Lanthanum-Catalyzed Regioselective Anti-Markovnikov Hydrophosphinylation of Styrenes

Abstract

A useful and convenient method for sp3 C–P­(O) bond formation via direct regioselective hydrophosphinylation of simple and readily available alkenes using a lanthanum-based N,N-dimethylbenzylamine complex (La­(DMBA)3) as a precatalyst is demonstrated. The reaction proceeds with perfect atom economy for a wide range of styrenes with secondary phosphine oxides, giving moderate to excellent yields.

Tris(benzhydryl) and Cationic Bis(benzhydryl) Ln(III) Complexes: Exceptional Thermostability and Catalytic Activity in Olefin Hydroarylation and Hydrobenzylation with Substituted Pyridines

“…However, these distances are shorter compared to the homoleptic alkyl complexes with trisubstituted methanide ligands Ln{C(SiHMe 2 ) 3 } 3 [11c] (Ln–C av La: 2.687(7) Å, Nd: 2.627(4) Å) and Ln{C(SiHMe 2 ) 2 Ph} 3 [11a] (Ln–C av La: 2.674(3) Å, Nd: 2.61(2) Å). At the same time the Ln−C benzhydryl bond lengths in 1–3 are close to the values measured in six‐coordinate benzyl (4‐Me–C 6 H 4 CH 2 ) 3 La(THF) 3 (La–CH 2 2.616(2)–2.634(2) Å), [9a] (PhCH 2 ) 3 Y(THF) 3 (2.452(3)–2.463(3) Å), [9b] (PhCHNMe 2 ) 3 Ln (Ln–CH(average) La: 2.648(3) Å, Y: 2.516(4) Å, Nd: 2.588(3) Å) [10a,b] . and aminobenzyl derivatives ( o ‐Me 2 N‐C 6 H 4 CH 2 ) 3 Ln (Ln–CH 2 (average) La: 2.645(3) Å, Y: 2.472(3) Å, Nd: 2.567(3) Å) [10c,d] …”

Hydrophosphinylation of Styrenes Catalysed by Well‐Defined s‐Block Bimetallics

“…[25][26][27][28][29] The marked alkali-metal effect (K > Na > Li) and donor influence suggests that coordination of the alkene via the π-bond to the soft potassium cation also plays a key step in the reaction mechanism. Based on these observations and literature precedent, [16,21] a proposed catalytic cycle for the hydrophosphinylation of styrenes using potassium magnesiates can be constructed (Figure 3).…”

“…[6,7] Although many transition-metal free methods for the hydrophosphination (i. e. P III -H addition) of unsaturated species have been reported, [8] the hydrophosphinylation reaction (i. e. P V -(O)À H addition) is considerably less explored. [9] Whilst catalyst-free methods have shown some success for the hydrophosphinylation of activated unsaturated substrates such as isocyanates, [10] there has been encouraging developments using s- [11][12][13][14][15][16][17] or f-block [18][19][20][21] organometallics to extend the scope of this reaction. Unlike transition-metal catalysis which relies on oxidative addition of the PÀ H bond or activation of the unsaturated substrate itself, [8,9] s-and f-block metal (pre)catalysts operate by deprotonation of HP(O)R 2 to generate a nucleophilic M-OPR 2 species which in turn can undergo insertion of the unsaturated organic substrate.…”

“…Notable examples include the use of organo-lanthanum pre-catalysts which are effective for the hydrophosphinylation of styrenes, albeit under forcing conditions and using pyridine as the reaction solvent (Scheme 1a). [21] Westerhausen and co-workers have explored the use of alkali-and alkaline-earth metal amides [M{N(SiMe 3 ) 2 } n ; M = group 1 (n = 1); M = group 2 (n = 2)] for the hydrophosphi-nylation of arylacetylenes (Scheme 1b). [16] These comprehensive studies revealed that the heavy alkali-metal amides were the most effective catalysts for this transformation, whilst the lighter congeners of both groups 1 and 2 showed poor activity.…”

Double Hydrophosphorylation of Nitriles Catalyzed by Rare-Earth-Metal Lanthanum

“…A lanthanum-based N , N -dimethylbenzylamine complex [La­(DMBA) 3 ], previously developed in our laboratory, has been shown to be an excellent precatalyst for the hydrophosphination of heterocumulenes, hydrophosphinylation of nitriles and styrenes, and the hydrophosphination and hydrophosphinylation of alkynes . Encouraged by these La­(DMBA) 3 -catalyzed organometallic transformations and in connection with our ongoing interest in producing widely applicable organophosphorus compounds catalytically, we targeted the double hydrophosphorylation (addition of H–P­(O)­(OR) 2 to unsaturated systems) of nitriles as a means to access N -(α-phosphoryl)­amidophosphates.…”