Trends in Organocatalytic Conjugate Addition to Enones: An Efficient Approach to Optically Active Alkynyl, Alkenyl, and Ketone Products

Organocatalytic Dearomative Spirocyclization Reaction of Enone-Tethered α-and β-Naphthols and Dearomatization Reaction of In Situ Generated Nitro-Olefin-Tethered α-Naphthols

Herein, we report a catalytic dearomative spirocyclization reaction of new substrates having aryl/alkyl enone tethered α- and β-naphthols and a dearomatization reaction of in situ generated nitro-olefin-tethered α-naphthols. The spirocarbocycles were obtained in moderate to good yields with high diastereoselectivities. A preliminary catalytic asymmetric variant was reported. A few applications such as hydrogenations and epoxidation reaction have also been demonstrated. Theoretical study has also been performed to understand high diastereoselectivity in the triethylamine catalyzed spirocyclization reaction.

An acid-promoted pseudocine substitution manifold of γ-aminocyclopentenone enables divergent access to polycyclic indole derivatives

We demonstrated γ-aminocyclopentenones to be a suitable surrogate for reactive cyclopentadienone via a pseudocine-substitution manifold. This approach enabled its orchestrated annulation with "tailored" bis-nucleophiles and to furnish complex β,γ-annulated cyclopentanoids or indole-based polycyclic architectures. This strategy represents a generalized means for direct, regioselective and stereoselective β,γ-functionalization of monosubstituted or unsubstituted aminocyclopentenones.

Cu-catalyzed coupling of indanone oxime acetates with thiols to 2,3-difunctionalized indenones

A Cu-catalyzed coupling reaction of indanone oxime acetates with thiols has been developed for the synthesis of 2,3-functionalized 1-indenones. This protocol has several features including easy mild reaction conditions, stabilized enamine products, good tolerance of functional groups, and no external oxidants. This reaction enables direct derivatization on the indanone ring to provide valuable functionalized indenones at room temperature.

Acid-Controlled Access to β-Sulfenyl Ketones and α,β-Disulfonyl Ketones by Pummerer Reaction of β-Keto Sulfones and Sulfoxides

A convenient acid-mediated reaction of β-keto sulfones with sulfoxides under metal-free conditions has been developed, thereby delivering the acid-controlled synthesis of β-sulfenyl ketones and α,β-disulfonyl ketones in good to excellent yields. The mechanism of the transformations has been studied carefully, which suggested the involvement of a radical process in the formation of α,β-disulfonyl ketones.

Stereodivergent synthesis of alkenes by controllable syn-/anti-fragmentation of β-hydroxysulfonyl intermediates

Complementary fragmentation mechanisms of Hawkins and one-pot Julia olefinations were employed for the stereodivergent synthesis of alkenes.

Formation of quaternary centres by copper catalysed asymmetric conjugate addition to β-substituted cyclopentenones with the aid of a quantitative structure-selectivity relationship

A new asymmetric conjugate addition method was developed for β-substituted cyclopentenones to form quaternary centres using alkylzirconocene nucleophiles giving up to 97% yield and 92% ee.

A new asymmetric conjugate addition method was developed for β-substituted cyclopentenones to form quaternary centres using alkylzirconocene nucleophiles giving up to 97% yield and 92% ee. Key to the reaction's success was the design of suitable phosphoramidite ligands which was aided by a linear quantitative structure–selectivity relationship (QSSR). QSSR models were created from the ligand screening data (a total of 36 ligands) which revealed important electronic and steric requirements and led to the synthesis of more enantioselective ligands. DFT calculations of competing transition structures enable the interpretation of the electronic and steric terms present in the QSSR models.

Synthesis of α-sulfenyl monoketones via a metal-free oxidative cross dehydrogenative coupling (CDC) reaction

α-Sulfenyl ketones are potential precursors which find a variety of applications in organic synthesis.

Enantioselective syntheses of indanes: from organocatalysis to C–H functionalization

The indanyl core is ubiquitous in a large variety of drugs and natural products. Remarkable recent progress has been accomplished in the step-economical assembly of functionalization of chiral indanes by means of enantioselective catalysis, with major progress being achieved in organocatalysis and C–H activation chemistry.

Double Smiles rearrangement of Passerini adducts towards benzoxazinones

A new straightforward access to benzoxazinones based on a three-component coupling is presented here.

