Compound 1c

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Compound data: 1H NMR

Compound data: 13C NMR

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

In an oven dried round bottom flask under an atmosphere of argon, 5-bromoindole (1 equiv.) was dissolved in a minimal amount of THF (commercial synthesis grade; 10 mL·g^-1). The flask was cooled to 0 ºC in an ice-water bath and potassium tert-butoxide (1.1 equiv.) was added portionwise. The mixture turned a slight yellow/orange color and was left to stir for 30 minutes. Still at 0 ºC, carbon disulfide (1.5 equiv.) was added dropwise via syringe addition. The mixture immediately turned a bright orange color and was left to stir for one hour at 0 ºC. After warming up to ambient temperature, THF was evaporated carefully on a rotary evaporator to a thick syrupy consistence. Toluene was added and evaporated to obtain a yellow solid residue. The residue was suspended in a 1:1 mixture of pentane and diethyl ether and stirred vigorously to obtain a fine suspension. The yellow solid was then filtered under a flow of argon, washed twice with a small amount of a 1:1 mixture of pentane and diethyl ether and further dried overnight under high vacuum to obtain the desired product as a yellow free flowing powder. This reaction has been performed on various scales (5 to 55 mmol of starting 5-bromoindole) with isolated yields ranging from 88 to 95%. Note: Once isolated, 1c is slightly hygroscopic and should therefore be protected from ambient humidity. It was typically stored in brown glass bottles in a desiccator. No degradation was detected over a 3-month period, as indicated by NMR analysis. ¹H NMR (400 MHz, d6-DMSO) δ 6.39 (d, J=3.5 Hz, 1H), 7.25 (dd, J= 9, 2.1 Hz, 1H), 7.68 (d, J=2.1 Hz, 1H), 8.69 (d, J= 3.5 Hz, 1H), 9.28 (d, J= 9 Hz, 1H) ¹³C NMR (101 MHz, d6-DMSO) δ 218.7 (C), 134.9 (C), 133.9 (C), 132.2 (CH), 124.9 (CH), 122.7 (CH), 120.0 (CH), 113.5 (C), 102.0 (CH) IR (thin film) ν 1744, 1438, 1354, 1292, 1204, 1174, 1065, 1000, 829, 724 cm^-1. HRMS (ESI negative): calculated for C₉H₅⁷⁹BrNS₂ (M): 269.9052, found 269.9044.