Synlett 2012; 23(15): 2237-2240
DOI: 10.1055/s-0031-1290452
letter
© Georg Thieme Verlag Stuttgart · New York

Low-Temperature Synthesis of Pyrano- and Furo[3,2-c]quinolines via Povarov Reaction Using a Highly Ordered 3D Nanoporous Catalyst with a High Acidity

S. Chauhan
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
,
G. P. Mane
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
,
C. Anand
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
,
D. S. Dhawale
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
,
B. V. Subba Reddy
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
b   NIMS-IICT Materials Research Center, Indian Institute of Chemical Technology, Hyderabad 500 007, India
,
S. M. J. Zaidi
c   Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, Dhahran-31261, Saudi Arabia
,
Salem S. Al-Deyab
d   Department of Chemistry, Petrochemicals Research Chair, Faculty of Science, King Saud University, P.O. Box 2455 Riyadh 11451, Saudi Arabia
,
V. V. Balasubramanian
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
,
T. Mori
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
b   NIMS-IICT Materials Research Center, Indian Institute of Chemical Technology, Hyderabad 500 007, India
,
A. Vinu*
a   National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
b   NIMS-IICT Materials Research Center, Indian Institute of Chemical Technology, Hyderabad 500 007, India
e   Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane 4072, Australia, eMail: a.vinu@uq.edu.au
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Publikationsverlauf

Received: 23. Mai 2012

Accepted after revision: 25. Juni 2012

Publikationsdatum:
27. August 2012 (online)


Abstract

The imines generated in situ from aryl amines and cyclic enol ethers undergo smooth [4+2] cycloaddition with 3,4-dihydro-2H-pyran (DHP) and 2,3-dihydrofuran (DHF) using the Brønsted acid sites on the aluminosilicate wall structure of the nanoporous catalyst under mild reaction conditions to afford the corresponding pyrano- and furo[3,2-c]quinolines, respectively, in good yields with high diastereoselectivity. The high activity of the catalyst is due to its high surface area, large pore volume, and well-ordered porous structure with high acidity. In addition, the catalyst was found to be highly stable and can be reused several times without affecting the activity of the catalyst.

 
  • References and Notes

  • 9 Experimental Procedure A mixture of the aryl amine (1 mmol), dihydrofuran (2b) or dihydro-2H-pyran (2a) (2.2 mmol), and AlKIT-5 (50 mg) in MeCN (5 mL) was stirred at ambient temperature for the appropriate time (Table 1). After completion of the reaction as indicated by TLC, the mixture was filtered and washed with EtOAc (2 × 10 mL). The combined organic layers were concentrated in vacuo, and the resulting product was purified by column chromatography on silica gel (Merck, 100–200 mesh, EtOAc–hexane = 2:8) to afford pure product 3e. Analytical Data Table 1, entry 5: 1H NMR (300 MHz, CDCl3): δ = 1.43–1.54 (m, 6 H), 1.56–1.64 (m, 4 H), 2.03 (dddd, 1 H, J = 2.3, 5.6, 4.0, 12.3 Hz), 2.24 (s, 3 H), 2.56 (m, 1 H, NH), 3.27–3.34 (m, 1 H), 3.40 (m, 1 H), 3.57 (t, 1 H, J = 4.0 Hz), 3.64 (t, 2 H, J = 6.1 Hz), 5.02 (d, 1 H, J = 5.6 Hz), 6.33 (d, 1 H, J = 8.3 Hz), 6.79 (dd, 1 H, J = 2.1, 8.3 Hz), 7.21 (d, 1 H, J = 2.1 Hz). IR (KBr): ν = 3390, 2935, 1601, 2860, 1571, 1525, 1463, 1340, 1211, 1081, 805, 757 cm–1. MS (EI): m/z = 275 [M+], 202, 158, 144, 105, 91, 57. Table 1, entry 6: 1H NMR (300 MHz, CDCl3): δ = 1.60–1.73 (m, 4 H), 1.79–1.93 (m, 1 H), 1.96–2.14 (m, 1 H), 2.23 (s, 3 H), 2.53–2.67 (m, 1 H), 3.39–3.44 (m, 1 H), 3.71 (t, 2 H, J = 5.4 Hz), 3.79 (dd, 2 H, J = 3.1, 8.0 Hz), 5.06 (d, 1 H, J = 8.0 Hz), 6.42 (d, 1 H, J = 8.2 Hz), 6.80 (dd, 1 H, J = 2.1, 8.2 Hz), 7.20 (d, 1 H, J = 2.1 Hz). IR (KBr): ν = 3363, 2930, 2860, 1617, 1503, 1460, 1303, 1070, 810, 750 cm–1. MS (EI): m/z = 247 [M+], 194, 150, 136, 91.
  • 10 Synthesis of AlKIT-5 Catalyst with Different n Si/n Al Ratio The AlKIT-5 materials with different n Si/n Al ratios were synthesized using Pluronic F127 as the template in an acidic medium. In a typical synthesis, 5.0 g of F127 was dissolved in 3 g of HCl (35 wt%) and 240 g of distilled H2O. To this mixture, 24.0 g of TEOS and the required amount of the aluminium isopropoxide were added, and the resulting mixture was stirred for 24 h at 45 °C. Subsequently, the reaction mixture was heated for 24 h at 100 °C under static conditions for hydrothermal treatment. After hydro-thermal treatment, the final solid product was filtered off and then dried at 100 °C without washing and calcined at 540 °C for 10 h. The samples are denoted as AlKIT-5(x) where x denotes the n Si/n Al ratio in the final product. The molar gel composition of the reaction mixture was SiO2/Al2O3/F127/HCl/H2O = 1.0:0.041–0.071:0.0035: 0.25:116.6.