A theory-driven synthesis of symmetric and unsymmetric 1,2-bis(diphenylphosphino)ethane analogues via radical difunctionalization of ethylene

Abstract

Abstract1,2-Bis(diphenylphosphino)ethane (DPPE) and its synthetic analogues are important structural motifs in organic synthesis, particularly as diphosphine ligands with a C2-alkyl-linker chain. Since DPPE is known to bind to many metal centers in a bidentate fashion to stabilize the corresponding metal complex via the chelation effect originating from its entropic advantage over monodentate ligands, it is often used in transition-metal-catalyzed transformations. Symmetric DPPE derivatives (Ar12P−CH2−CH2−PAr12) are well-known and readily prepared, but electronically and sterically unsymmetric DPPE (Ar12P−CH2−CH2−PAr22; Ar1≠Ar2) ligands have been less explored, mostly due to the difficulties associated with their preparation. Here we report a synthetic method for both symmetric and unsymmetric DPPEs via radical difunctionalization of ethylene, a fundamental C2 unit, with two phosphine-centered radicals, which is guided by the computational analysis with the artificial force induced reaction (AFIR) method, a quantum chemical calculation-based automated reaction path search tool. The obtained unsymmetric DPPE ligands can coordinate to several transition-metal salts to form the corresponding complexes, one of which exhibits distinctly different characteristics than the corresponding symmetric DPPE–metal complex.

Metal-Free One-Pot Multi-Functionalization of Unsaturated Compounds with Interelement Compounds by Radical Process

“…This diphosphine is composed of two types of phosphorus units, namely trivalent and pentavalent phosphorus groups. The higher reactivity of the pentavalent phosphorus radical compared to the trivalent one, and the higher carbon radical capturing ability of the trivalent phosphorus group compared to the pentavalent one, effectively caused the desired radical addition to alkenes [ 60 , 61 ]. This method could also be applied to the addition of Ph 2 P(O)–PPh 2 to alkynes, which proceeded smoothly in the presence of catalytic V-40 as the radical initiator, affording the corresponding 1-diphenylphosphinyl-2-diphenylthiophosphinyl-1-alkenes in good yields with excellent regio- and stereoselectivity ( E / Z = 95:5–99:1) ( Scheme 10 ) [ 62 ].…”

Modular and stereoselective access to cis-diphosphinoalkenes

“…9,13 Intensive screening to develop new catalytic strategies with DPPENs as optimal ligands demands more candidates with great diversity, which have not been found yet. 14 Herein, we disclose an assembly strategy for cis-diphosphinoalkenes featuring a concerted addition process, 1,4-O/S migration, and stereoselective cis-products (Fig. 1c).…”

Synthesis of Bicyclo[1.1.1]pentane (BCP)‐Based Straight‐Shaped Diphosphine Ligands**

“…To the best of our knowledge, this type of diphosphine ligand is very rare, and only a few examples of symmetric BCP-diphosphine dioxide derivatives have been reported so far. [5] Our recent radical difunctionalization of ethylene with phosphine oxide and chlorophosphine to synthesize (un)symmetric 1,2bis(diphenylphosphino)ethane derivatives [6] inspired us to synthesize BCP-diphosphine compounds from [1.1.1]propellane via this radical difunctionalization because the internal C-C bond of [1.1.1]propellane can be cleaved homolytically under radical conditions. [4] Figure 1.…”

“…Based on our previous radical difunctionalization of ethylene, [6] we first screened potential reaction conditions for the threecomponent reaction (3CR) of a phosphine oxide ((p-NMe2-C6H4)2P(=O)H (1a): 0.1 mmol), [1.1.1]propellane (1 equiv), and a chlorophosphine ((p-CF3-C6H4)2PCl ( 2a): 1 equiv) in the presence of 1 equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under irradiation with light (Table 1). We first examined various photocatalysts (1 mol%) under irradiation from blue LEDs.…”