Microwave-assisted synthesis of α-aminophosphonates with sterically demanding α-aryl substituents

Abstract

A series of N-benzhydryl protected α-aminophosphonates with α-phenyl, α-(1-naphtyl), α-(9-anthryl) or α-(1-pyrenyl) substituents was synthesized by the Kabachnik–Fields condensation of diphenylmethylamine (benzhydrylamine), the corresponding aryl aldehyde and a dialkyl phosphite under MW irradiation. X-ray studies performed at low temperatures for a few of these α-aminophosphonates confirmed the presence of unusually short intramolecular C_α–H^δ+ ··· ^δ+H–C_peri contacts.     

Palladium-catalyzed homo-coupling of boronic acids with supported reagents in supercritical carbon dioxide

Palladium-catalyzed homo-coupling of arylboronic acids could proceed smoothly with a commercially available resin functionlised by phosphino or amino group as the ligand in supercritical carbon dioxide thereby offering a simple and efficient protocol for the synthesis of symmetrical bi-aryl molecules and their higher homologues.     

Synthesis of β-heteroaryl carbonyl compounds via direct cross-coupling of allyl alcohols with heteroaryl boronic acids under cooperative bimetallic catalysis

The eco-friendly cooperative Cu/Pd-catalyzed oxidative Heck reaction of allyl alcohols with heteroaryl boronic acids under air was described. The ready availability of starting materials and the mild reaction conditions made this protocol a safe and operationally convenient strategy for the efficient synthesis of β-heteroaryl carbonyl compounds.     

Suzuki-Miyaura cross-coupling of α-phosphoryloxy enol ethers with arylboronic acids

The Suzuki-Miyaura cross-coupling reaction of cyclic ketene acetal phosphates with arylboronic acids was found to be a convenient and highly efficient method for the construction of aryl vinyl ethers. A wide variety of differentially substituted electron-poor and electron-rich arylboronic acids smoothly underwent the coupling process to provide the desired dihydropyrans in moderate to excellent yields.     

Palladium-catalyzed desulfitative addition of sodium sulfinates with α,β-unsaturated carbonyl compounds

A palladium-catalyzed desulfitative conjugate addition of sodium sulfinates with α,β-unsaturated carbonyl compounds is described. The reaction showed very good selectivity and tolerated a wide range of functionalities under an atmosphere of argon.     

Silver-catalyzed decarboxylative cross-coupling of α-keto acids with alkenes giving approach to chalcones

A silver-catalyzed decarboxylative cross-coupling of α-keto acids with alkenes is reported. The method, with a wide range of substrate tolerance and mild operational conditions, can produce various chalcone derivatives in moderate to high yields from easily available starting materials.     

Pd-catalyzed enantioselective C–H arylation of phosphinamides with boronic acids for the synthesis of P-stereogenic compounds

A Pd-catalyzed enantioselective C–H arylation of phosphinamides with aryl boronic acids is presented. With readily affordable amino acid derivatives as chiral ligands, the reaction proceeded efficiently to afford the P-stereogenic phosphinamides in up to 75% yield and with 99% ee under mild conditions. Most importantly, the reaction could be performed on a large scale for various substrates. This method provides an alternative and reliable way for accessing P-stereogenic phosphinamides.     

Novel α-arylnitriles synthesis via Ni-catalyzed cross-coupling of α-bromonitriles with arylboronic acids under mild conditions

An applicable and easy-handling Ni-catalyst can be used to promote direct arylation of α-bromonitriles with various arylboronic acids to construct α-arylnitriles under mild conditions. The methodology tolerates β-hydrogens and functional groups in the substrates.     

The synthetic protocol for α-bromocarbonyl compounds via brominations

α-Bromocarbonyl compound easily generates α-radicals in the presence of a proper initiator, such as copper salt. Recently, tertiary-alkylation reaction using α-bromocarbonyl compound as a tertiary alkyl source is recognized as one of the most important alkylation reactions. The reactions using α-bromocarbonyl compound are increasing, whereas synthetic methods for various functionalized α-bromocarbonyl compounds are not summarized. Generally, α-bromocarbonyl compounds can be synthesized from the corresponding carboxylic acids via α-bromo acid bromide, but the brominations of carboxylic acids are sometimes problematic. In this paper, we will report some technical information for a bromination and synthetic examples of representative α-bromocarbonyl compounds.     

