Palladium-Catalyzed Direct Decarbonylative Phosphorylation of Benzoic Acids with P(O)-H Compounds

Heteropolyacid-Catalyzed Phosphorylation of Secondary Aromatic Alcohols with H-Phosphine Oxides in DMC: A Simple Protocol for C-P Bond Formation

We successfully achieved the phosphorylation of secondary aromatic alcohols with H-phosphine oxides (less developed system) using phosphotungstic acid as a catalyst in dimethyl carbonate. The system was simple and environmentally friendly and showed better activity than traditional Lewis or Brønsted acids such as FeCl3, p-TsOH·H2O, etc., generating up to a 97% isolated yield. Control experiments indicated that the reaction did not occur through the radical pathway, and ethers and carbocation were the key intermediates in the pathway.

Palladium-Catalyzed Decarbonylative Sonogashira Alkynylation of Carboxylic-Phosphoric Anhydrides

We report the first palladium-catalyzed decarbonylative alkynylation of carboxylic-phosphoric anhydrides via highly selective C(O)-O bond cleavage. Carboxylic-phosphoric anhydrides are highly active carboxylic acid derivatives, which are generated through activating carboxylic acids using phosphates by esterification or direct dehydrogenative coupling with phosphites. Highly valuable internal alkynes have been generated by the present method, and the efficiency of this approach has been demonstrated through a wide substrate scope and excellent functional group tolerance.

Metal-free highly chemo-selective bisphosphorylation and deoxyphosphorylation of carboxylic acids

Carboxylic acids are readily available in both the natural and synthetic world. Their direct utilization for preparing organophosphorus compounds would greatly benefit the development of organophosphorus chemistry. In this manuscript, we describe a novel and practical phosphorylating reaction under transition metal-free reaction conditions that can selectively convert carboxylic acids into the P-C-O-P motif-containing compounds through bisphosphorylation, and the benzyl phosphorus compounds through deoxyphosphorylation. This strategy provides a new route for carboxylic acid conversion as the alkyl source, enabling highly efficient and practical synthesis of the corresponding value-added organophosphorus compounds with high chemo-selectivity and wide substrate scope, including the late modification of complex APIs (active pharmaceutical ingredients). Moreover, this reaction also indicates a new strategy for converting carboxylic acids into alkenes by coupling this work and the subsequent WHE reaction with ketones and aldehydes. We anticipate that this new mode of transforming carboxylic acids will find wide application in chemical synthesis.

A one-step base-free synthesis of N-arylamides via modified pivaloyl mixed anhydride mediated amide coupling

Pivalic anhydride is shown to be an effective reagent for direct amidation of carboxylic acids with N-alkyl anilines. The only by-product of this reaction is nontoxic pivalic acid, which can be easily removed by aqueous workup. The reactions are conducted under mild conditions and found to be compatible with a range of carboxylic acids, including aromatic, heterocyclic, acrylic, and aliphatic carboxylic acids and amino acids generating the desired amides in short reaction times.

Comprehensive Review on Synthesis, Properties, and Applications of Phosphorus (PIII, PIV, PV) Substituted Acenes with More Than Two Fused Benzene Rings

This comprehensive review, covering the years 1968-2022, is not only a retrospective investigation of a certain group of linearly fused aromatics, called acenes, but also a presentation of the current state of the knowledge on the synthesis, reactions, and applications of these compounds. Their characteristic feature is substitution of the aromatic system by one, two, or three organophosphorus groups, which determine their properties and applications. The (P^III, P^IV, P^V) phosphorus atom in organophosphorus groups is linked to the acene directly by a P-C_sp2 bond or indirectly through an oxygen atom by a P-O-C_sp2 bond.

Palladium-Catalyzed Direct Decarbonylative Cyanation of Aryl Carboxylic Acids

The direct transformation of aryl carboxylic acids to aryl nitrile compounds is an interesting topic because carboxylic acids are not only abundant in nature but are also inexpensive and stable. Here, the synthesis of a series of aryl nitriles by palladium-catalyzed decarbonylative cyanation of carboxylic acids without base has been achieved. The successful decarbonylative cyanation of drug molecules and Gram-scale reaction to verify the practicality and operability of this method are analyzed.

Palladium-Catalyzed Decarbonylative Cyanation of Carboxylic Acids with TMSCN

The direct decarbonylative cyanation of benzoic acids with TMSCN was achieved through palladium catalysis. By this strategy, a wide range of nitriles including those with functional groups was synthesized in good to high yields. Moreover, this reaction applied to modifying bioactive molecules such as adapalene, probenecid, telmisartan, and 3-methylflavone-8-carboxylic acid. These results demonstrate that this new reaction has potential synthetic value in organic synthesis.

