Gold‐catalyzed Cyclization of Non‐conjugated Ynone‐oxime Derivatives: Incorporation of Solvent Molecule

Abstract

Au ııı-promoted cyclization reaction of ynoneoxime derivatives furnished 4H-1,2-oxazine ring under mild reaction conditions. When an alcohol is present in the reaction media, it was attached to the oxazine ring by the second activation of cyclic intermediate with a gold catalyst. Cholesterol, propargyl alcohol, phenol, and some of the different alcohol derivatives with alkyl chain were bonded to the oxazine ring in good yields. While amine derivatives did not attach to the ring under optimized reaction conditions, the molecule with the thiol group deactivated the gold catalyst under the same reaction conditions and did not give any cyclic products. With the obtained cyclization protocol, 11 unknown oxazine derivatives were synthesized and characterized. The proposed cyclization mechanism was drawn according to the two independent control experiments, DFT optimization, and NBO charges.

A Method for Pyrrole Synthesis through Intramolecular Cyclization of γ-Alkynyl Oximes Promoted by SmI2

“…(3) Synthesis of 1o 24 To a solution of anhyd THF (0.9 mL) and anhyd Et 3 N (0.3 mL) were added 1-phenylpent-4-yn-1-one oxime (0.163 g, 1 mmol), Pd(OAc) 2 (5 mg), CuI (10 mg), and PPh 3 (20 mg). To the reaction mixture was added PhI (0.2 mL, 1 mmol).…”

“…(3) Synthesis of 1o [24] To a solution of dried THF (0.9 mL) and dried TEA (0.3 mL) was added 0.163 g (1 mmol) 1-phenylpent-4-yn-1-one oxime. 5 mg Pd(OAc)2, 10 mg CuI, and 20 mg PPh3.…”

“…Template for SYNTHESIS Thieme Yield 82%; white solid; Mp=57-58℃. (Z/E)-1-(4-methoxyphenyl) pent-4-yn-1-one oxime (1d) [24] Yield 66%; white solid; Mp=66-67℃. Yield 40%; white solid; Mp=95-96℃.…”

“…Yield 40%; white solid; Mp=95-96℃. (Z/E)-1-(thiophen-2-yl) pent-4-yn-1-one oxime (1l) [24] Yield 16%; white solid; Mp=105-106℃.…”

“…2-(2-methoxyphenyl)-5-methyl-1H-pyrrole (2q) [29] Yield 0.0150 g, 16%; pink solid; Mp=27-28℃. 2-(furan-2-yl)-5-methyl-1H-pyrrole (2s) [30] Yield 0.0192 g, 26%; green liquid; 1-phenylpent-4-yn-1-one (B) [24] white solid; Mp =72-73°C.…”