Hydrochloric Acid → tert-Butyl 1H-pyrrol-1-ylcarbamate

Participants

Reaction Conditions

Reaction Steps

A flask (fitted with a Dean-Stark trap) containing a stirred solution of tert-butylcarbazate (100, 0.757 mol), 2,5-dimethoxytetrahydrofuran (108 g, 0.832 mol) and 2N HCl (10 mL) in 1,4-dioxane (700 mL) was heated under nitrogen at 90° C. As the reaction progressed over several hours, the solution changed from pale yellow to orange and began to reflux. The reaction was monitored by the amount of distillate collected in the Dean-Stark trap (primarily CH3OH, 2 moles/1 mole reagent). As methanol collection approached the theoretical amount (50 mL), a sample was analyzed by TLC (silica gel, 1:3 EtOAc/hexane, ninhydrin stain) to confirm reaction completion. Heating was shut off and the reaction was allowed to cool somewhat before adding saturated, aq sodium bicarbonate solution (˜25 mL) to neutralize the hydrochloric acid. The quenched mixture was filtered through a sintered-glass funnel and concentrated in vacuo to leave an orange, semi-solid residue. The residue was suspended in diethyl ether (minimum volume) and the nearly colorless solids were collected by suction filtration, washed with hexane and air-dried to afford 60.2 g (40%) of product. A second crop (yellow-tan solids) from the mother liquors was isolated: 29.0 g (19%). 1H-NMR (CD3OD): δ10.23 (br s, 1H), 6.66 (t, 2H, J=2.2 Hz), 5.94 (t, 2H, J=2.2), 1.42 (s, 9H); MS: GC/MS (+esi): m/z=182.9 [MH]+

Provenance & Evidence