1,3-Propanediol → 5'-chlorospiro[1,3-dioxane-2,3'-indol]-2'(1'H)-one

Participants

Reaction Steps

A mixture of 5-chloroisatin (5.00 g, 27.5 mmol), p-toluenesulfonic acid monohydrate (1.05 g, 5.5 mmol, 0.2 mole %) and 1,3 propanediol (6.04 mL, 83 mmol, 3 eq) in benzene (535 mL) was refluxed with a Dean Stark Trap for 7.5 hr. After cooling to room temperature the solution was decanted from the reaction mixture and concentrated The residue was washed with sat. aq. NaHCO3 (2×), brine (1×), dried over Na2SO4, filtered and concentrated. The crude product was purified on Biotage KP silica gel eluting with 70/30 Petroleum ether/EtOAc to give the title compound as a pale yellow solid (4.77 g, 72.5% ). A portion was dried at 42° C. in vacuo to give the analytically pure sample. Anal: Calc'd for C11H10ClNO3: C, 55.13; H, 4.21; N, 5.84. Found: C, 55.31; H, 4.34; N, 5.78. NMR (300 Mz, DMSO-d6): consistent. IR: consistent. MS: (ES−) m/z 238 [M−H]; one Cl pattern observed, consistent. m.p.: 184-185° C.

Provenance & Evidence