Rh-Catalyzed Regio- and Enantioselective Allylic Phosphinylation

Abstract

Transition-metal-catalyzed branched and enantioselective allylic substitution of monosubstituted precursors with carbon, nitrogen, oxygen, sulfur, and fluoride nucleophiles has been well-established. However, such a selective carbon–phosphorus bond formation has not been realized probably due to the catalyst deactivation by the strong coordinating nature of phosphinylating reagents. Herein, we report a Rh-catalyzed highly regio- and enantioselective synthesis of allylic phosphine oxides in the presence of a chiral bisoxazoline-phosphine ligand. The application of α-hydroxylalkyl­phosphine oxides to keep the low concentration of the secondary phosphine oxides is essential for the high yields. The addition of diphenyl phosphoric acid was found to not only activate allylic alcohols but also accelerate the carbon–phosphorus bond formation.

Secondary Phosphine Sulfide‐Enabled Iridium‐Catalyzed Asymmetric Allylic Substitution

“…31 P NMR monitoring experiments indicated the ligand displacement occurred within 20 min with 2 a′ as the nucleophiles (See Supporting Information for more details). The pre‐protected phosphinated reagent 2 a′′ reported by Li group, [10] was also explored with no conversion (entry 3). Screening different backbone‐derived P‐olefin ligands ( L2 to L3 ) showed that L1 provided the best stereoselectivity (entries 4, 5).…”

Multimetallic Pd- and Ni-catalyzed C(sp2)–P cross-coupling under aqueous micellar conditions

“…26,27 However, current C(sp 2 )–P cross-coupling methods are limited by (1) high catalyst loadings (often 10 mol %) and, in some cases, alternative procedures (slow addition of H -phosphonate) 28 or phosphorus precursors ( e.g. , masked H -phosphonates) 29 required to overcome the inhibitory effects of phosphorus nucleophiles on metal catalysts given their strong coordination properties, (2) catalytic transfer hydrogenation, whereby (hetero)aryl halides are converted into (hetero)arenes due to the undesired reducing properties of H–P compounds, 30,31 (3) heating at high temperatures (often above 100 °C) to facilitate the C(sp 2 )–P bond-forming reductive elimination step, rendering the reactions potentially incompatible with complex substrates bearing sensitive functional groups, and (4) aprotic polar solvents, such as N , N -dimethylformamide (DMF), 24,32 which is classified as toxic and hazardous 33 and its use has been restricted by the European Commission. 34 Further exacerbating these problems, state-of-the-art C(sp 2 )–P cross-coupling methods fail to meet increasing demands for environmentally responsible chemical processes with low energy costs and loadings of precious transition metal catalysts in environmentally benign solvents ( e.g.…”

Tridentate Sulfoxide-N-olefin Hybrid Ligands in Rhodium-Catalyzed Asymmetric Allylic Substitution

“…Based on a detailed mechanistic study, Breit proposed that the Rh σ-allyl complex is easily isomerized to the thermal dynamic stable chiral Rh-π-allyl complex in the presence of chiral bidentate ligand, accounting for the asymmetric transformation. Very recently, Li developed a Rh-catalyzed asymmetric allylic alkylation (AAA) reaction with a N , P , N -tridentate ligand ( L6 ) to further expand the scope of electrophiles and nucleophiles (Scheme b). It indicated that the third coordination is crucial to increase the oxidative addition ability of Rh complex to react with allylic substrates .…”