Iron-Catalyzed Reductive Coupling of Nitroarenes with Olefins: Intermediate of Iron–Nitroso Complex

Abstract

Using a single half-sandwich iron(II) compound, Cp*Fe(1,2-Ph 2 PC 6 H 4 S)(NCMe) (Cp* − = C 5 Me 5 − , 1) as a catalyst, reductive coupling of nitroarenes with olefins has been achieved by a well-defined iron(II)/(EtO) 3 SiH system. Through either inter-or intramolecular reductive coupling, various branched amines and indole derivatives have been directly synthesized in one-pot. Mechanistic studies showed that the catalysis is initiated by activation of nitroarenes by the iron(II) catalyst with silane, generating iron−nitrosoarene intermediate for the C−N bond coupling.

Hydrogen Atom Transfer‐Mediated Domino Cyclisation Reaction to Access (Spiro)Quinazolinones

“…Subsequently, N ‐cyanamide alkenes have been developed as radicophiles for 1,3‐dicarbonyl, trifluoromethyl, phosphoryl, and sulfonyl radicals . Since its discovery in the early 1960s, metal‐hydride hydrogen atom transfer (HAT) has become a widely established method for the generation of carbon‐centred radicals from alkenes and a variety of radicophiles have proven compatible . As an extension of our previous methodology, which utilised HAT to mediate cyclisation between alkenes and nitriles, we looked to develop this further by utilising N ‐cyanamide alkenes to access complex (spiro)quinazolinone scaffolds (Scheme b).…”

“…[10] Since its discovery in the early 1960s, [11] metal-hydride hydrogen atom transfer (HAT) has become aw idely established methodf or the generation of carbon-centred radicals from alkenes [12] and av ariety of radicophiles have provenc ompatible. [13][14][15][16][17][18][19][20][21][22] As an extension of our previousm ethodology,w hich utilised HATt om ediate cyclisation between alkenes and nitriles, [17] we looked to developt his furtherb yu tilising N-cyanamide alkenest oa ccess complex (spiro)quinazolinone scaffolds (Scheme 2b). It has been shown that the introduction of sp 3 centres, such as the spirocentre of spirocycles, can greatlye nhance am olecule's potential to be a drug candidate.…”

Site-specific Umpolung amidation of carboxylic acids via triplet synergistic catalysis

“…Replacement of FeI 2 with other iron-based catalysts also led to sharply decreased yields (entries 7 and 8). It was speculated that iron-based catalysts would not only accelerate the reduction of R 3 P = O to R 3 P but would also favor the reduction of nitrobenzene to nitrosobenzene under mild conditions 26 , 50 – 52 . Notably, the use of other silanes in place of PhSiH 3 did not improve the reaction yields (entries 9 and 10, and also see Supplementary Table 3 for details).…”

Recent Progress on Reductive Coupling of Nitroarenes by Using Organosilanes as Convenient Reductants

“…II) as a robust catalyst for the reductive coupling of nitroarenes and styrenes under a similar iron(II)/(EtO) 3 SiH system (Scheme 8). [23] Notably, the reductive workup with Zn/HCl (aq.) is not necessary in this case.…”