Rh^III‐katalysierte C‐H‐Aktivierung mit Pyridotriazolen: direkter Zugang zu Fluorophoren zur Metallerkennung

Abstract

Die erste C-H-Aktivierung mit Pyridotriazolen als Kupplungspartner wurde mit einem Rh III -Katalysator verwirklicht. Die Pyridotriazole kçnnen dabei als neue Carbenvorstufen in der C-H-Aktivierung genutzt werden, um gezielt neue fluoreszierende Strukturen zu synthetisieren. Diese Fluorophore mit wählbaren Eigenschaften kçnnen zur Detektion von Metallionen genutzt werden.

Cross‐Coupling of α‐Carbonyl Sulfoxonium Ylides with C−H Bonds

“…We hypothesized that after group-directed cyclometallation involving metal-catalyzed CÀHb ond cleavage, B,t hus formed, would undergo migratory insertion of a-carbonyl sulfoxonium ylides via intermediates C and/or D to give E. This intermediate would then liberate the cross-coupling products upon protodemetallation ( Figure 1c). Significantly, the realization of this design would address the potential safety issues of the recently reported group-directed C À H functionalization reactions with diazo compounds [4] and their in situ precursors such as triazoles [5] or hydrazones. [6] Moreover, it would complement the scope of recently reported rhodium-catalyzed annulation reactions with cyclopropenes [7] and enynes, [8] reactions which also likely proceed by migratory insertion similar to the postulated evolution of D into E. Finally,itwould also expand the scope of the well-established CÀHinsertion chemistry of metal carbenoids generated from diazo compounds.…”

“…[14] Alternatively,t he pyrimidine directing group,which enabled the formation of 6u,can be cleaved to give 21 [Eq. (5)]. M oreover,t he quinoline 23 a was obtained in 77 %y ield by cross-coupling of 22 and 2b and was then converted into the benz[c]acridine 24 a in one step and 60 % yield, after treatment with acatalytic amount of [{Cp*IrCl 2 } 2 ] in am ixture of isopropanol and water (Scheme 1).…”

Cross‐Coupling of α‐Carbonyl Sulfoxonium Ylides with C−H Bonds

“…This intermediate would then liberate the cross‐coupling products upon protodemetallation (Figure c). Significantly, the realization of this design would address the potential safety issues of the recently reported group‐directed C−H functionalization reactions with diazo compounds and their in situ precursors such as triazoles or hydrazones . Moreover, it would complement the scope of recently reported rhodium‐catalyzed annulation reactions with cyclopropenes and enynes, reactions which also likely proceed by migratory insertion similar to the postulated evolution of D into E .…”

Rhodium(II)‐Catalyzed Formal [4+1]‐Cycloaddition of Pyridotriazoles and Propargyl Alcohols: Synthesis of 2,5‐Dihydrofurans

“…[15] In the last decade, Gevorgyan and others have reported a variety of cycloaddition reactions with pyridotriazole as a-pyridyl carbene precursor. [21] Inspired by these advances, and in continuation of our interest in catalytic metal carbene transformations, [9,14] we envisioned that a formal [4 + 1]-cycloaddition of pyridotriazoles and aryl propargyl alcohols in the presence of a compatible dirhodium catalyst could be realized for the synthesis of 2-pyridyl 2,5-dihydrofuran. [20] However, no cyclization reaction with this species as a "one-C" building block has been disclosed.…”

“…[20] However, no cyclization reaction with this species as a "one-C" building block has been disclosed. [21] Inspired by these advances, and in continuation of our interest in catalytic metal carbene transformations, [9,14] we envisioned that a formal [4 + 1]-cycloaddition of pyridotriazoles and aryl propargyl alcohols in the presence of a compatible dirhodium catalyst could be realized for the synthesis of 2-pyridyl To probe the feasibility of our assumption, we initially chose 7-chloro-pyridotriazole (1 a) and 3phenylpropargyl alcohol (2 a) as the standard substrates, and dirhodium catalysts were examined in 1,2dichloroethane (DCE) at 25 8C. Although high reactivity was observed for these tested rhodium catalysts, low selectivity was obtained in the cases with Rh 2 (OAc) 4 or Rh 2 (Oct) 4 catalyst ( Table 1, entries 1&2).…”