Synthesis and biological activity of some pyrrolyl derivatives of pyrazoloner-5

Synthesis of the Ring C Pyrrole of Native Chlorophylls and Bacteriochlorophylls

“…General Methods. 1 H NMR and 13 C NMR spectra were collected at room temperature in CDCl 3 unless noted otherwise. Electrospray ionization mass spectrometry data are reported for the molecular ion or protonated molecular ion.…”

“…1 H NMR (300 MHz): δ 1.09 (d, J = 7.5 Hz, 18H), 1.41 (q, J = 7.4 Hz, 3H), 6.29 (dd, J 1 = 2.9 Hz, J 2 = 1.4 Hz, 1H), 6.68 (d, J = 2.6 Hz, 1H), 6.71−6.75 (m, 1H). 13 C NMR (75 MHz): δ 11.5, 17.7, 97.9, 113.0, 123.3, 124.7. HRMS (ESI-TOF) m/z: [M + H] + calcd for C 13 H 25 BrNSi, 302.0934; found, 302.0932.…”

“…1 H NMR (300 MHz): δ 1.13 (d, J = 7.4 Hz, 18H), 1.38−1.50 (m, 3H), 2.16 (s, 3H), 6.17 (d, J = 1.7 Hz, 1H), 6.56 (d, J = 1.1 Hz, 1H), 6.72 (t, J = 2.4 Hz, 1H). 13 3,4-Dibromo-1-(triisopropylsilyl)pyrrole (TIPS-pyrrole-Br 2 ). Following a reported procedure 18 with modifications for 4-fold larger scale, a solution of TIPS-pyrrole (10.0 g, 45.0 mmol) in anhydrous THF (140 mL) was treated slowly with NBS (16.0 g, 90.0 mmol) at −78 °C under argon.…”

“…Results illustrating this methodological lacuna are as follows: Claisen condensation of β-acetylpyrroles with dialkyl carbonates or methyl cyanoformate was successful with N -substituted substrates ( Me-I → Me-II , Scheme ), but N -unsubstituted pyrroles ( I ) yielded unwanted products due to N -alkylation ( Me-I , Me-II ) and further reaction of the pyrrole-attached 3-methoxy-1,3-dioxopropyl moiety ( III ) Pd-mediated carbonylation or alkoxycarbonylation enabled formation of the 3-methoxy-1,3-dioxopropyl unit in fair to good yields ( Ts-IV → Ts-V ) but has been demonstrated only for N -substituted pyrroles. Acylation of a malonate with a pyrrole acid chloride, or of a pyrrole with a malonyl chloride, is restricted to deactivated pyrroles with a full complement of substituents (affording, e.g., VI ). ,− Pyrrole VII was used in pioneering studies of Nazarov cyclization, − but procedure, scale, and characterization data were not provided for the stated synthesis from 3-carboxypyrrole , or 3-acetylpyrrole …”

“…Acylation of a malonate with a pyrrole acid chloride, or of a pyrrole with a malonyl chloride, is restricted to deactivated pyrroles with a full complement of substituents (affording, e.g., VI ). ,− …”