Pallado-catalysed hydrophosphination of alkynes: access to enantio-enriched P-stereogenic vinyl phosphine–boranes

Abstract

Preliminary results dealing with the synthesis of non-racemic P-stereogenic vinylphosphine-boranes by hydrophosphination of alkynes in the presence of a chiral catalyst are reported.

Mechanistic Insights into the Palladium‐Catalysed Asymmetric Phosphination of Cyclohexenyl Triflate

“…[20] The extra isomer 5min appeared to be a conformational isomer, which arose from slow rotation about the Pd-C bond on the NMR time scale. Similar behaviour was reported in the related Pt(DIOP)(o-An)(I) [21] and [Pd(DUPHOS)(o-An)-{PPhMe(BH 3 )}] complexes. [11] Table 2. 31 P{H} NMR spectroscopic data for 5 at -30°C.…”

“…[1] A promising new approach for their synthesis is asymmetric catalysis. Although a few examples have been recently reported in the literature through the use of catalytic hydrophosphination of alkynes [3] and C-P cross-coupling reaction of an alkenyl triflate, [4] the enantioselectivity reached and/or the scope of the reactions are too modest to envision preparing efficiently P-chirogenic tertiary phosphanes through these methodologies. Information on the mechanism and the factors, which affect the enantioselectivity of these reactions, would certainly be helpful to To get insights into the origin of the enantioselection, we embarked in a study aiming at characterizing likely intermediates involved in the different steps of the putative catalytic cycle by using 31 P NMR spectroscopy.…”

Recent Advances in Metal-Catalyzed C–P Bond Formation

“…Although no mechanism was proposed, the Pd(Me-DuPhos)-catalyzed asymmetric hydrophosphination of an alkyne with a phosphine-borane under kinetic resolution conditions (Scheme 6) presumably involves similar insertion and reductive elimination steps [14].…”

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

“…[35][36][37][38] Other alternative methods include the NHC-catalyzed desymmetrization of bisphenolic phosphinates, 39 the metal-catalyzed asymmetric cross-coupling of phosphines or phosphine oxides, [40][41][42][43][44][45] hydrophosphination of olefins, 46 addition reactions of phosphorus nucleophiles, 47,48 and olefin metathesis of divinyl phosphinates. 49 Despite these important advances, the development of general and practical methods for the efficient and versatile synthesis of P-stereogenic compounds remains a challenge.…”