Reaction Steps
A mixture of 31 (79 mg, 0.19 mmol) and trimethyloxonium tetrafluoroborate (105 mg, 0.71 mmol) in CH2Cl2 (5 mL) was stoppered and stirred at 20 C for 4 days. Water was added and the mixture stirred until most of the oily solid dissolved. The separated organic layer was dried (Na2SO4) and evaporated, dry column chromatography, eluting with EtOAc/petroleum ether (1:2), gave recovered starting material (24 mg, 30%). The aqueous phase was combined with the remaining oily solid, evaporated, and the residue extracted with MeOH. The resulting crude ammonium salt was converted to the chloride form by ion exchange chromatography on Dowex 50 WX8 resin (1.5 mL), loading the sample in MeOH:water (1:1) and washing until the eluate was neutral, then eluting with 1:1 MeOH:2N HCl (10 mL) followed by MeOH.backslash.4N HCl (1:1) (10 mL). The combined eluate was evaporated to give 3-(chloromethyl)-6-[N,N-dimethyl-N-(4-nitrobenzyl)-ammonio]-1-(methanesulfonyl)indoline chloride (11) as a white foam (87 mg). 1H NMR (CD3OD) a 8.17 (d, J=8.2 Hz, 2 H, ArH), 7.63 (br d, J=8.3 Hz, 1 H, H-4 or 5), 7.57 (br d, J=8.3 Hz, 1 H, H-4 or 5), 7.51 (s, 1 H, H-7), 7.41 (d, J=8.2 Hz, 2 H, ArH), 5.22 (s, 2 H, NCH2Ar), 4.32-4.25 (m, 1 H), 4.06-4.01 (m, 2 H), 3.96-3.93 (m, 2 H), 3.75 (s, 6 H, NMe2), 3.02 (s, 3 H, NSO2CH3). 13C NMR a 150.7, 146.0, 145.8, 136.1, 135.7 (C-6,8,9,1,4), 135.3, 124.8 (C-2 and 6, 3 and 5), 128.2, 117.9, 107.6 (C-4,5,7), 73.1 (NCH2Ar), 55.3 (C-2), 54.6 (NMe2), 47.8 (CH2Cl), 42.8 (C-3), 36.4 (SO2CH3).