Molecular assembly of an achiral phosphine and a chiral primary amine: a highly efficient supramolecular catalyst for the enantioselective Michael reaction of aldehydes with maleimides

A combined catalyst system of a cinchonidine-derived primary amine and triphenylphosphine (CD-NH2 /PPh3 ) exhibited high catalytic performance in the Michael reaction of aldehydes with maleimides, thereby affording the corresponding functionalized aldehydes in excellent yields (up to 99 %) and enantioselectivities (>99 % ee). More interestingly, the significance of the phosphine in enhancing the enantioselectivities in the chiral-primary-amine-catalyzed Michael reaction was revealed. Furthermore, we explored the origin of the reaction mechanism in the Michael addition promoted by the dual organocatalytic system. On the basis of experimental results and spectroscopic analysis, such as UV/Vis, fluorescence emission (FL), NMR, and circular dichroism (CD) spectroscopy, as well as ESI-MS, we found that the molecular assembly of phosphine and primary amine played a crucial role in this enantioselective reaction, in which a possible supramolecular complex was formed as an effective chiral catalyst through noncovalent molecular interactions of a cinchona alkaloid-derived primary amine with triphenylphosphine.

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

Four catalysts based on new amides of chiral 1,2-diamines and 2-sulfobenzoic acid have been developed. The alkali-metal salts of these betaine-like amides are able to form imines with enones, which are activated by Lewis acid interaction for nucleophilic attack by 4-hydroxycoumarin. The addition of 4-hydroxycoumarin to enones gives ee's up to 83% and almost quantitative yields in many cases. This novel type of catalysis provides an effective alternative to conventional primary amino catalysis were strong acid additives are essential components.

Cinchona-based primary amine catalysis in the asymmetric functionalization of carbonyl compounds

Asymmetric aminocatalysis exploits the potential of chiral primary and secondary amines to catalyze asymmetric reactions. It has greatly simplified the functionalization of carbonyl compounds while ensuring high enantioselectivity. Recent advances in cinchona-based primary amine catalysis have provided new synthetic opportunities and conceptual perspectives for successfully attacking major challenges in carbonyl compound chemistry, which traditional approaches have not been able to address. This Review outlines the historical context for the development of this catalyst class while charting the landmark discoveries and applications that have further expanded the synthetic potential of aminocatalysis.

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.

A simple recipe for sophisticated cocktails: organocatalytic one-pot reactions--concept, nomenclature, and future perspectives

Asymmetric organocatalysis has been successfully incorporated in many multistep one-pot sequences to provide simple access to structurally complex target molecules in a highly stereoselective fashion. The key feature behind this success is the ability of organocatalyzed reactions to proceed efficiently in the presence of large amounts of spectator reagents. Additionally, owing to their organic nature and substoichiometric presence, organocatalysts are also expected to become innocent bystanders in subsequent transformations. In this Minireview, an easy-to-use classification and nomenclatural system that is capable of systematically and informatively describing each one-pot reaction is introduced, and selected important contributions within the field of organocatalytic one-pot reactions are reviewed according to this new system. Finally, future developments and perspectives in the field are discussed.

Organocatalytic asymmetric halogenation/semipinacol rearrangement: highly efficient synthesis of chiral α-oxa-quaternary β-haloketones

A novel asymmetric halogenation/semipinacol rearrangement reaction catalyzed by cinchona alkaloid derivatives was developed. Two types of β-haloketones (X = Br, Cl) were obtained with up to 95% yield and 99% enantiomeric excess. The desired (+) and (-) enantiomers of the β-haloketones were readily obtained.

Asymmetric organocatalytic monofluorovinylations

The development of highly enantio- and diastereoselective organocatalytic monofluorovinylations is presented. Based on the application of α-fluoro-β-keto-benzothiazolesulfones, the formal addition of a monofluorovinylic anion synthon to a range of acyclic and cyclic enones, as well as imines, is shown. These procedures give selective access to both E- and Z-isomers of the monofluorovinylated products, which are isolated as the pure diastereoisomers in good to excellent yields with up to 99% ee. Furthermore, the application of this concept for the formation of highly enantioenriched bicylic compounds containing a monofluorovinyl moiety is also described. In addition, a mechanistic rationale for the observed E:Z-selectivities is presented.