Vicinal All-Carbon Quaternary Stereocenter Construction with Trifluoromethyl Groups via Organocatalytic Asymmetric Cascade Michael/Michael Reaction

A thiourea organocatalyst efficiently promoted the asymmetric cascade Michael/Michael reactions between isatin-derived trifluoromethylacrylate and α-alkylidene succinimide, resulting in high yields of spirooxindole derivatives. These compounds exhibit vicinal all-carbon quaternary stereocenters and bear a trifluoromethyl group, with excellent enantioselectivities reaching up to 99 % ee. This work represents the first successful organocatalyst application for the direct construction of vicinal all-carbon quaternary stereocenters, featuring a trifluoromethyl group.

Recent Developments in Intermolecular Cross-Rauhut-Currier Reactions

Intermolecular cross Rauhut-Currier reactions have gained much importance in recent years. It has proved its importance through procedures involving various catalysts and resulting in complex structures with good regio- as well as stereo- selectivity. This review highlights the recent developments of these reactions, published in current years, involving both achiral and chiral catalysts to give products, having various utilities. In addition, the detailed mechanistic studies of the above-mentioned reactions are also presented.

Construction of CF3-Functionalized Fully Substituted Benzonitriles through Rauhut-Currier Reaction Initiated [3 + 3] Benzannulation

Though numerous cyanation reactions have been developed for the synthesis of benzonitriles, the construction of valuable fully substituted benzonitriles is still a challenging task. Herein, we reported a tertiary amine-catalyzed [3 + 3]-benzannulation for the green synthesis of CF₃-functionalized fully substituted benzonitriles. This strategy features exclusive chemoselectivity, high atom-economy, and good step-economy with environment-friendly reagents and mild conditions. Unique triphenyl-substituted dicyanobenzoate products could be rapidly constructed using this method. The practicality and reliability of this reaction were proved by the successful scale-up synthesis. A mechanistic study indicates that the [3 + 3]-benzannulation was initiated by an intermolecular Rauhut-Currier reaction.

Chemoselective synthesis of multifunctional ferrocene-containing derivatives by the cross Rauhut-Currier reaction

A simple protocol has been developed for the chemoselective synthesis of ferrocene-containing Rauhut-Currier adducts from 1-ferrocenyl-2-nitroethene and vinyl ketones using 20 mol% of triphenylphosphine. Multifunctional ferrocene derivatives were obtained in moderate to high yields (51-92%) by the coupling between the α-position of vinyl ketones and the β-position of the nitroalkene. The study of the Rauhut-Currier reaction under the described conditions showed that the strong electron-donating group at the β-position of nitroalkenes plays a significant role in the reaction outcome due to prevention of polymerization and stabilization of the zwitterionic intermediate. Additionally, a preparative synthesis of 4-ferrocenyl-3-methylene-5-nitropentan-2-one was carried out and its synthetic transformations showed easy conversion to other useful building blocks.

DMAP Catalyzed Domino Rauhut-Currier Cyclization Reaction between Alkylidene Pyrazolones and Nitro-olefins: Access to Tetrahydropyrano[2,3-c]pyrazoles

Herein, we employ unsaturated pyrazolones in the Rauhut-Currier reaction for the first time. A domino Rauhut-Currier cyclization reaction has been developed between unsaturated pyrazolones and nitro-olefins. The trisubstituted tetrahydropyrano[2,3-c]pyrazoles were obtained in moderate to high yields with excellent diastereoselectivities. A few applications including a synthesis of disubstituted tetrahydropyrano[2,3-c]pyrazole have been demonstrated. A preliminary catalytic asymmetric version of this process was also studied with chiral DMAP catalysts.

