Lawesson's reagent → N-(3-Chloro-4-fluorophenyl)-4-[(triisopropylsilyl)oxy]methyl-1,2,5-oxadiazole-3-carbothioamide

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Reaction Steps

Into a round bottom flask was placed a solution of N-(3-chloro-4-fluorophenyl)-4-[(triisopropylsilyl)oxy]methyl-1,2,5-oxadiazole-3-carboxamide (4.1 g, 9.5 mmol) in anhydrous toluene (79 mL) under N2. 2,4-Bis(4-methoxyphenyl)-2,4-dithioxo-1,3,2,4-dithiadiphosphetane (7.7 g, 19 mmol) was added while stirring at ambient temperature. After addition, the resulting suspension was stirred and heated at 100° C. for 20 hrs. A considerable amount of solid precipitate was filtered off while the reaction was still hot, which was residual Lawesson's reagent. The liquid was then concentrated to give a yellow oil which was dissolved in chloroform and loaded onto a 330 g silica column eluting with 25% ethyl acetate/hexane to yield the desired product (3.31 g, 78%). 1H NMR (400 MHz, DMSO-d6) δ: 12.87 (s, 1H), 7.8 (ddd, J=8.9, 4.3, 2.7 Hz, 1H), 8.21 (dd, J=6.8, 2.7 Hz, 1H) 7.55 (dd, J=9.0, 9.0 Hz, 1H), 5.14 (s, 2H), 1.07 (m, 3H), 0.97 (d, J=7.0, 18H); (M+H)+: m/z=444.134.

Provenance & Evidence