Novel, Stereoselective and Stereospecific Synthesis of Allenylphosphonates and Related Compounds via Palladium-Catalyzed Propargylic Substitution

Copper-Catalyzed Asymmetric Cyanation of Propargylic Radicals via Direct Decarboxylation of Propargylic Carboxylic Acids

Chiral propargylic cyanides are often used as small-molecule feedstocks for the introduction of chiral centers into various valuable products and complex molecules. Here, we have developed a highly atom-economical strategy for the chiral copper complex-catalyzed synthesis of chiral propargylic cyanides. Propargylic radicals can be smoothly obtained by direct decarboxylation of the propargylic carboxylic acids without preactivation. The reactions show excellent selectivity and functional group compatibility. Gram-scale reaction and several conversion reactions from chiral propargylic cyanide have demonstrated the synthetic value of this strategy.

Nickel-catalyzed switchable 1,3-dienylation and enantioselective allenylation of phosphine oxides

The development of general catalytic methods for the regio- and stereoselective construction of phosphoryl derivatives from identical substrates remains a formidable challenge in organic synthesis. Enabled by the newly developed BDPP-type ligands, we disclosed a nickel-catalyzed allenylation of phosphine oxides rationally and predictably, allowing the construction of versatile chiral allenylphosphoryl derivatives with high enantiopurity (up to 94% e.e.). Alternatively, using an achiral phosphine ligand dcypbz under acidic conditions, we achieved a regiochemical switch of the 1,3-dienylation to afford functionalized phosphinoyl 1,3-butadienes (up to 93% yield). The salient features of this method include switchable reactivity, broad substrate scope, readily available feedstock, single-step preparation, and high asymmetric induction.

Catalytic Asymmetric Axially Chiral Allenyl C-P Bond Formation

Chiral organophosphorous compounds are very important in catalysis, organic syntheses, and medicinal chemistry. However, catalytic enantioselective protocols for the axially chiral allenyl phosphorus compounds have never been reported. Herein, a palladium-catalyzed enantioselective carbon-phosphorus bond formation reaction affording axially chiral allenyl phosphonates has been developed. The reaction enjoys high yields and ees accommodating a wide range of functional groups. Mechanistic studies have unveiled an overwhelming kinetic resolution process.

Silver(i)-catalyzed dehydrogenative cross-coupling of 2-aroylbenzofurans with phosphites

The silver(i)-catalyzed dehydrogenative cross-coupling reaction of 2-aroylbenzofurans with phosphites to afford 2-aroyl-3-phosphonylbenzofurans is reported.

Catalysis and regioselectivity in hydrofunctionalization reactions of unsaturated carbon bonds. Part III

The review addresses the possibility of obtaining Markovnikov and anti-Markovnikov isomers in the reactions of unsaturated hydrocarbons with organophosphorus and organosulfur compounds having P–H and S–H bonds using metal salts or complexes as catalysts.

The bibliography includes 247 references.

Stereoselective preparation of P,axial-stereogenic allenyl bisphosphine oxides via chirality-transfer

P,C-Stereogenic propargyl alcohols RC-3/SC-3' were prepared by the addition of (L)-menthyl-derived SPOs to propynals, which were converted to P,axial-stereogenic allenyl bisphosphine oxides. The chirality transfer was controlled by α-carbon via syn [2,3]-sigmatropic rearrangement. For SC-3' linking weak WDG on the alkynyl moiety, the chirality on the axis depended on stereogenic phosphorus.

Copper-Catalyzed Asymmetric Silylation of Propargyl Dichlorides: Access to Enantioenriched Functionalized Allenylsilanes

A copper‐catalyzed silylation of propargyl dichlorides was developed to access chloro‐substituted allenylsilanes under mild reaction conditions. Moreover, enantioenriched chloro‐substituted allenylsilanes can be synthesized in moderate to high yields and good enantioselectivities with this protocol.

Synthesis of multi-substituted allenes from organoalane reagents and propargyl esters by using a nickel catalyst

A highly efficient and simple route for the synthesis of multi-substituted allenes has been developed by a nickel catalyzed SN2' substitution reaction of propargyl esters with organic aluminium reagents under mild conditions, which gave the corresponding multi-substituted allenes in good to excellent yields (up to 92%) and high selectivities (up to 99%) at 60 °C for 6 h in THF. Aryls bearing electron-donating or electron-withdrawing groups in propargyl esters gave products in good yields. In addition, the multi-substituted allenes bearing a thienyl or a pyridyl group were obtained in 95-97% selectivities with isolated yields of 72-83%. Furthermore, the SN2' substitution reaction worked efficiently with propargyl carbonate compounds as well. On the basis of the experimental results, a possible catalytic cycle has been proposed.

