A Suzuki-Coupling-Based Generalized Route for the Synthesis of 2-(2/3-Thienyl)cycloalk-1-ene-1-carbaldehydes as Precursors for Condensed Thienophenanthraquinones

Abstract

Experimental:2-Thienylboronic acid, 3-thienylboronic acid, 2-fomyl-3-thienylboronic acid and 2-acetyl-3thienylboronic acid, tetrakis(triphenylphosphine)palladium(0), were purchased from Sigma Aldrich Chemicals Pvt. Ltd.. Other chemicals were purchased from E. Merck, India, SRL, or Ranbaxy Pvt. Ltd. The bromoaldehydes were synthesized from respective ketones by Vilsmeier-Haack reaction following the standard procedure. Solvents were dried following standard literature procedure. 1 H NMR spectra were recorded on Bruker 500 MHz (at I.A.C.S, Kolkata), Bruker 400 MHz (at I.A.C.S, Kolkata and Kalyani University, Nadia) and Bruker 300 MHz (Calcutta University, Kolkata). 13 C-NMR (125 MHz / 100 MHz / 75 MHz) spectral data were obtained from IACS Kolkata, Kalyani University, Nadia and Calcutta University, Kolkata respectively. ESI mass spectra (HRMS) were recorded on a micro mass Q-TOF mass spectrometer (serial no. YA 263) at I.A.C.S, Kolkata. IR spectra were recorded on JASCO FT/IR 680 PLUS spectrometer. 2-(2-thienyl)cyclooct-1-ene-1-carbalaldehyde (2c): Faint yellow viscous oil; yield: 176 mg (80 %, 0.8 mmol). IR (KBr) ν max : 1660.41 cm -1 ; 1 H NMR (300 MHz, CDCl 3 ): δ 1.40-1.41 (m, 4H), 1.53 (m, ill split, 2H), 1.63 (m, ill split, 2H), 2.48 (t, J = 6.0 Hz, 2H), 2.68 (t, J = 6.3 Hz, 2H), 6.88-6.95 (m, 2H), 7.33 (dd, J = 1.2 Hz & 5.1 Hz, 1H), 9.58 (s, 1H) ppm; 13 C NMR (75 MHz, CDCl 3 ): δ 24.94, 26.09, 26.69, 29.13, 30.02, 36.21, 126.98, 127.81, 130.47, 140.67, 140.76, 153.68, 192.65 ppm; HRMS (ESI, 70 ev): m/z [M+H] + calcd for C 13 H 17 SO: 221.0922; found: 221.0997. 1-(2-thienyl)-3,4-dihydronaphthalene-2-carbaldehyde (2d): Colourless solid; yield: 173 mg (72 %, 0.72 mmol); m.p. 84-86 °C. IR (KBr) ν max : 1654.62 cm -1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 2.60 (dd, J = 7.2 Hz & 9.2 Hz, 2H), 2.79 (dd, J = 7.2 Hz & 14.4 Hz, 2H ), 7.01-7.04 (m, 2 H ), 7.06 ( dd, J = 3.6

Application of the intramolecular Diels–Alder vinylarene (IMDAV) reaction for the synthesis of benzo-, carbocyclo-, thienothiopheneisoindolecarboxylic acids and its limitations

“…Bromoaldehydes 21a–e were introduced into the Suzuki–Miyaura cross-coupling reaction with various thiopheneboronic acids. 15 It should be noted that during the initial attempts to carry out the cross-coupling reaction according to the procedure described in the literature, 15 rather low yields were obtained which brought the urge to optimize the reaction conditions. Initially, the reaction was performed in DMF in the presence of triethylamine.…”