Total synthesis of (−)-funebrine via Au-catalyzed regio- and stereoselective γ-butyrolactonization of allenylsilane

Synthesis of Tricyclic Fused 6-5-4 Carbocycles via Acid-Promoted Cascade Intramolecular Cyclization of Allenylsilane-Tethered Cyclohexadienones

The reaction of 2,5-cyclohexadienones with methylene-tethered allenylsilane in the presence of Lewis or Brønsted acids leads to a cascade of intramolecular cyclization, yielding stereoselective tricyclic fused 6-5-4 carbocycles featuring a silyl-methylenecyclobutane ring. This transformation is notable for the diastereoselective asymmetric desymmetrization of prochiral dienones, attributed to the axial chirality of allene.

Total Synthesis of Hemerocallisamine I Paved by Gram-Scale Synthesis of (2S,4S)-4-Hydroxyglutamic Acid Lactone

Total synthesis of the 2-formylpyrrole alkaloid hemerocallisamine I is presented, both in racemic and enantiopure form. Our synthetic strategy involves (2S,4S)-4-hydroxyglutamic acid lactone as the key intermediate. Starting from an achiral substrate, the target stereogenic centers were introduced by means of crystallization-induced diastereomer transformation (CIDT) in a highly stereoselective fashion. A Maillard-type condensation was crucial to constructing the desired pyrrolic scaffold.

Green and four-component cyclocondensation synthesis and in silico docking of new polyfunctionalized pyrrole derivatives as the potential anticholinesterase agents

Synthesis of new substituted pyrrole scaffolds containing substituted thiadiazol-2-amine moiety was successfully developed through one-pot and multi-component tandem condensation reaction utilizing of triethyl ammonium hydrogen sulfate ([Et3NH][HSO4]) ionic liquid as a green media under solvent-free conditions. The chemical structures of all newly synthesized compounds were fully characterized by spectroscopic methods (IR, ¹H NMR, ¹³C NMR) and elemental analyzes. The molecular docking studies were also performed to predict the possible binding sites of the derivatives on the active site gorge of cholinesterase enzymes (AChE and BuChE). The results showed that all the seventeen derivatives interact with the enzymes with high affinity and among them 7d and 7f possess the greatest ability to bind to AChE and BuChE, respectively.

Kinetics and Mechanism of the Gold-Catalyzed Hydroamination of 1,1-Dimethylallene with N-Methylaniline

The mechanism of the intermolecular hydroamination of 3-methylbuta-1,2-diene (1) with N-methylaniline (2) catalyzed by (IPr)AuOTf has been studied by employing a combination of kinetic analysis, deuterium labelling studies, and in situ spectral analysis of catalytically active mixtures. The results of these and additional experiments are consistent with a mechanism for hydroamination involving reversible, endergonic displacement of N-methylaniline from [(IPr)Au(NHMePh)]⁺ (4) by allene to form the cationic gold π-C1,C2-allene complex [(IPr)Au(η² -H₂ C=C=CMe₂ )]⁺ (I), which is in rapid, endergonic equilibrium with the regioisomeric π-C2,C3-allene complex [(IPr)Au(η² -Me₂ C=C=CH₂ )]⁺ (I'). Rapid and reversible outer-sphere addition of 2 to the terminal allene carbon atom of I' to form gold vinyl complex (IPr)Au[C(=CH₂ )CMe₂ NMePh] (II) is superimposed on the slower addition of 2 to the terminal allene carbon atom of I to form gold vinyl complex (IPr)Au[C(=CMe₂ )CH₂ NMePh] (III). Selective protodeauration of III releases N-methyl-N-(3-methylbut-2-en-1-yl)aniline (3 a) with regeneration of 4. At high conversion, gold vinyl complex II is competitively trapped by an (IPr)Au⁺ fragment to form the cationic bis(gold) vinyl complex {[(IPr)Au]₂ [C(=CH₂ )CMe₂ NMePh]}⁺ (6).

Cycloisomerization of π-Coupled Heteroatom Nucleophiles by Gold Catalysis: En Route to Regiochemically Defined Heterocycles

Since the dawn of millennium, catalytic gold chemistry is at the forefront to set off diverse organic reactions via unique activation of π-bonded molecules. Within this purview, cycloisomerization of heteroatom nucleophiles linked to a π-system is one of the well recognized chemistry for the construction of numerous heterocyclic cores. Though the rudimentary aspects of this transformation are reviewed by several groups in different timeline, a holistic view on regiochemistry of such reactions went largely overlooked. Hence, this account emphasizes the gold catalyzed regioselective cycloisomerization of structurally distinctive π-connected hetero-nucleophiles leading to different heterocycles documented in the last two decades. From an application perspective, this account also highlights those methodologies which find a role in the total synthesis of natural products. Wherever appropriate, mechanistic details and contributing factors for selectivity are also discussed.

The Increasing Value of Biomass: Moving From C6 Carbohydrates to Multifunctionalized Building Blocks via 5-(hydroxymethyl)furfural

Recent decades have been marked by enormous progress in the field of synthesis and chemistry of 5-(hydroxymethyl)furfural (HMF), an important platform chemical widely recognized as the "sleeping giant" of sustainable chemistry. This multifunctional furanic compound is viewed as a strong link for the transition from the current fossil-based industry to a sustainable one. However, the low chemical stability of HMF significantly undermines its synthetic potential. A possible solution to this problem is synthetic diversification of HMF by modifying it into more stable multifunctional building blocks for further synthetic purposes.

Gold-Catalyzed Addition of Carboxylic Acids to Alkynes and Allenes: Valuable Tools for Organic Synthesis

In this contribution, the application of gold-based catalysts in the hydrofunctionalization reactions of alkynes and allenes with carboxylic acids is comprehensively reviewed. Both intra- and intermolecular processes, leading respectively to lactones and linear unsaturated esters, are covered. In addition, cascade transformations involving the initial cycloisomerization of an alkynoic acid are also discussed.

2-Formylpyrrole natural products: origin, structural diversity, bioactivity and synthesis

2-Formylpyrroles constitute a large and growing family of bioactive Maillard reaction products found in food, traditional medicine and throughout nature.

Rapid and Effective Synthesis of α-Acyloxy-α-alkynyltrimethylsilanes

α-Alkynyl-α'-trimethylsilylhydrazones are readily oxidized into diazo compounds under simple experimental conditions. These stable diazo species can in turn react with a range of carboxylic acids via a protonation-nucleophilic substitution sequence, leading to valuable α-acyloxy-α-alkynyltrimethylsilanes. This procedure avoids the delicate preparation and manipulation of α-hydroxypropargyltrimethylsilanes.

Total Synthesis and Stereochemical Revision of the 2-Formylpyrrole Alkaloid Hemerocallisamine I

The first total synthesis of the 2-formylpyrrole alkaloid hemerocallisamine I is reported. The convergent synthesis features a key Maillard-type condensation of a complex amine derived from cis-4-hydroxy-l-proline with a dihydropyranone, to directly furnish the 2-formylpyrrole ring system. The absolute configuration of hemerocallisamine I has been revised on the basis of optical rotation data obtained for the synthesized compound.

Gold catalysis in total synthesis--an update

In this critical review, the strongly increasing amount of new applications of gold catalysis in total synthesis is summarised and, for the new developed methods, the mode of activation of the substrate by the gold catalyst is discussed (47 references).