient approach for the synthesis of pyranoquinolines through the indium-catalyzed activation of alkynes is reported. Intramolecular hydroamidation of alkynes can proceed through alkyne activation by indium(III) and then 6-exo-dig cyclization, leading to a fused pyran ring with high selectivity, high atom economy, and good to excellent yields. The cyclization was accomplished through the oxygen, not the nitrogen, of the amide functional group.

Synthesis of CPZEN-45: Construction of the 1,4-Diazepin-2-one Core by the Cu-Catalyzed Intramolecular Amidation of a Vinyl Iodide

CPZEN-45 was developed as an antibiotic against Mycobacterium tuberculosis by the chemical modification of caprazamycins. CPZEN-45 has been synthesized in this study by the Cu-catalyzed intramolecular amidation of a complex vinyl iodide precursor bearing uridine and sugar moieties with a secondary amide, allowing for the construction of its 1,4-diazepin-2-one core.

Synthesis of morpholine or piperazine derivatives through gold-catalyzed cyclization reactions of alkynylamines or alkynylalcohols

A gold catalyzed reaction for the preparation of morpholine and piperazine derivatives from alkynylalcohols or alkynylamines was developed.

Synthesis of quinoxalines or quinolin-8-amines from N-propargyl aniline derivatives employing tin and indium chlorides

The utility of stannous chloride dihydrate as well as indium/InCl₃ in combination with “ortho-nitrogen”-N-propargylanilines for the construction of either quinoxaline- or quinolin-8-amine-scaffolds is demonstrated. Depending on the nature of the alkyne, different bicyclic nitrogen heterocycles are formed under aerobic conditions.

Catalytic asymmetric total synthesis of (+)-caprazol

Catalytic asymmetric total synthesis of caprazol, a lipo-nucleoside antibiotic, has been accomplished employing two of the stereoselective C-C bond forming reactions as key transformations. The stereochemistries of the β-hydroxy-α-aminoester moiety at the juncture of the uridine part and diazepanone part, and of the β-hydroxy-α-amino acid moiety embedded in the diazepanone system, were constructed using a diastereoselective isocyanoacetate aldol reaction (dr = 88:12) and an enantioselective anti-nitroaldol reaction catalyzed by a Nd/Na-chiral amide ligand (dr = 12:1, 95% ee), respectively.

New trends in bismuth-catalyzed synthetic transformations

This review covers uses of bismuth catalysts since 2005 with a special emphasis on the emerging applications of such catalysts. Low toxicity, low catalytic loading, synergistic effects with other catalysts, and some hydrocompatibility properties confer to bismuth salts major advantages. The expanding activity in the field clearly highlights the growing potential of bismuth catalysts. The article is not a comprehensive review on bismuth catalysis but a selection of its most promising uses in challenging synthetic transformations.

The outcome of the oxidations of unusual enediamide motifs is governed by the stabilities of the intermediate iminium ions

We compare the results from the oxidation of two unusual "enediamide" motifs (3,4-dihydropyrazin-2(1H)-ones), where a double bond is flanked by two amides. In one case the oxidation led to a ring-opened product arising from the cleavage of the double bond, and in the other a rare cis-dioxygenated compound was obtained. Both products have been characterized by X-ray crystallography. The outcomes of the key reactions are rationalized based on calculated free energies of intermediates.