期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 134, 期 42, 页码 17412-17415出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja307948m
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资金
- NIH [R01 GM084254]
- NSF [CAREER CHE-0969157, PIRE-ECCI OISE-0968399]
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1040541] Funding Source: National Science Foundation
- Office Of Internatl Science &Engineering
- Office Of The Director [968399] Funding Source: National Science Foundation
2,4-Oxazole is an important structural motif in various natural products. An efficient modular synthesis of this structure has been achieved via a [3 + 2] annulation between a terminal alkyne and a carboxamide using a gold-catalyzed oxidation strategy. The postulated reactive intermediate, a terminal alpha-oxo gold carbene, previously known to be highly electrophilic and hence unlikely to be trapped by stoichiometric eternal nucleophiles, is coerced to react smoothly with the carboxamide en route to the oxazole ring by a P,N- or P,S-bidentate ligand such as MorDalPhos; in stark contrast, often-used ligands such as monodentate phosphines and N-heterocyclic carbenes are totally ineffective. The role of these bidentate phosphines in this reaction is attributed to the formation of a tricoordinated gold carbene intermediate, which is less electrophilic and hence more chemoselective when reacting with nucleophiles. The success in using bidentate phosphine ligands to temper the reactivities of in situ-generated gold carbenes is likely to open many new opportunities to apply oxidative gold catalysis to the development of novel methods, and the implication of tricoordinated gold intermediates in homogeneous gold catalysis should stimulate further advances in gold catalysis.
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