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A solution of 2,4,6-trimethylaniline (6.86 g, 5 mmol) in dry THF (100 mL) under an atmosphere of N2 was cooled to -78° C. and n-butyllithium (21 mL, 2.5M solution in hexanes) was added dropwise. The mixture was allowed to warm to 0° C., and dry CO2 gas was bubbled in for 2-3 minutes. The excess CO2 was removed under vacuum, and after the addition of further THF to replace that lost by evaporation, the solution was recooled to -78° C. n-Butyllithium (22 mL, 2.5M solution in hexanes) was again added dropwise, and the temperature was then allowed to rise slowly to -10° C. where a deep red colored solution was obtained. After a further 30 minutes at that temperature, the mixture was again recooled to -78° C. and CO2 gas was bubbled in until the red color disappeared. The reaction mixture was allowed to warm to 20° C., and after removal of the solvent, 0.1M HCL (50 mL) was added to initiate both deprotection of the nitrogen and ring-closure. The resulting mixture was extracted with EtOAc, and this was then washed successively with 0.1M HCl, water, and dilute aqueous Na2CO3. After drying (Na2SO4), the solvent was removed under vacuum, to leave an oil which was purified by chromatography on Al2O3 to give 1,6-dimethyl-2-indolinone (3.37 g, 42% yield) [VII: R1 =6-Me; R3 =Me]; mp (hexane) 94.5°-96° C.

1. customdry CO2 gas was bubbled in for 2-3 minutes
2. customThe excess CO2 was removed under vacuum
3. additionafter the addition of further THF
4. customthat lost by evaporation
5. customwas recooled to -78° C.
6. additionwas again added dropwise
7. customto rise slowly to -10° C.
8. customwas obtained
9. customwas again recooled to -78° C.
10. customCO2 gas was bubbled in until the red color
11. temperatureto warm to 20° C.
12. customafter removal of the solvent, 0.1M HCL (50 mL)
13. additionwas added
14. extractionThe resulting mixture was extracted with EtOAc
15. washthis was then washed successively with 0.1M HCl, water, and dilute aqueous Na2CO3
16. dry with materialAfter drying (Na2SO4)
17. customthe solvent was removed under vacuum
18. customto leave an oil which
19. customwas purified by chromatography on Al2O3