Nickel(II)‐Magnesium‐Catalyzed Cross‐Coupling of 1,1‐Dibromo‐1‐alkenes with Diphenylphosphine Oxide: One‐Pot Synthesis of (E)‐1‐Alkenylphosphine Oxides or Bisphosphine Oxides

Abstract

A novel nickel(II)-magnesium-mediated cross-coupling of diphenylphosphine oxide with a variety of 1,1-dibromo-1-alkenes has been developed, which provides a powerful and general methodology for the stereoselective synthesis of various (E)-1-alkenylphosphine oxides or bisphosphine oxides, with operational simplicity of the procedure, good to high yields and broad substrate applicability. Mechanistic studies reveal that the reaction might involve a Hirao reduction, cross-coupling and Michael addition.Transition metal-catalyzed carbon-phosphorus bond formation by cross-coupling reactions has attracted increasing attention in the last two decades due to its wide applicability in biological, pharmaceutical, material and catalytic sciences. [1] Alkenylphosphine oxides and bisphosphine oxides are important classes of phosphorus-containing, extremely valuable compounds in organic chemistry. For example, alkenylphosphine oxides are endowed with a wide-range of biological activities, [2] outstanding flame-retardant properties [3] and eminent metal-complexing abilities as ligands. [4] Furthermore, they can serve as useful precursors in the synthesis of a variety of synthetically elaborated bifunctional adducts by the ready addtion of several nucleophiles to the double bond. [5] Bisphos-phine oxides are used as organoextractions in hydrometallurgy, [6] and are key intermediates for the preparation of various valuable phosphine ligands [7] in homogeneous catalysis, organocatalysts for the allylation of N-acylhydrazones [8] and stereoselective direct aldol reactions of trifluoroethyl thioestesters. [9] Recently, a few transition metal-catalyzed methods for the preparation of alkenylphosphine oxides have continuously emerged including the Pd-catalyzed cross-coupling of alkenyl halides with phosphine oxides, [10] olefin cross-metathesis, [11] Cu-catalyzed decarboxylative coupling, [12] cleavage of silylepoxides [13] or stannyloxiranes [14] with lithium diphenylphosphide, hydrophosphination of terminal alkynes with diphosphines and hydrosilanes in the presence of oxygen, [15] Rh-catalyzed reaction of 1-alkynylphosphines with water, [16] in situ reactions of functionalized mono-A C H T U N G T R E N N U N G ylides with carbonyl compounds [17] and transition metal-catalyzed addition of P(O)H compounds to alk-A C H T U N G T R E N N U N G ynes. [18,20] Bisphosphine oxides can be prepared by several methods such as the Pd- [18f,19] or Rh-catalyzed [20] double hydrophosphinylation of alkynes, substitution reactions of 1,2-dichloride complex, [21] double nucleophilic addition of secondary phosphine oxides to methylacetylene, [22] Kolbe electrolytic coupling reactions of phosphinoyl-acetic or propanoic acids [23] and catalytic olefin cross-or homo-metathesis. [11,24] However, these traditional procedures suffer from relatively strict reaction conditions, low selectivity, poor substrate scope or unsatisfactory yield, and there is still a strong need for developing more convenient and efficient approaches to alkenylphosphine oxides and b...

A surprising mechanism lacking the Ni(0) state during the Ni(II)-catalyzed P–C cross-coupling reaction performed in the absence of a reducing agent – An experimental and a theoretical study

“…A part of the P-C couplings were performed using Ni(II) salts together with Zn or Mg as the reducing agent to form Ni(0) [12][13][14][15][16][17][18][19]. In a part of the cases P-ligands [12,19], in other instances N-ligands [13][14][15][16][17][18][19] were used to form the Ni complexes. The theoretical calculations [18] of Zhao and co-workers justified the involvement of Ni(0) in the usual catalytic cycle starting with oxidative addition of the, in this case, vinyl bromide reactant.…”

Scope and Limitations of the s‐Block Metal‐Mediated Pudovik Reaction

“…Depending on the precatalyst, radical and polar reaction different mechanisms have been discussed. Thus, diverse catalyst systems have been investigated such as for example, Al 2 O 3 /KOH, palladium(0), ytterbium(II), rhodium(I), nickel, potassium, and bases in general . In the presence of air the product range deviates and radical mechanisms account for the observed products and by‐products …”

Mono and double Mizoroki–Heck reaction of aryl halides with dialkyl vinylphosphonates using a reusable palladium catalyst under aqueous medium

“…Alkenylphosphonates are important molecules that have been widely applied in organic synthesis, 1-14 materials science, [15][16][17] medical chemistry, [18][19][20][21] and as polymer additives 22 and ame retardants. 23,24 Transition-metal-catalyzed reactions for the formation of alkenylphosphonates mainly include crosscoupling of P(O)H with vinyl halides or pseudo halides, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] olen cross-metathesis, 41 reaction of HP(O) compounds with alkynes [42][43][44][45][46][47][48][49][50] or alkenes, 51,52 Suzuki-Miyaura coupling of boronic acids with vinylphosphonates, [53][54][55][56][57][58][59] and Mizoroki-Heck reaction of vinylphosphonates with various aryl partners. [60]…”