Scope and advances in the catalytic propargylic substitution reaction

Nucleophilic displacement of the propargylic alcohol is one of the sought-after methods in the current scenario. The highly nucleophilic alkyne functional moiety along with its considerably acidic terminal hydrogen atom allows the propargylic unit to play a crucial role in organic synthesis by offering a handle for further synthetic transformations. Until 2000, the most fundamental propargylic substitution reaction was the Nicolas reaction, a multi-step transformation, developed in 1972, which involved cobalt as a stoichiometric promoter. Therefore, the direct catalytic substitution of propargylic alcohols was a highly desirable method for development. The pioneering work on the Ru-catalyzed propargylic substitution reaction in 2000 encouraged many researchers to develop several novel catalytic propargylic substitution reactions, which have made rapid progress since then. The purpose of this review is to emphasise the involvement of diverse types of Lewis acid, transition metal and Brønsted acid catalysts in the propargylic substitution reaction and provide an updated summary of the recent developments in this field. The selected examples presented here are the most significant and relevant ones and we believe that this will help the readers to comprehend the scope of the propargylic substitution reaction with diverse types of catalysts and will envisage the scientific community for the future developments in this field.

Direct nucleophilic displacement of the alpha-hydroxy of the propargylic alcohol is one of the sought-after methods in the current scenario. An updated summary of the recent developments in this field is presented here.

Intramolecular Chirality Transfer [2 + 2] Cycloadditions of Allenoates and Alkenes

Intramolecular chirality transfer [2 + 2] cycloaddition of enantiomerically enriched allenoates and alkenes is presented. The use of a chiral catalyst was found to be critical to achieve high levels of diastereoselectivity compared to use of an achiral catalyst. The method developed leads to highly substituted cyclobutanes that would be difficult to prepare by alternative methods.

Cu/Pd cooperatively catalyzed tandem C–N and C–P bond formation: access to phosphorated 2H-indazoles

An unprecedented Cu/Pd cooperatively catalyzed tandem C–N/C–P bond formation reaction for the synthesis of phosphorated 2H-indazoles has been developed.

Silver-catalyzed phosphonylation of unprotected propargylic alcohols for the synthesis of allenylphosphoryl compounds

A facile and efficient method for the synthesis of a variety of allenylphosphine oxides by silver-catalyzed phosphonylation of unprotected propargylic alcohols with P(O)H compounds has been established.

Elucidation of Mechanisms and Selectivities of Metal-Catalyzed Reactions using Quantum Chemical Methodology

Quantum chemical techniques today are indispensable for the detailed mechanistic understanding of catalytic reactions. The development of modern density functional theory approaches combined with the enormous growth in computer power have made it possible to treat quite large systems at a reasonable level of accuracy. Accordingly, quantum chemistry has been applied extensively to a wide variety of catalytic systems. A huge number of problems have been solved successfully, and vast amounts of chemical insights have been gained. In this Account, we summarize some of our recent work in this field. A number of examples concerned with transition metal-catalyzed reactions are selected, with emphasis on reactions with various kinds of selectivities. The discussed cases are (1) copper-catalyzed C-H bond amidation of indoles, (2) iridium-catalyzed C(sp(3))-H borylation of chlorosilanes, (3) vanadium-catalyzed Meyer-Schuster rearrangement and its combination with aldol- and Mannich-type additions, (4) palladium-catalyzed propargylic substitution with phosphorus nucleophiles, (5) rhodium-catalyzed 1:2 coupling of aldehydes and allenes, and finally (6) copper-catalyzed coupling of nitrones and alkynes to produce β-lactams (Kinugasa reaction). First, the methodology adopted in these studies is presented briefly. The electronic structure method in the great majority of these kinds of mechanistic investigations has for the last two decades been based on density functional theory. In the cases discussed here, mainly the B3LYP functional has been employed in conjunction with Grimme's empirical dispersion correction, which has been shown to improve the calculated energies significantly. The effect of the surrounding solvent is described by implicit solvation techniques, and the thermochemical corrections are included using the rigid-rotor harmonic oscillator approximation. The reviewed examples are chosen to illustrate the usefulness and versatility of the adopted methodology in solving complex problems and proposing new detailed reaction mechanisms that rationalize the experimental findings. For each of the considered reactions, a consistent mechanism is presented, the experimentally observed selectivities are reproduced, and their sources are identified. Reproducing selectivities requires high accuracy in computing relative transition state energies. As demonstrated by the results summarized in this Account, this accuracy is possible with the use of the presented methodology, benefiting of course from a large extent of cancellation of systematic errors. It is argued that as the employed models become larger, the number of rotamers and isomers that have to be considered for every stationary point increases and a careful assessment of their energies is therefore necessary in order to ensure that the lowest energy conformation is located. This issue constitutes a bottleneck of the investigation in some cases and is particularly important when analyzing selectivities, since small energy differences need to be reproduced.

A Pd complex of a NNN pincer ligand supported on γ-Fe2O3@SiO2 as the first magnetically recoverable heterogeneous catalyst for C–P bond forming reactions

A Pd complex of the NNN pincer ligand supported on γ-Fe₂O₃@SiO₂ was used as a new catalyst for a phosphonation reaction.

Spontaneous resolution upon crystallization of allenyl-bis-phosphine oxides

The first example of ‘spontaneous resolution by crystallization’ in allene chemistry, by means of crystal structures and solid state CD spectra of the R and S enantiomers, is presented.

Stereocontrol in Palladium-Catalyzed Propargylic Substitutions: Kinetic Resolution to give Enantioenriched 1,5-Enynes and Propargyl Acetates

Kinetic resolution during the catalytic allyl-propargyl cross-coupling with chiral starting materials can be accomplished with a chiral Palladium catalyst. These reactions offer ready access to enantiomerically enriched enyne products from simple readily available starting materials.