Phosphine-Catalyzed Intermolecular Dienylation of Alkynoate with para-Quinone Methides

Phosphine-catalyzed reaction of cyclopropenones with water: divergent synthesis of highly functionalized γ-butenolides, trisubstituted α,β-unsaturated acids and anhydride

The reaction between cyclopropenones and water catalyzed by different phosphines has been thoroughly investigated. Under the catalysis of trimethylphosphine, highly functionalized γ-butenolides were successfully synthesized from the simple starting material, cyclopropenones, and water in 35%-81% yields with excellent diastereoselectivities. Under the catalysis of triphenylphosphine, cyclopropenones were transferred to trisubstituted α,β-unsaturated acids with sufficient water in 78%-99% yields, while α,β-unsaturated acid anhydrides were obtained with trace water.

Conjugated 1,8 and 1,6 Addition of Bis-Trimethylsilylketene Acetal to Activated p-Quinone Methides via Trifluoromethanesulfonic Anhydride

In this work, we studied the conjugated additions of bis-trimethylsilylacetalketene acetals (bis-TMSKA) to para-quinone methides (p-QMs), which are one of the most explored molecules for the study of conjugated additions and gained significant attention in organic chemistry due to their versatile reactivity, particularly in Michael addition reactions. In this study, trifluoromethanesulfonic anhydride (Tf2O) was used as an activating agent for p-QMs, aiming to achieve 1,6-Michael addition products and the least reported 1,8-Michael addition with pyridine substituents. The reactivity of p-QMs derived from pyridine demonstrated distinct reaction pathways, leading to the formation of δ and γ lactones. The investigation also involved synthesizing a 1-indanone derived from the carboxylic acids obtained from the 1,6-addition.

Phosphine-Catalyzed γ'-Carbon 1,6-Conjugate Addition of α-Succinimide Substituted Allenoates with Para-Quinone Methides: Synthesis of 4-Diarylmethylated 3,4-Disubstituted Maleimides

In this paper, an interesting γ'-carbon 1,6-conjugate addition for phosphine-catalyzed α-succinimide substituted allenoates has been disclosed. A wide array of substrates was found to participate in the reaction, resulting in the production of diverse 4-diarylmethylated 3,4-disubstituted maleimides with satisfactory to outstanding yields. Furthermore, a plausible mechanism for the reaction was proposed by the investigators.

One-Step Protocol for the Synthesis of Cyanoacrylates Promoted by Elemental Sulfur from p-Quinone Methides and Cyanoacetates under Basic Conditions

Cyanoacrylates have a wide range of biological activities and are extensively applied in production and daily life. Classic synthetic routes to cyanoacrylates have many limitations. Herein, we demonstrate an elemental sulfur-promoted method for the synthesis of β,β-diaryl cyanoacrylates by a tandem 1,6-Michael addition/oxidation/elimination process from p-QMs and cyanoacetates under optimal conditions. The effective protocol has good substrate scopes and yields, and the ratio of inseparable E/Z isomers of cyanoacrylates is also determined by 1HNMR.

Phosphine-catalysed transformations of ortho- and para-quinone methides

Organocatalytic methodologies for the derivatization of o-QM, p-QM and the analogous aza-QM have been recently developed and involve different catalytic systems such as phosphoric acids, thioureas, squaramides, NHC carbenes or chiral ammonium salts. Besides, phosphines, commonly used as ligands in metal-catalysed reactions, can be also used as organocatalysts. In this case, they are mainly involved as nucleophilic catalysts in reactions such as the Rauhut-Currier (RC) reaction. In this review, an analysis of the recent developments in racemic and enantioselective phosphine-catalysed transformations of o-QM, p-QM and aza-o-QM has been carried out.

DMSO-promoted direct δ-selective arylation of p-quinone methenylpiperidine bearinides to generate fuchsones under metal-free conditions by employing p-QMs themselves or substituted phenols as aryl sources

Fuchsones have wide applications in modern society. Present methods for generating fuchsones have many disadvantages and there are significant limitations for further exploration of fuchsone applications. Herein, we describe a DMSO-promoted direct δ-selective arylation of p-QMs to synthesize symmetrical and unsymmetrical fuchsones under metal-free conditions by employing p-QMs themselves or substituted phenols as aryl sources. As unprecedented methods, these novel strategies present a great advantage and significance for further exploration of fuchsones and the development of new applications.

Catalytic Dienylation: An Emergent Strategy for the Stereoselective Construction of Conjugated Dienes and Polyenes

Stereoselective construction of conjugated dienes and polyenes has remained an enduring synthetic problem, due to the central roles they play in natural product synthesis, methodology, and medicine. This review focuses on the recent developments in dienylation as an emerging strategy for the direct installation of unsaturated four carbon atom units of conjugated π-systems, outlining the regio- and stereoselectivity, as well as the synthetic scope of reactions with various dienylating reagents and the mechanistic implications of the catalytic cross-coupling processes that are used to enable dienylation.

Titanium-Mediated aza-Nazarov Annulation for the Synthesis of N-Fused Tricycles: A General Method to Access Lamellarin Analogues

Fused heterocycles with nitrogen incorporation are of particular bioactive use and high importance in many research fields, especially isoquinoline-based [6/6/5] tricycles. Here, we report a unique strategy to access multifunctional N-fused tricycles from α,β-unsaturated isoquinoline ketone and sulfonamide under mild reaction conditions. The methodology features wide substrate tolerance, and a set of N-fused heteroarenes including quinoline, phthalazine, quinazoline, quinoxaline, and benzothiazole cores are furnished efficiently. Moreover, the protocol is easy to scale up to synthesize lamellarin analogues, and the amide group of the product is also easy to transfer to other functional groups.

Asymmetric cross Rauhut–Currier reactions of vinyl ketones with carbonyl para-quinone methides via phosphine catalysis

Novel cross Rauhut–Currier reactions, involving chiral phosphine catalysis, between vinyl ketones and terminal-carbonyl-substituted para-quinone methides are presented.