ChemInform Abstract: Enantioselective Rhodium‐Catalyzed [4 + 2 + 2] Cycloaddition of Dienyl Isocyanates for the Synthesis of Bicyclic Azocine Rings.

Yu, Robert T.; Friedman, Rebecca Keller; Rovis, Tomislav

doi:10.1002/chin.201006177

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“…Similarly, 2-Ru Cy and 2-Mn Cy showed no conversion under analogous conditions, as determined by 31 P NMR spectroscopy (Scheme 4a). 37 In contrast, the treatment of 3-Mn Cy with 2 equiv of CyOH for 1 h at 100 °C resulted in complete conversion of 3-Mn Cy to 1-Mn and the free carbamate CyNHC(O)OCy, as indicated by 1 H NMR spectroscopy (Scheme 4b). 38 We next compared 1-Ru, 1-Fe, and 1-Mn as catalysts for the dehydrogenative reaction of N-cyclohexylformamide with cyclohexanol to form CyNHC(O)OCy (Table 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Metal Identity Effects in the Pincer Complex-Catalyzed Dehydrogenative Coupling of Formamides with Alcohols to Form Carbamates

Kassie,

Castro De la Torre,

Remy

et al. 2023

Organometallics

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This manuscript describes the impact of metal (ruthenium versus iron versus manganese) on the PNP pincer complex-catalyzed dehydrogenative coupling of formamides with alcohols to yield carbamates. Studies are conducted to compare the structure and reactivity of key organometallic intermediates as a function of metal. These reveal that all three pincer catalysts undergo fast reaction with isocyanates (the initial organic products of formamide dehydrogenation) to form off-cycle metallacyclic species. However, the structures and reactivities of these intermediates vary as a function of metal. The N-bound isomer of the metallacycle is formed with Fe (literature) and Ru (this work), while both O-bound (kinetic) and N-bound (thermodynamic) metallacycles are observed with Mn (this work). At 100 °C, the O-bound Mn cycloadduct reacts rapidly with cyclohexanol to release the pincer catalyst along with the corresponding carbamate. In contrast, all three of the N-bound metallacycles show dramatically lower reactivity toward catalyst regeneration under analogous conditions. The reactivity of the pincer complexes toward formamide dehydrogenation also varies as a function of metal, with Ru and Fe ≫ Mn at 100 °C. Overall, the Mn pincer complex is an effective catalyst for the conversion of a variety of formamides and alcohols to carbamates at 150 °C with catalyst loadings as low as 1 mol %. The catalyst performance and substrate scope are comparable to those of the Fe analogue.

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Section: ■ Results and Discussionmentioning

confidence: 99%

“…Substrate Scope of 1-Mn-Catalyzed Dehydrogenative Coupling of Formamides with Alcohols at 150 °Ca Conditions: 1 mol % of 1-Mn, 0.5 mmol of formamide, 0.6 mmol of alcohol, 0.5 mL of toluene, 150 °C, 24 h. Yields determined by1 H NMR spectroscopy and GCMS. b 2 mol % of 1-Mn and 2.5 mmol of MeOH.…”

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confidence: 99%