Gold-Catalyzed Radical-Involved Intramolecular Cyclization of Internal N-Propargylamides for the Construction of 5-Oxazole Ketones

Abstract

An expedient strategy for the synthesis of 5-oxazole ketones was developed via homogeneous gold catalysis with 4-MeO-TEMPO as an oxidant. The desired 5-oxazole ketones were achieved in decent yields with an excellent functional group compatibility under mild conditions. The current protocol also represents the first example for merging a gold catalyst and radical chemistry in one-pot synthesis with internal N-propargylamides.

tert‐Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis

“…This methodology shows excellent functional group tolerance under mild conditions. The present protocol was equally successful for heterocyclic and aliphatic propagylamides and the corresponding products were obtained in good to moderate yields (Scheme ) …”

“…Synthesis of functionalizedo xazoles from N-propargylamides using TBN. (147). The remarkablef eatures are transition-metal free, wide functional group tolerance, mild condition, and moderate to good reaction yields together with the incorporation of an amide functionality.T his method continues via ar eaction sequence of diazotization, followed by a nucleophilic addition of the alkyne to the diazonium ion to generate vinyl cation, nitrile addition to the intermediary vinyl cation and finally hydrolysis resultingi nt he incorporation of two new CÀNb onds (Scheme 110).…”

“…The present protocolw as equally successfulf or heterocyclic and aliphatic propagylamides and the corresponding products were obtained in good to moderate yields (Scheme 117). [147] Based on the control experiments and literature precedents ap lausible mechanism was proposed. Initially,A uc atalyzed cyclization of (155) During their studies on the steroidc hemistry,B arton et al disclosed an ovel method for the introductiono fa no xime functionality to an unactivated -Me group using ap hotolysis reactiono fn itrite compounds.…”

Visible‐Light‐Mediated Photocatalytic Synthesis of 2‐Substituted Oxazole‐5‐carbaldehydes Promoted by Benzeneseleninic Acid

“…of t BuONO as oxidant, under N 2 atmosphere and thermal conditions (Scheme 1). [15] Benzeneseleninic acid derivatives 5, which can be easily prepared under mild conditions, besides to be a bench stable, inodorous and easy to handle reagent, have been quietly explored as a Se-based electrophilic species, [16] while their use in oxygen transfer reactions, and other oxidation processes is well stablished. [13a,17] In this context, we recently developed a strategy to construct 3-selanylindoles and 4-selanylanilines selectively, through a SEAr process, employing arylseleninic acids as selenium source, under thermal condition.…”

Synthesis of Furoxans and Isoxazoles via Divergent [2 + 1 + 1 + 1] Annulations of Sulfoxonium Ylides and tBuONO

“…t BuONO has emerged as a brilliant nitrogen source to streamline synthesis of N-heterocycles in synthetic chemistry . As part of our ongoing interest in t BuONO and carbene chemistry, herein we report a novel [2 + 1 + 1 + 1] annulation reaction involved of multiple molecules of sulfoxonium ylides for the divergent synthesis of furoxans and isoxazoles using sulfoxonium ylides as carbene precursors and t BuONO as the nitrogen source (Scheme b).…”