Highly Efficient and Convenient Access to Phosphinates via CHCl₃‐Assisted Direct Phosphorylation between R₂P(O)H and ROH by Phosphonium Salt Catalysis

Abstract

A mild, efficient, convenient and scalable method to synthesize phosphinates via direct phosphorylation between R 2 P(O)H and ROH was developed. All aromatic substrates completed this transformation with excellent yields (up to 98 %), Compounds containing P-O bonds, such as phosphinates (R 2 P(O)OR), serve as important classes of ligands, catalysts, and synthetic intermediates in modern organic chemistry. As they are also widely present in pharmaceuticals and other valuable organic materials. [1] Accordingly, much attention has been dedicated to P-O bond formation for the construction of phosphinate compounds. Over the past decades, several typical routes reported relied on the addition of alcohols to sensitive phosphinic chlorides [R 2 P(O)Cl], [2] or on the esterification of phosphinic acids [R 2 P(O)OH], [3] including via the CCl 4 -mediated Atherton-Todd process. [4] In view of the need for more environmentally-friendly and atom-economical organic reactions, developing greener syntheses of phosphinate derivatives remains a highly desirable, albeit challenging task. [5] Over the past years, the transition metal or other reagent promoted oxidative phosphorylation reactions (Scheme 1a) have been extensively studied for constructing phosphinate compounds via a P-O bond formation process. [6] In 2014, Yang disclosed a copper-catalyzed phosphorylation reaction by employing excess DDQ as oxidant. [7] Later, Han reported the ironcatalyzed direct phosphorylation under oxidant-free conditions with high reaction temperature. [8] Meanwhile, the metal-free systems including Tf 2 O/H 2 O 2 and Ph 2 I + could also promote this transformation, yielding corresponding phosphinate products. [9,3b] Moreover, the C-H activation/phosphorylation [10] and other related strategies [11] were disclosed as efficient ways as well. Of note, among all reported approaches so far, either [a] Dr.Scheme 4. Proposed reaction mechanism.provided an efficient, scalable and convenient way to synthesize phosphinate derivatives in a highly reactive manner. Furthermore, no oxidant additives were needed for this phosphorylation reaction owing to the new activation mode of a carbene-involving process. Further investigation on the detailed mechanism and applications are in progress.

Access to S-Stereogenic Free Sulfoximines via Bifunctional Phosphonium Salt-Catalyzed Desymmetrization of Bisphenols

“…The cross-coupling reaction between P­(O)–H compounds and alcohols/amines, being henceforth referred to as the Atherton–Todd (A–T) reaction, represents a straightforward and economic approach for the functionalization of free OH/NH groups into P-containing motifs. , Consequently, substantial efforts have been devoted to this reaction over the past decade. However, the catalytic asymmetric variant of such a coupling reaction still remains elusive.…”

Using molecular straps to engineer conjugated porous polymer growth, chemical doping, and conductivity

“…Typically, the mono and diaryl oxidized phosphorous peaks appear between 0 and 30 ppm as shown previously in related compounds. 41,42 Incompletely reacted phosphorous trichloride can be oxidized by the moisture in the air or during the polymer reprecipitation in methanol and/or soxhlation with methanol. Therefore, the broad peak centered at ca.…”

Primary Amination of Ar2P(O)–H with (NH4)2CO3 as an Ammonia Source under Simple and Mild Conditions and Its Extension to the Construction of Various P–N or P–O Bonds

“…Until now, the direct nucleophilic substitution of moisture-sensitive phosphoryl halides with ammonia gas or aqueous ammonia represents the dominant procedure for the preparation of primary phosphinamides (Scheme a) . Afterward, pioneering Atherton–Todd reactions emerged as a partial solution which avoids the direct use of phosphoryl halides by generating them in situ from polyhaloalkanes (CHI 3 or CCl 4 ) and P­(O)–H reagents (Scheme b). ,, Nevertheless, as the most widely used amine sources, ammonia gas and aqueous ammonia are not perfect yet, due to their volatility and explosibility. Alternatively, ammonium salts feature bench stability, easy operation, and accessibility, but they are narrowly used in the nucleophilic substitution because of their weak nucleophilicity .…”