Nickel-Catalyzed Decarbonylative Thioetherification of Carboxylic Acids with Thiols

A nickel-catalyzed decarbonylative thioetherification of carboxylic acids with thiols was developed. Under the reaction conditions, benzoic acids, cinnamic acids, and benzyl carboxylic acids coupled with various thiols including both aromatic and aliphatic ones produce the corresponding thioethers in up to 99% yields. Moreover, this reaction was applicable to the modification of bioactive molecules such as 3-methylflavone-8-carboxylic acid, probenecid, and flufenamic acid, and the synthesis of acaricide chlorbenside. These results well demonstrated the potential synthetic value of this new reaction in organic synthesis.

The concise synthesis and resolution of planar chiral [2.2]paracyclophane oxazolines by C-H activation

Planar chiral [2.2]paracyclophanes are resolved through the direct C–H arylation of enantiopure oxazolines, providing a convenient route to ligands and chiral materials. Preliminary results show that hydrolysis followed by decarboxylative phosphorylation leads to enantiopure [2.2]paracyclophane derivatives that are otherwise challenging to prepare.

Racemic bromo[2.2]paracyclophanes are directly transformed into enantiomerically pure planar chiral oxazolines in one step with simultaneous resolution of planar chirality.

Recent developments in decarboxylative C(aryl)-X bond formation from (hetero)aryl carboxylic acids

Decarboxylative coupling reactions using readily available (hetero)aryl carboxylic acids are a highly efficient approach for the formation of new C-C and C-X bonds. These decarboxylative coupling reactions eliminate CO2 as a by-product, resulting in a greener and environmentally more benign approach than conventional coupling reactions. In this review, we summarize the recent developments in ipso-decarboxylative C-X (X = O/N/halo/S/Se/P/CN) bond formations using (hetero)aryl carboxylic acids. Furthermore, we highlight the current limitations and future research opportunities of aryl-decarboxylative coupling reactions.

Palladium-Catalyzed Decarbonylative Sonogashira Coupling of Terminal Alkynes with Carboxylic Acids

A direct decarbonylative Sonogashira coupling of terminal alkynes with carboxylic acids was achieved through palladium catalysis. This reaction did not use overstoichiometric oxidants, thus overcoming the homocoupling issue of terminal alkynes. Under the reaction conditions, a wide range of carboxylic acids including those bioactive ones could couple readily with various terminal alkynes, thus providing a relative general method for preparing internal alkynes.

Tunable C–H arylation and acylation of azoles with carboxylic acids by Pd/Cu cooperative catalysis

Direct C–H arylation and acylation of azoles with carboxylic acids are achieved selectively through Pd/Cu cooperative catalysis: biaryls are generated selectively with dppp as ligand, while biaryl ketones are obtained with high selectivity using dpph or Ph₂PCy as ligand.

Phosphorylation of Carboxylic Acids and Their Derivatives with P(O)–H Compounds Forming P(O)–C Bonds

Herein, we highlight advances in the phosphorylation of readily available carboxylic acids and their derivatives forming synthetically important P(O)–sp3C, P(O)–sp2C, and P(O)–spC bonds, with an emphasis on the results demonstrated since 2010. This review examines the challenges associated with the use of this strategy for the synthesis of organophosphorus compounds and details advances in the design of catalytic systems that suppress these problems thus resulting in notable progress. Mechanistic details are discussed where available.

1 Introduction

2 Formation of P(O)–sp3C Bonds

3 Formation of P(O)–sp2C Bonds

4 Formation of P(O)–spC Bonds

5 Outlook and Conclusion

One-step synthesis of benzo[b]thiophenes by aryne reaction with alkynyl sulfides

An aryne reaction with alkynyl sulfides affording benzo[b]thiophenes is disclosed. A wide range of 3-substituted benzothiophenes were synthesized from easily available o-silylaryl triflates and alkynyl sulfides in a one-step intermolecular manner. The synthesis of diverse multisubstituted benzothiophene derivatives involving a pentacyclic compound was achieved by virtue of the good functional group tolerance and versatile C2 functionalizations.

Focusing on the Catal. of the Pd- and Ni-Catalyzed Hirao Reactions

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)₂-promoted cases are summarized, and it is concluded that the “(HOY₂P)₂Pd(0)” species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the “(HOY₂P)(−OY₂P)Ni(II)Cl⁻” form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations.

Phosphine Oxides from a Medicinal Chemist's Perspective: Physicochemical and in Vitro Parameters Relevant for Drug Discovery

Phosphine oxides and related phosphorus-containing functional groups such as phosphonates and phosphinates are established structural motifs that are still underrepresented in today's drug discovery projects, and only few examples can be found among approved drugs. In this account, the physicochemical and in vitro properties of phosphine oxides and related phosphorus-containing functional groups are reported and compared to more commonly used structural motifs in drug discovery. Furthermore, the impact on the physicochemical properties of a real drug scaffold is exemplified by a series of phosphorus-containing analogs of imatinib. We demonstrate that phosphine oxides are highly polar functional groups leading to high solubility and metabolic stability but occasionally at the cost of reduced permeability. We conclude that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist's toolbox.