Enantioselective Synthesis of a Highly Potent Selective Serotonin Reuptake Inhibitor. An Application of Imidazolidinone Catalysis to the Alkylation of Indoles with an α,β-Disubstituted α,β-Unsaturated Aldehyde

Enantioselective conjugate addition of alkenylboronic acids to indole-appended enones

An enantioselective addition of alkenylboronic acids and alkynylboronic esters to unprotected indole-appended enones is reported. This transformation proceeds with high enantioselectivity and high product yields via the use of catalytic amounts of 3,3'-bis(pentafluorophenyl)-BINOL and Mg(Ot-Bu)(2). A range of α-branched indole derivatives are available from the transformation.

Highly efficient asymmetric organocatalytic Friedel-Crafts alkylation of indoles with alpha,beta-unsaturated aldehydes

The development of an improved organocatalyst, N-isopropylated bipyrrolidine 2a, for the asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-unsaturated aldehydes has been presented. The new organocatalyst readily facilitates the enantioselective alkylation reaction, providing 3-alkylated indoles in good to high yields (62-89%) with high levels of enantioselectivity (80-93% ee) using only 2 mol% of catalyst loading.

Diamine Ligands in Copper-Catalyzed Reactions

The utility of copper-mediated cross-coupling reactions has been significantly increased by the development of mild reaction conditions and the ability to employ catalytic amounts of copper. The use of diamine-based ligands has been important in these advances and in this review we discuss these systems, including the choice of reaction conditions and applications in the synthesis of pharmaceuticals, natural products and designed materials.

Secondary and primary amine catalysts for iminium catalysis

Formation of iminium ions from the condensation of chiral secondary or primary amines with alpha,beta-unsaturated aldehydes or ketones can be used as an effective platform for the acceleration of a wide variety of catalytic asymmetric cycloaddition and conjugate addition reactions. The reversible formation of the active iminium ion species simulates the pi-electronics and equilibrium dynamics traditionally associated with Lewis acid activation of alpha,beta-unsaturated carbonyl compounds lowering the energy level of the LUMO associated with the pi-system and activating subsequent reaction. Importantly, these iminium ion catalysed processes offer the opportunity to conduct reactions in the presence of both moisture and air greatly adding to the practicality and general applicability of the chemistry described. Proposed catalytic cycles and transition state models for the induction of asymmetry provide reliable and robust predictive tools for the outcome of reactions and high functional group tolerance suggests this class of transformation will have broad application in the arena of synthetic organic chemistry as the area matures. This review describes the rapid expansion of iminium ion catalysis over recent years from its conceptual introduction to the development of a whole new arsenal of highly practical and effective methods with which to approach challenging and fundamental bond construction processes.

The advent and development of organocatalysis

The use of small organic molecules as catalysts has been known for more than a century. But only in the past decade has organocatalysis become a thriving area of general concepts and widely applicable asymmetric reactions. Here I present my opinion on why the field of organocatalysis has blossomed so dramatically over the past decade.

Conformationally restricted homotryptamines. Part 4: Heterocyclic and naphthyl analogs of a potent selective serotonin reuptake inhibitor

A series of hybrid molecules containing the cyclopropylmethylamino side chain found in homotryptamine (1S,2S)-2c and an isosteric heteroaryl or naphthyl core were prepared and their binding affinities for the human serotonin transporter determined. The most potent isosteres were CN-substituted naphthalenes. These results demonstrate that isosteric aromatic cores which lack an H-bond donor site may be substituted for the indole nucleus without substantial loss in hSERT binding.

Highly enantioselective michael addition of cyclic 1,3-dicarbonyl compounds to alpha,beta-unsaturated ketones

[reaction: see text] The highly enantioselective Michael addition of 1,3-cyclic dicarbonyl compounds to alpha,beta-unsaturated ketones was reported to be catalyzed by an organic primary amine derived from quinine. A chiral anticoagulant drug, (S)-warfarin, was directly prepared in 96% ee, and other related important adducts were also obtained in excellent enantioselectivity (89-99% ee).

Organocatalytic enantioselective indole alkylations of α,β-unsaturated ketones

The C3-selective enantioselective Michael-type Friedel-Crafts alkylations of indoles with nonchelating alpha,beta-unsaturated alkyl ketones, catalysed by a chiral primary amine derived from natural cinchonine, were investigated. The reactions, in the presence of 30 mol% catalyst, were smoothly conducted at 0 to -20 degrees C. Moderate to good ee (47-89%) has been achieved.

Efficient Friedel–Crafts alkylation of indoles and pyrrole with enones and nitroalkene in water

An operationally simple and entirely green protocol for heteropoly acid (10 mg) catalyst conjugate addition of indoles and pyrrole to unsaturated carbonyl compounds and nitroalkene in water at ambient temperature in good to excellent yields has been developed.

Organocatalytic C3-selective Friedel–Crafts alkylations of indoles with α,β-unsaturated ketones

The use of an equimolar amount of pyrrolidine and HClO4 (30 mol%) was found to be effective in promoting the conjugate addition of indoles to (E)-alpha,beta-unsaturated ketones, affording the corresponding beta-indolyl ketones in excellent yields.

Michael addition of thiols to α-enones in ionic liquids with and without organocatalysts

Seventeen organocatalyts were tested for their ability to catalyst the addition of thiophenols to chalcones in [bmim]PF6. The products were isolated in high yield after a short reaction time, but no stereoselectivity was observed. The reactions also proceeded (without any stereoselectivity) in four other ionic liquids. In contrast, 16% and 26% ee were observed when L-proline and cinchonine, respectively, were used as the catalysts in CH2Cl2. Addition of thiophenols is also catalysed by HCl, as well as D-mandelic and L-tartaric acids. Addition of thiophenols to chalcones also occurred in neat ionic liquids, without any additional catalyst, but the rate of the reaction depended considerably on the structure of ionic liquid. The scope of the non-catalysed reaction in ionic liquids was tested by the reactions of 5 different thiols and 3 different alpha-enones.