Iron‐Salt‐Promoted Highly Regioselective α and β Hydrophosphination of Alkenyl Arenes

Abstract

Dedicated to Professor Irina Petrovna BeletskayaThe catalytic addition of phosphines to alkenes (hydrophosphination) is an attractive process (Scheme 1). [1] It is a 100 % atom-economical reaction that uses widely available and inexpensive starting materials. It offers an access to alkylphosphines, which are useful ligands, [2] organocatalysts, [3] and reagents in organic synthesis. [4] However, due to the high energy of the P À H bond (E = 77 kcal mol À1 ), [5] the reaction usually requires activation by radical initiators. [1c, 6] Thermal-, [7] acid-, [8] and base-promoted [9] reactions have also been applied, although less frequently. Metal-and lanthanide-catalyzed processes were also reported recently. [1c, 10] Whatever the method, the addition usually proceeds in an anti-Markovnikov way leading to the b adduct B (addition of the phosphorus atom to the terminal carbon atom of a terminal alkene). In contrast, the selective formation of the [a] Dr.

Markovnikov versus anti‐Markovnikov Hydrophosphination: Divergent Reactivity Using an Iron(II) β‐Diketiminate Pre‐Catalyst

“…To the best of our knowledge, only two such examples have been reported using iron, both by Nakazawa and co‐workers and both involving heating to 110 °C for several days (Scheme a) . However, a challenge that remains in the HP of alkynes is being able to selectively mono‐hydrophosphinate in a Markovnikov fashion . Only one such example of the HP of alkynes exists, which uses nickel catalysis, but with no analytical data, harsh reaction conditions, and moderate selectivity .…”

Preparation of phosphines through C–P bond formation

“…Most research has focused on the use of platinum [92–96], palladium [97–99] or nickel [100–104] complexes. Other catalysts that have been less investigated are iron [105–107], rhodium [108–110], lanthanides [111–114], copper [115] and alkaline-earth metals [114,116]. The catalyst activates either the P - nucleophile or the C-electrophile.…”

Aerobic addition of secondary phosphine oxides to vinyl sulfides: a shortcut to 1-hydroxy-2-(organosulfanyl)ethyl(diorganyl)phosphine oxides

“…Among them, the addition of P(X)–H (X = none, O, S or Se) to diverse alkenes is one of the most powerful and 100% atom-economic approaches to construct new C–P bonds, that provide straightforward access to tertiary phosphines and their chalcogenides [8–12]. Conventionally, the activation of the P–H bonds in this reaction is achieved by using radical initiators [13–15], Brønsted/Lewis acids [16–17] and bases [18–20] as well as transition metal catalysts [21–23]. Also, examples of the microwave-assisted [24–25] and photoinduced [26] addition are described.…”