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Synlett 2015; 26(01): 91-94
DOI: 10.1055/s-0034-1378923
DOI: 10.1055/s-0034-1378923
letter
Ultrasound-Mediated One-Pot Synthesis of 7-Methyl-Substituted Pyrido[4,3-d]pyrimidine Scaffolds by a Catalyst-Free Protocol
Weitere Informationen
Publikationsverlauf
Received: 18. August 2014
Accepted after revision: 12. Oktober 2014
Publikationsdatum:
11. November 2014 (online)

Abstract
A one-pot and catalyst-free protocol for the construction of 7-methyl-substituted pyrido[4,3-d]pyrimidine derivatives from ethanolic solution of 6-[2-(dimethylamino)prop-1-enyl]-1,3-dimethyluracil, aromatic aldehyde, and ammonium acetate is described under both ultrasound and thermal conditions. The ultrasound methodology is clean and the desired products are obtained with good yields in short time.
Key words
multicomponent reactions - aza-Diels–Alder - one-pot - pyrido[4,3-d]pyrimidine - ultrasound-assisted organic synthesis - green chemistrySupporting Information
- Supporting information for this article is available online at http://dx.doi.org/10.1055/s-0034-1378923.
- Supporting Information
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References and Notes
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- 6 Typical ProcedureA mixture of 6-[2-(dimethylamino)prop-1-enyl]-1,3-dimethyluracil (1b; 1 mmol), 4-fluorobenzaldehyde (2a; 1 mmol), and NH4OAc (3a; 2 mmol) in EtOH (5 mL) was ultrasonicated for 30 min in a Cole-Parmer 130 watt ultrasonic processor (Model 04714-51) at 70% amplitude. After reaction, the solvent was removed under reduced pressure, the crude product dissolved in EtOAc and directly purified by column chromatography eluting with 2:1 EtOAc–hexane to obtain pure 5-(4-fluorophenyl)-1,3,7-trimethylpyrido[4,3-d]pyrimidine-2,4-dione (4a) as an off-white solid; mp 217–219 °C. 1H NMR (300 MHz, CDCl3): δ = 7.37–7.04 (m, 4 H, Harom), 6.92 (s, 1 H, CH=CCH3), 3.57 (s, 3 H, NCH3), 3.30 (s, 3 H, NCH3), 2.66 (s, 3 H, CH3). 13C NMR (75 MHz, CDCl3): δ = 164.6, 162.2, 161.6, 160.1, 150.9, 148.0, 136.4, 130.4 (2 C), 114.9 (2 C), 106.9, 106.2, 31.1, 28.6, 25.2. MS (GC–MS): m/z = 299 [M]+. Anal. Calcd for C16H14FN3O2: C, 64.21; H, 4.71; N, 14.04; O, 10.69. Found: C, 64.20; H, 4.68; N, 14.00; O, 10.61.
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