Connecting and Analyzing Enantioselective Bifunctional Hydrogen Bond Donor Catalysis Using Data Science Tools

The generalization of related asymmetric processes in organocatalyzed reactions is an ongoing challenge due to subtle, noncovalent interactions that drive selectivity. The lack of transferability is often met with a largely empirical approach to optimizing catalyst structure and reaction conditions. This has led to the development of diverse structural catalyst motifs and inspired unique design principles in this field. Bifunctional hydrogen bond donor (HBD) catalysis exemplifies this in which a broad collection of enantioselective transformations has been successfully developed. Herein, we describe the use of data science methods to connect catalyst and substrate structural features of an array of reported enantioselective bifunctional HBD catalysis through an iterative statistical modeling process. The computational parameters used to build the correlations are mechanism-specific based on the proposed transition states, which allows for analysis into the noncovalent interactions responsible for asymmetric induction. The resulting statistical models also allow for extrapolation to out-of-sample examples to provide a prediction platform that can be used for future applications of bifunctional hydrogen bond donor catalysis. Finally, this multireaction workflow presents an opportunity to build statistical models unifying various modes of activation relevant to asymmetric organocatalysis.

Organophosphorus chemistry based on elemental phosphorus: advances and horizons

The results of studies on the application of elemental phosphorus for the synthesis of important organophosphorus compounds are surveyed and summarized. Currently, this trend represents a synthetically, environmentally and technologically attractive alternative to classical organophosphorus chemistry based on toxic and corrosive phosphorus chlorides. Direct phosphination and phosphinylation of organic compounds with elemental phosphorus (discussed in the first part of the review) basically extend the range of available phosphines, phosphine chalcogenides and phosphinic acids and provides further development of their synthetic potential (discussed in the second part of the review). It is shown that the breakthrough in this area is largely due to the discovery of reactions of elemental phosphorus (white and red) with various electrophiles in superbasic suspensions and emulsions derived from alkali metal hydroxides and to the development of electrochemical, electrocatalytic and catalytic activation of white phosphorus.

The bibliography includes 299 references.

Synthesis of polysubstituted arenes through organocatalytic benzannulation

Polysubstituted arenes serve as ubiquitous structural cores of aromatic compounds with significant applications in chemistry, biological science, and materials science. Among all the synthetic approaches toward these highly functionalized arenes, organocatalytic benzannulation represents one of the most efficient and versatile transformations in the assembly of structurally diverse arene architectures under mild conditions with exceptional chemo-, regio- or stereoselectivities. Thus, the development of new benzannulation reactions through organocatalysis has attracted much attention in the past ten years. This review systemically presents recent advances in the organocatalytic benzannulation strategies, categorized as follows: (1) Brønsted acid-catalysis, (2) secondary amine catalysis, (3) primary amine catalysis, (4) tertiary amine catalysis, (5) tertiary phosphine catalysis, and (6) N-heterocyclic carbene catalysis. Each part is further classified into several types according to the number of carbon atoms contributed by different synthons participating in the cyclization reaction. The reaction mechanisms involved in different benzannulation strategies were highlighted.

Organocatalytic benzannulation represents one of the most efficient transformations for assembling polysubstituted arenes, this review presents recent advances in organocatalytic benzannulation strategies to construct functionalized benzenes.

Substrate-directed chemo- and regioselective synthesis of polyfunctionalized trifluoromethylarenes via organocatalytic benzannulation

Highly chemo- and regioselective substrate-directed benzannulation of trisubstituted CF₃-alkenes and 2-benzylidenemalononitriles or 2-nitroallylic acetates has been achieved via Michael-initiated [4 + 2] or Rauhut–Currier-initiated [3 + 3] annulation.

Phosphine-catalysed asymmetric dearomative formal [4+2] cycloadditions of 3-benzofuranyl vinyl ketones

An asymmetric dearomative formal [4+2] cycloaddition reaction of 3-benzofuranyl vinyl ketones and 3-olefinic (7-aza)oxindoles is explored which is catalysed by chiral phosphines.

Amine-catalyzed and functional group-controlled chemo- and regioselective synthesis of multi-functionalized CF3-benzene via a metal-free process

A novel strategy for the synthesis of CF₃-containing multi-substituted benzenes with high chemo- and regioselectivities under metal-free and air-tolerant conditions was established.

Applications of N′-monofunctionalised TsDPEN derivatives in asymmetric catalysis

N′-Monoalkylated or N′-mono(thio)acylated(N-sulfonyl)-1,2-diphenylethylene-1,2-diamine (TsDPEN) derivatives are have found extensive applications in asymmetric catalysis of a wide range of synthetic applications.