Diastereo- and enantioselective synthesis of oxazine and oxazolidine derivatives with a chiral quaternary carbon center under multifunctional catalysis

Homologation of the Fischer Indolization: A Quinoline Synthesis via Homo-Diaza-Cope Rearrangement

We disclose a new Brønsted acid promoted quinoline synthesis, proceeding via homo-diaza-Cope rearrangement of N-aryl-N'-cyclopropyl hydrazines. Our strategy can be considered a homologation of Fischer's classical indole synthesis and delivers 6-membered N-heterocycles, including previously inaccessible pyridine derivatives. This approach can also be used as a pyridannulation methodology toward constructing polycyclic polyheteroaromatics. A computational analysis has been employed to probe plausible activation modes and to interrogate the role of the catalyst.

Nine-step total synthesis of (−)-strychnofoline

The asymmetric synthesis of an anti-cancer spirooxindole alkaloid, (−)-strychnofoline, has, for the first time, been accomplished in only nine steps.

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

Organocatalysis, now running its second decade of life, is being considered one of the main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented.

Catalytic asymmetric α-amination of β-keto esters and β-keto amides with a chiral N,N′-dioxide–copper(i) complex

The highly efficient asymmetric α-amination of β-keto esters and β-keto amides was realized by using a chiral N,N′-dioxide/Cu(i) complex. Under mild reaction conditions, a series of chiral α-amino dicarbonyl compounds were obtained in good result.

An Exploration of Organocatalyst 1,4-Diazabicyclo[2.2.2]octane in the Direct Regioselective and Chemoselective γ-Addition of β-Keto Amide on Isatin to Afford Structurally Diverse Molecular Frameworks

An efficient protocol promoted by 1,4‐diazabicyclo[2.2.2]octane is described for the regioselective and chemoselective γ-addition of β-keto amides on isatins to afford γ-(3-hydroxy-2-oxindole)-β-keto amide structural framework under metal-free conditions. The developed method is mild, generates high yields, and is applicable for a variety of isatin electrophiles as well as β-keto amides. Moreover, the procedure is very handy and environmentally benign in nature, and provides direct access for the synthesis of diverse functionalized 3-β-keto amide-substituted 3-hydroxy-2-oxindole structural scaffolds from readily available starting materials.

Origin of the enantioselectivity in organocatalytic Michael additions of β-ketoamides to α,β-unsaturated carbonyls: a combined experimental, spectroscopic and theoretical study

The organocatalytic enantioselective conjugate addition of secondary β-ketoamides to α,β-unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto's thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.

One-pot synthesis of 6,11-dihydro-5H-indolizino[8,7-b]indoles via sequential formation of β-enamino ester, Michael addition and Pictet–Spengler reactions

One pot sequential reaction of generation of β-enamino ester, Michael addition and Pictet–Spengler reaction.

On water: silver-catalyzed domino approach for the synthesis of benzoxazine/oxazine-fused isoquinolines and naphthyridines from o-alkynyl aldehydes

An operationally simple domino approach for the silver-catalyzed synthesis of oxazine/benzoxazine-fused isoquinolines 5a-q and naphthyridines 6a-v by the reaction of o-alkynyl aldehydes 3a-aa with amines having embedded nucleophiles 4a-d under mild reaction condition in water is described. The reaction shows selective C-N bond formation on the more electrophilic alkynyl carbon resulting in the formation of 6-endo-dig cyclized product. The competitive experiments show the viability of an intramolecular nucleophilic attack over an intermolecular attack of the external nucleophile. This methodology accommodates wide functional group variation, which proves to be useful for structural and biological assessment.