Sulfuric Acid → 8-Bromo-4-methyl-3,4-dihydropyrimido[1,2-a]indol-10(2H)-one
Reaction equation
OS(O)(=O)=O.[Br:6][C:7]1[CH:15]=[CH:14][C:13]2[N:12]3[CH:16]([CH3:20])[CH2:17][CH2:18][N:19]=[C:11]3[C:10]3(OCCC[O:21]3)[C:9]=2[CH:8]=1.[NH4+].[OH-]>>[Br:6][C:7]1[CH:15]=[CH:14][C:13]2[N:12]3[CH:16]([CH3:20])[CH2:17][CH2:18][N:19]=[C:11]3[C:10](=[O:21])[C:9]=2[CH:8]=1Participants
Procedure
To cold concentrated H2SO4 (3 mL) was added 8′-bromo-4′-methyl-3′,4′-dihydro-2′H-spiro[1,3-dioxane-2,10′-pyrimido[1,2-a]indole] (0.252 g, 0.747 mmol) in four portions with cooling in an ice bath. The reaction was then allowed to stir at room temperature for 1 hr. The mixture was poured onto ice and basified with NH4OH to pH 11 with cooling in an external ice bath. The reaction mixture was extracted with Et2O (2×). The combined organic extracts were dried over Na2SO4, filtered, and concentrated. The crude product was purified on Biotage KP silica gel eluting with CH2Cl2/CH3OH/NH4OH (96/2/1) to give the title compound as a red solid (0.138 g, 66% ). Anal. Calc'd for C12H11BrN2O: C, 51.64; H, 3.97; N, 10.04; Found: C, 51.23; H, 3.89; N, 9.88. NMR (300 Mz, DMSO-d6): consistent. MS: (ES+) m/z 278/280 [M+H]; 1 Br pattern observed. m.p.: 127-129° C.
Workup
- temperaturewith cooling in an ice bath
- additionThe mixture was poured onto ice
- temperaturewith cooling in an external ice bath
- extractionThe reaction mixture was extracted with Et2O (2×)
- dry with materialThe combined organic extracts were dried over Na2SO4
- filtrationfiltered
- concentrationconcentrated
- customThe crude product was purified on Biotage KP silica gel eluting with CH2Cl2/CH3OH/NH4OH (96/2/1)
Sources & evidence
- ORD record
- ord-072113834f414f289f3b7b6b94bdcdfe
- Source dataset
- uspto-grants-2007_08
- Patent number
- US07256198B2
Reaction notes
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