Preparation of α-oxygenated ketones by the dioxygenation of alkenyl boronic acids

Two in two: Dioxygenation of alkenyl boronic acids has been achieved with N-hydroxyphthalimide. The two-step process involves etherification of an alkenyl boronic acid with N-hydroxyphthalimide followed by a [3,3] rearrangement. The dioxygenated product can then be hydrolyzed to form either the corresponding α-hydroxy ketone or the α-benzoyloxy ketone.     

Palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols to γ,δ-unsaturated ketones

In this communication, a palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols has been developed. With Mo(CO)₆ as the CO source, γ,δ-unsaturated ketones were isolated in good yields. The release of CO₂ was confirmed as well.     

Palladium-catalyzed allylation of α-isocyanocarboxylates

α-Isocyanocarboxylates underwent palladium-catalyzed allylation with allylic acetates, in which π-allylpalladium(II) intermediate was involved. The catalytic allylation of methyl α-isocyano(phenyl)acetate using an optically active ferrocenylphosphine ligand caused an asymmetric induction of up to 39% ee.     

Salts of α-cyanoacrylic acid with sterically hindered tertiary amines

Syntheses are reported for representatives of a new class of derivatives of -cyanoacrylic acid, namely, its salts with brucine, tert-butyldimethylamine, and diisopropylmethylamine.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 212–214, January, 1992.     

Pd(II)-catalyzed decarboxylative cross-coupling of potassium aryltrifluoroborates with α-oxocarboxylic acids at room temperature

A novel Pd-catalyzed decarboxylative cross-coupling of potassium aryltrifluoroborates with α-oxocarboxylic acids is performed at room temperature. This reaction provides an efficient access to aryl ketones under mild conditions.     

Copper-catalyzed chemoselective cross-coupling reaction of thioamides and α-diazocarbonyl compounds: Synthesis of enaminones

The development of operationally simple and cost-effective methods for CC bond formation reactions are highly important in pharmaceutical, agrochemical and material research. In this article we describe the first copper-catalyzed cross-coupling reaction of thioamides with acceptor/acceptor-substituted and acceptor-only substituted α-diazocarbonyl compounds to yield enaminones. The reaction shows broad substrate scope in terms of thioamides and diazocarbonyl compounds. Primary, secondary and tertiary thioamides all give enanminones when reacted with α-diazodiesters, α-diazoketoesters, α-diazodiketones, α-diazoketoamides, α-diazoesteramides, α-diazoketosulfones and α-diazomonoketones.     

Palladium-catalyzed Negishi α-arylation of alkylsulfones

A general, mild catalytic system for α-monoarylation of various alkyl sulfones is described that utilizes palladium-catalyzed Negishi cross-coupling approach.     

Synthesis of polysubstituted isoquinolines through cross-coupling reactions with α-alkoxytosylhydrazones

A Pd-catalyzed cross-coupling reaction of α-alkoxytosylhydrazones with sulfonates derived from salicyl aldehydes gives rise to protected 1,5-dicarbonyl compounds. Treatment with ammonium hydroxide readily transforms these alkenes into isoquinolines with diverse substitution patterns at positions 3 and 4. In a similar way, the employment of o-cyanononaflates in the coupling reaction, followed by treatment with an organometallic, provides isoquinolines that incorporate substitution also at position 1. The combination of both approaches represents a versatile method for the preparation of isoquinolines substituted at any position of the heterocyclic ring.     

Synthesis of 3-acylindoles via decarboxylative cross-coupling reaction of free(N–H) indoles with α-oxocarboxylic acids

A convenient and general method for acylation of free(N–H) indoles via palladium-catalyzed decarboxylative cross-coupling reaction was developed. This process provided a useful method for the preparation of diverse 3-acylindoles in high yields utilizing a reaction with readily accessible reactants under mild conditions.