Gas-Phase Pyrolysis in Organic Synthesis: Rapid Green Synthesis of 4-Quinolinones

Abstract

Gas-phase pyrolysis of aminomethylene Meldrum’s acid derivatives gave quinolinones and/or amines depending on the ­nature of arylamino moiety. Effect of substituent on reaction rate and nature of pyrolysis products supports the suggested intramolecular nucleophilic substitution reaction via initially formed keteneamine intermediate.

Meldrum’s acid - pyrolysis - 4-quinolinones

References and Notes

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12

Static Pyrolysis of 8-j
The substrate (0.2 g) was introduced in the Pyrex reaction tube (12 cm length and 1.5 cm internal diameter). The tube was sealed under vacuum (0.02 m bar) and placed in the pyrolyzer for 900 s at 300 °C. The content of the tube was then separated by preparative high-performance liquid chromatography (HPLC) and was analyzed by ¹H NMR, ¹³C NMR, IR and GC-MS. Relative and percent yields were determined from NMR.

13

Flash Vacuum Pyrolysis of 8a-j The sample was volatilized from a tube in a Buchi Kugelrohr oven through a 30 × 2.5 cm horizontal-fused quartz tube and was heated externally by a cabolite Eurotherm tube furnace MTF-12/38A to 600 °C. The products were collected in a U-shaped trap cooled in liquid nitrogen. The whole system was maintained at a pressure of 10^-2 Torr by an Edwards Model E2M5 high-capacity rotary oil pump, the pressure being measured by a Pirani gauge situated between the cold trap and pump. Under these condition the contact time in the hot zone was estimated to be 10 ms. Products collected in the U-shaped trap were analyzed by ¹H NMR, ¹³C NMR, IR and GC-MS. Relative and percent yields were determined from NMR.
Compounds 11a,c,d,f-h,j-n, 16, and 17 has been reported earlier and proved to be identical with products obtained here. [19-27]

14

6-Methyl-1 H -quinolin-4-one ( 11b)
Mp 240-242 °C. IR (KBr): 3050 (NH), 1625 (CO) cm^-1. LC-MS: m/z (%) = 159 (100) [M⁺]. ¹H NMR (400 MHz, DMSO): δ = 2.39 (s, 3 H, CH₃), 6.0 (d, 1 H, J = 7.2 Hz, quinoline-H3), 7.45 (d, 1 H, quinoline-H8), 7.48 (d, 1 H, quinoline-H7), 7.86 (d, 1 H, J = 7.2 Hz, quinoline-H2), 8.31 (s, 1 H, quinoline-H5), 11.72 (br s, 1 H, D₂O exchangeable, NH). ¹³C NMR (DMSO, 100 MHz): δ = 21.55, 109.09, 119.18, 124.70, 125.96, 134.31, 134.57, 138.67, 140.50, 178.48. DEPT 135: δ = 21.55, 109.09, 119.18, 124.70, 125.96, 134.57, 140.50.

15

7-Bromo-1 H -quinolin-4-one ( 11e)
Mp 242-244 °C. LC-MS: m/z = 225 [M + 1]. ¹H NMR (400 MHz, DMSO): δ = 6.04 (d, 1 H, H3, J = 7.37 Hz), 7.52 (d, 1 H, J = 8.56 Hz), 7.74 (s, 1 H, H-5), 7.82 (d, 1 H, J = 7.37 Hz, H2), 8 (d, 1 H, J = 8.56 Hz, H6), 11.22 (br, 1 H, NH). ¹³C NMR (100 MHz, DMSO): δ = 111.5, 120.4, 123.2, 126, 128.4, 132.7, 141, 143.4, 177.4.

16

5-Bromo-1 H -quinolin-4-one ( 11i)
Mp 234-236 °C. IR (KBr): 1645 (CO) cm^-1. LC-MS: m/z = 225 [M + 1]. ¹H NMR (400 MHz, DMSO): δ = 6.06 (d, 1 H, H3, J = 7.24 Hz), 7.41-7.47 (m, 3 H, ArH), 7.93 (d, 1 H, J = 7.24 Hz, H-2), 11.18 (br, 1 H, NH). ¹³C NMR (75 MHz, DMSO): δ = 110.3, 119.5, 121.5, 125.6, 127.2, 130.6, 139.3, 142, 177.

17 Smith MB. March J. March’s Advanced Organic Chemistry: Reaction Mechanisms and Structure   5th ed.:  J. Wiley and Sons, Inc.; New York: 2001.  p.68 

18

Pyrazino[1,2- a ]pyrimidin-4-one ( 19) Mp 178-180 °C. IR (KBr): 1692 (CO) cm^-1. LC-MS: m/z = 148 [M + 1]. ¹H NMR (400 MHz, DMSO): δ = 6.67 (d, 1 H, J = 6.44 Hz, pyrimidine-H), 8.19 (d, 1 H, J = 4.64 Hz, pyrazine-H), 8.41 (d, 1 H, J = 6.44 Hz, pyrimidine-H), 8.73 (d, 1 H, J = 4.64 Hz, pyrazine-H), 9.13 (s, 1 H, pyrazine-H). ¹³C NMR (75 MHz, DMSO): δ = 109.6, 118.2, 133.0, 145.8, 154.2, 155.9, 156.8. DEPT 135: δ = 109.6, 118.2, 133.0, 154.2, 155.9. Anal. Calcd for C₇H₅N₃O (147.14): C, 57.14; H, 3.43; N, 28.56. Found: C, 57.53; H, 3.62; N, 28.83.

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