Convenient Synthesis of 3,5‐Disubstituted Isoxazoles

A Facile One-Pot Synthesis of 3,5-Disubstituted Isoxazole Derivatives Using Hydroxy (Tosyloxy) Iodobenzene

“…Reaction with 4‐nitrobenzaldehyde oxime (0.25 g, 1.50 mmol) and 4‐ethynyl anisole (0.39 mL, 3.00 mmol) afforded compound 12h (0.21 g, 49%) as a white solid, mp 173–175°C (lit : 172–175°C); 1 H NMR (300 MHz, DMSO‐ d 6 ): δ 8.36 (d, J = 8.7 Hz, 2H, phenyl), 8.06 (d, J = 8.7 Hz, 2H, phenyl), 7.81 (d, J = 8.7 Hz, 2H, phenyl), 7.04 (d, J = 8.7 Hz, 2H, phenyl), 6.79 (s, 1H, isoxazole), 3.90 (s, 3H, OCH 3 ); 13 C NMR (75 MHz, CDCl 3 ) δ 169.8, 162.4, 162.1, 148.8, 133.8, 127.6, 127.5, 127.0, 124.2 (2C), 123.6, 114.5 (2C), 114.2, 96.1, 55.4; HRMS (ESI+) calcd. for C 16 H 13 N 2 O 4 [M + H] + 297.0870, found 297.0872 (error 0.67 ppm); HPLC: retention time 6.08 min, purity 97.63% (method A).…”

Use of Solid-Supported Reagents towards Synthesis of 2-Arylbenzoxazole, 3, 5-Diarylisoxazole and 1, 3, 5-Triarylpyrazole

“…Our method depicts use of less toxic reagent as well as good yields of product. On the other side, to carry out aromatization of 2-pyrazoline and oxidative cyclization of phenylhydrazone, limited reports are there in the literature which include reagents like Pb(OAc) 4 [24], PhI(OAc) 2 [25], Pd/C [26] and Zr(NO 3 ) 4 [27]. Our method stands out to be more feasible compared to literature known methods due to its versatility in variety of substrates being subjected to oxidation with good yields of the product.…”

“…There are several routes by which 3,5-diaryl isoxazoles can be synthesized. The [5 + 0] route involving oxidative cyclization of α, β-unsaturated ketoximes using oxidizing agents like DDQ [21], MnO 2 [22], I 2 /KI in NaHCO 3 [23], are some of the few known. Our method depicts use of less toxic reagent as well as good yields of product.…”

Copper-catalyzed aerobic oxidative C–O bond formation for the synthesis of 3,5-disubstituted isoxazoles from enone oximes

“…Nonetheless, the latter methods commonly require the use of stoichiometric amounts of oxidants, such as TEMPO, hypervalent iodine, DDQ, metal salt and so on, which caused heavy burden to the environment. [41][42][43][44][45][46] It is no doubt that the catalyzed oxidation with pure oxygen or air as the oxidant is a green solution. Herein, we disclose a new copper(II)-catalyzed synthesis of 3,5-disubstituted isoxazoles from enone oximes through a C-H functionalization/C-O bond-forming process that uses oxygen as the terminal oxidant and water as the only direct waste product.…”