2026-27-9Relevant articles and documents
Sequential Formal [4+1]-Cycloaddition, C?H Functionalization and Suzuki–Miyaura Cross-Coupling for the Synthesis of Trisubstituted Isoxazolines
Ioffe, Sema L.,Sukhorukov, Alexey Yu.,Tabolin, Andrey A.,Ushakov, Pavel Yu.
, p. 2680 - 2693 (2021/06/25)
Suzuki–Miyaura cross-coupling reaction of 3-bromomethyl isoxazolines with arylboronic acids was suggested as final C?C bond forming step in convenient diastereoselective route to trisubstituted isoxazolines. The required bromides were readily available fr
Pd-catalyzed chemo-selective mono-arylations and bis-arylations of functionalized 4-chlorocoumarins with triarylbismuths as threefold arylating reagents
Rao, Maddali L.N.,Kumar, Abhijeet
, p. 6995 - 7005 (2015/03/14)
Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2-4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones (3.27-3.30). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of (R)-tolterodine.
Preparation, structure, and reactivity of nonstabilized organoiron compounds. Implications for iron-catalyzed cross coupling reactions
Fuerstner, Alois,Martin, Ruben,Krause, Helga,Seidel, Guenter,Goddard, Richard,Lehmann, Christian W.
, p. 8773 - 8787 (2008/12/23)
A series of unprecedented organoiron complexes of the formal oxidation states -2, 0, +1, +2, and +3 is presented, which are largely devoid of stabilizing ligands and, in part, also electronically unsaturated (14-, 16-, 17- and 18-electron counts). Specifically, it is shown that nucleophiles unable to undergo β-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) to Fe(2+) and then exhaustively alkylate the metal center. The resulting homoleptic organoferrate complexes [(Me4Fe)(MeLi)] [Li(OEt2)]2 (3) and [Ph4Fe][Li(Et 2O)2][Li(1,4-dioxane)] (5) could be characterized by X-ray crystal structure analysis. However, these exceptionally sensitive compounds turned out to be only moderately nucleophilic, transferring their organic ligands to activated electrophiles only, while being unable to alkylate (hetero)aryl halides unless they are very electron deficient. In striking contrast, Grignard reagents bearing alkyl residues amenable to β-hydride elimination reduce FeXn (n = 2, 3) to clusters of the formal composition [Fe(MgX)2]n. The behavior of these intermetallic species can be emulated by structurally well-defined lithium ferrate complexes of the type [Fe(C2H4) 4][Li(tmeda)]2 (8), [Fe(cod)2][Li(dme)] 2 (9), [CpFe(C2H4)2][Li(tmeda)] (7), [CpFe(cod)][Li(dme)] (11), or [Cp*Fe(C2H4) 2][Li(tmeda)] (14). Such electron-rich complexes, which are distinguished by short intermetallic Fe-Li bonds, were shown to react with aryl chlorides and allyl halides; the structures and reactivity patterns of the resulting organoiron compounds provide first insights into the elementary steps of low valent iron-catalyzed cross coupling reactions of aryl, alkyl, allyl, benzyl, and propargyl halides with organomagnesium reagents. However, the acquired data suggest that such C-C bond formations can occur, a priori, along different catalytic cycles shuttling between metal centers of the formal oxidation states Fe(+1)/Fe(+3), Fe(0)/Fe(+2), and Fe(-2)/Fe(0). Since these different manifolds are likely interconnected, an unambiguous decision as to which redox cycle dominates in solution remains difficult, even though iron complexes of the lowest accessible formal oxidation states promote the reactions most effectively.
