Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

• Martin Kamlar,
• Robert Reiberger,
• Martin Nigríni,
• Ivana Císařová and
• Jan Veselý

Beilstein J. Org. Chem. 2021, 17, 2433–2440, doi:10.3762/bjoc.17.160

• stereogenic carbon center with good enantioselectivity (ee up to 80%) and excellent yields (up to 97%). Keywords: aminalization; Brønsted acid; organocatalysis; PCCP; pentacarboxycyclopentadiene; Introduction Nitrogen-containing heterocyclic compounds are commonly occurring in nature and constitute the core

• employed as catalysts in asymmetric dihydroquinazolinone synthesis [18]. Regarding the above-mentioned strategies involving chiral Brønsted acids, we envisioned that chiral pentacarboxycyclopentadiene (PCCP) derivatives could be used in the enantioselective aminalization of aldehydes with anthranilamide

• of aldehydes using PCCP catalysis. Our investigation commenced with the screening of the reaction between anthranilamide (1a) and isovaleraldehyde (2a) in the presence of 10 mol % of catalyst II (Table 1). First, we turned our attention to the solvent and temperature effect concerning the yield and

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

• Gabrielle R. Hammersley,
• Meghan F. Nichol,
• Helena C. Steffens,
• Jose M. Delgado,
• Gesine K. Veits and
• Javier Read de Alaniz

Beilstein J. Org. Chem. 2019, 15, 1569–1574, doi:10.3762/bjoc.15.160

• rearrangement has been developed using a chiral Brønsted acid based on pentacarboxycyclopentadiene (PCCP). This reaction provides rapid access to valuable chiral 4-amino-2-cyclopentenone building blocks from readily available starting material and is operationally simple. Keywords: aza-Piancatelli; Brønsted

• acid; cyclopentane; furylcarbinols; PCCP; Introduction The discovery of a wide range of cyclopentane containing natural products [1][2] and biologically active molecules such as palau’amine [3][4], agelastatin A [5][6][7], pactamycin [8][9][10], and aristeromycin [11][12], has created a demand for new

• aza-Piancatelli reaction, we sought to identify other asymmetric catalytic systems capable of controlling the absolute stereochemistry. To this end, we envisioned that the chiral pentacarboxycyclopentadiene (PCCP) Brønsted acid catalyst (8) recently developed by the Lambert lab might be suitable

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• electronic spectrum of a 12 cis-to-trans isomerising toluene solution at 298 K (Δt = 120 s, [12] = 20 μM). From [59] – Reproduced by permission of the PCCP Owner Societies. Proposed isomerisation mechanisms for the thermal cis-to-trans isomerisation of the alkoxy-substituted azoderivative 4 (type-I) and the

• , for the type-II azobenzenes: azophenol 18. Transients generated by irradiation with UV-light (λ = 355 nm) for the poly-substituted azophenol 18 in ethanol (left) and toluene (right) at 298 K. ([18] = 20 μM). From [59] – Reproduced by permission of the PCCP Owner Societies. Effect of the introduction