Lawesson's reagent → tert-butyl (S)-2-phenyl-1-thiocarbamoylethylcarbamate

Participants

Reaction Steps

To a solution of #12 (14.060 g, 53.192 mmol, 1 eq.) in tetrahydrofuran (180 mL, 0.296 M), was added 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-dithione (Lawesson's reagent) (12.70 g, 31.40 mmol, 0.59 eq.) and the reaction was refluxed for 90 minutes. The reaction was cooled to room temperature and quenched by addition of saturated aqueous sodium bicarbonate solution. The mixture was extracted twice with ethyl acetate and the combined organic layers were dried over sodium sulfate, filtered, and concentrated in vacuo. The residue was dissolved in ethyl acetate, concentrated in vacuo onto silica and purified by silica gel chromatography (Gradient: 0% to 100% ethyl acetate in heptane), affording #13 (11.50 g, 77%) as a white solid. LC-MS: m/z 279.4 [M−H+], 225.2 [(M−2-methylprop-1-ene)+H+], 181.2 [(M−Boc)+H+]; 1H NMR (400 MHz, DMSO-d6), presumed to be a mixture of rotamers, major rotamer: δ 9.60 (br s, 1H), 9.19 (br s, 1H), 7.23-7.32 (m, 5H), 6.82 (d, J=8.8 Hz, 1H), 4.44 (ddd, J=9.4, 9.1, 4.4 Hz, 1H), 3.00 (dd, J=13.7, 4.5 Hz, 1H), 2.79 (dd, J=13.6, 9.9 Hz, 1H), 1.29 (s, 9H).

Provenance & Evidence