Abstract
Quinoxaline derivatives have been synthesized by a simple, efficient, one-pot, two-component condensation of α,β-unsaturated ketones, o-phenylenediamine in the presence of a catalytic amount of 5% WO3/ZrO2 in excellent yields. The effect of electron releasing and electron with drawing substituent on the aromatic ring of phenacyl bromides on the reaction was investigated. Electron releasing groups and electron withdrawing groups did not affect significantly on the yields and the reaction times. Using 1,2-diamines possessing electron-withdrawing substituent needed longer reaction times and the yields were lower. Environmental acceptability, low cost, high yields and recyclability of the 5%WO 3 /ZrO 2 are the important features of this protocol.
Highlights
Quinoxaline derivatives are an important class of nitrogencontaining heterocycles in medicinal chemistry [1,2,3,4,5]
In order to optimize the reaction conditions, including solvents and temperature, and a suitable catalyst for the preparation of quinoxalines from o-phenylene diamine and α-halo-ketones, the condensation of o-phenylenediamine, with phenacyl bromide was chosen as a model reaction, and its behavior was studied in the presence of different catalysts and without catalyst in CH3CN at reflux temperature
For the reaction of o-phenylenediamine,with phenacyl bromide no significant loss of the product yield was observed when 5%WO3/ZrO2 was used after four times recycling (Table 2) (Scheme 2)
Summary
Quinoxaline derivatives are an important class of nitrogencontaining heterocycles in medicinal chemistry [1,2,3,4,5]. Quinoxaline derivatives have found applications in dyes, efficient electron luminescent materials, organic semiconductors, chemically controllable switches, building blocks for the synthesis of anion receptors, cavitands, and dehydoannulenes [15,16] They serve as useful rigid subunits in macrocyclic receptors in molecular recognition. Several kinds of synthetic routes toward quinoxalines have been developed, which involve condensation of 1,2-diamines with α-diketones [17], Bi-catalyzed oxidative coupling of epoxides with ene-1,2-diamines [18], cyclization-oxidation of phenacyl bromides [19,20] Many of these processes suffer from one or more limitations such as drastic reaction conditions, low product yields, the use of toxic metal salts as catalysts, and relatively expensive reagents. 2-(Biphenyl-4-yl) quinoxaline (3k): Solid; Yield 95%; mp 116118oC; IR: νmax 2924, 1722, 1677, 1533,1417, 1303, 1127, 953, 914, 844, 722 cm-1.1H NMR (300 MHz, CDCl3): δ 7.36-7.39 (d, J=7.16 Hz, 1H, Ar-H); 7.42-7.49 (t, J= 7.36 Hz, 2H, Ar-H); 7.61-7.67(d, J=7.17 Hz, 2H, Ar-H); 7.7-7.79 (m,4H, Ar-H); 8.1-8.17 (t, J=10.9 Hz, 2H, Ar-H); 8.28 -8.33 (d, J=8.30 Hz, 2H, Ar-H); 9.36 (s, 1H, =CH).13C NMR (75 MHz, CDCl3): δ 124.57, 127.77, 128.87, 129.22, 129.29, 129.69, 133.38, 134.14, 141.67, 142.37, 143
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
