Abstract
Gold(I)-catalyzed intramolecular hydroamination of O- propargyl-N -Boc- hydroxylamine is reported. The present method provides a novel, catalytic, and mild
approach to 2,5-dihydroisoxazole derivatives. In addition, a mechanism of N-O cleavage
as a side reaction as well as desired cyclization is proposed.
Key words
2,5-dihydroisoxazoles - heterocycles - cyclizations - gold catalysis - carbenoids
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Representative Procedure for the Formation of 2d
1d (133 mg, 0.780 mmol) in CH2 Cl2 (4 mL) was added Au(PPh3 )Cl (1.9 mg, 3.9 µmol, 0.5 mol%) and AgOTf (1 mg, 3.9 µmol), and the mixture was stirred
for 2 h at r.t. After removal of solvent, the residual oil was purified by silica
gel flash chromatography to afford 2d as colorless oil (90.3 mg, 68%). 1 H NMR (400 MHz, CDCl3 ): δ = 6.60 (t, J = 2.2, 4.7 Hz, 1 H), 5.30 (td, J = 1.8, 4.7 Hz, 1 H), 5.03 (t, J = 2.2 Hz, 1 H), 1.54 (s, 9 H). 13 C NMR (100 MHz, CDCl3 ): δ = 151.0, 125.8, 103.2, 82.1, 75.0, 28.1. LRMS (EI): for C8 H13 NO3 [M+ ]: m/z = 171; for C7 H10 NO3 [M+ - Me]: m/z = 156; for C7 H13 NO [M+ - CO2 ]: m/z = 127; for C3 H5 NO [M+ - t -BuOCO + H]: m/z = 71. Anal. Calcd for C8 H13 NO3 : C, 56.13; H, 7.65; N, 8.18. Found: C, 56.16; H, 7.47; N, 8.14.
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