Synthesis of biaryls by intramolecular radical transfer in phosphinates

Experimental study on the microreactor-assisted synthesis of phosphinic chlorides with varying steric hindrance

An efficient and catalyst-free method for the preparation of optically active and racemic mono-substituted t-butyl phosphinic chlorides ^tBuRP(O)Cl under flow conditions was reported.

Selective P-C(sp3 ) Bond Cleavage and Radical Alkynylation of α-Phosphorus Alcohols by Photoredox Catalysis

Herein the first P-C(sp³ ) bond cleavage and radical alkynylation of α-phosphorus alcohols to construct phosphonoalkynes is reported. The phosphorus radical is generated upon P-C bond cleavage reaction via the alkoxyl radical through photoredox catalysis with cyclic iodine(III) reagents. Various arylphosphinoyl-, alkylphosphinoyl-, phosphonate-, and phosphonic amide alcohols serve as radical phosphorus precursors to construct phosphonoalkynes for the first time.

Cross-coupling of sulfonic acid derivatives via aryl-radical transfer (ART) using TTMSS or photoredox

The intramolecular cross-coupling of sulfonic acid derivatives occurs in the presence of tris(trimethylsilyl)silane (TTMSS) at room temperature and in air to form biaryl compounds. A photoredox-catalyzed procedure is also described. These protocols provide mild and convenient alternatives to standard tin-mediated reactions.

Iron-catalyzed clean dehydrogenative coupling of alcohols with P(O)–H compounds: a new protocol for ROH phosphorylation

An efficient oxygen–phosphoryl bond-forming reactionviairon-catalyzed cross dehydrogenative coupling has been developed. The reaction proceeds efficiently under oxidant- and halide-free conditions with H₂liberation, and represents a straightforward method to prepare organophosphoryl compounds from alcohols and P(O)–H compounds.

Polyphosphorylated triphenylenes: synthesis, crystal structure, and selective catechol recognition

Designed as a multivalent hydrogen bond acceptor, new receptors, Discopus 1a,b, were built from a triphenylene core surrounded by six (diaryl)phosphinate groups. An efficient synthesis was developed to prepare these elaborated structures in a high overall yield. The X-ray structure of receptor 1b showed strong cooperative hydrogen bonds with two water molecules and intermolecular CH-pi contacts. In chloroform, Discopus 1a,b displayed recognition properties toward dihydroxybenzenes, selectively forming complexes with catechol derivatives 4a-c in a 1:2 (host:guest) stoichiometry. According to NMR and microcalorimetry titrations, association constants were found in the 30-2837 M(-1) range, which were larger than those reported for curvated catechol receptors (14-120 M(-1)). Interestingly, Discopus present two distinct catechol binding sites. Weak hydrogen bonding between host phosphinates and guest hydroxyl groups was shown by infrared spectroscopy and (31)P NMR. Molecular dynamics simulations and recognition experiments suggested that a stronger hydrogen bond assisted by a pi-interaction between the Discopus core and one catechol molecule could exist within the 1:2 complex.

Recent advances in the use of phosphorus-centered radicals in organic chemistry

This tutorial review aims at presenting recent contributions dealing with organic chemistry of organophosphorus radicals. The first part briefly lays out the physical organic background of such intermediates. In a second part the use of organophosphorus radicals possessing a P-H bond that can undergo homolytic cleavage as alternative mediators is detailed. The third part is focused on radical additions of phosphorus-centered radicals to unsaturated compounds, an old reaction that is being rejuvenated. Lastly, radical eliminations of phosphorus-centered radical are introduced in the fourth part. Most of the latter are relatively novel reactions, and have never been reviewed previously.

β Elimination of a phosphonate group from an alkoxyl radical — Intramolecular acylation using acylphosphonate derivatives as carbonyl group acceptors

The possibility of β elimination of a phosphonate group in radical reactions was studied. The facile β elimination of the phosphonate group from an alkoxyl radical was observed for the first time, whereas the β elimination of the phosphonate group from an aminyl and an alkyl radical did not occur. On the basis of our findings, the use of an acylphosphonate as a carbonyl group radical acceptor was investigated. Radical cyclization of the acylphosphonate in the presence of hexamethylditin in benzene at 300 nm for 2 h gave a cyclopentanone or a cyclohexanone derivative in good yield without the formation of a direct reduction product. The reaction can be carried out in the presence of a catalytic amount of hexamethylditin (0.2 equiv.) under similar conditions. In addition, an alkyl phosphonothiolformate group can act as an alkylthiocarbonyl group equivalent radical acceptor, providing ready access to a thiolactone synthesis.Key words: radical, β elimination, acylation, cyclization, acylphosphonate.

Beta-elimination of a phosphonate group from an alkoxy radical: an intramolecular acylation approach using an acylphosphonate as a carbonyl group acceptor

On the basis of facile beta-elimination of a phosphonate group from an alkoxy radical, intramolecular acylation reaction has been developed, in which an acylphosphonate is used as an excellent carbonyl group radical acceptor.