Oxazole new world: A gold‐catalyzed intermolecular reaction of pyridine‐N‐aminides with ynamides can be used to prepare trisubstituted 1,3‐oxazoles with a variety of functional groups. This formal [3+2] cycloaddition employs robust conjugated N‐ylides as N‐nucleophilic N‐acyl nitrene equivalents for a highly chemoselective and regioselective addition across electron‐rich CC triple bonds.
Ynamides and ynol ethers undergo intermolecular gold-catalysed reaction with a nucleophilic oxidant to access metal-carbenoid reactivity patterns. A site-specific oxidation/1,2-insertion cascade is used for a general access to functionalised α,β-unsaturated carboxylic acid derivatives and vinylogous carbimates.
Scheme 4. Scope for the gold-catalyzed oxazole cycloaddition. [a] [a] Reaction conditions: 1(b-g) (1.5 equiv), 2(a-l) (1.0 equiv) and [Au-I] (5 mol %) in toluene (0.1 m) were reacted at 90 8C. Reactions were monitored by TLC and stopped after the time shown in parentheses. Yields refer to isolated product after column chromatography. [b] Contaminated with < 5 % of the 5-vinyloxazole from HBr elimination. TBDPS = tert-butyldiphenylsilyl.
Angewandte Chemie
9095
A site‐specific oxidation/1,2‐insertion cascade offers access to functionalized α,β‐unsaturated carboxylic ester and imide derivatives as well as vinylogous amides.
Intermolecular and Selective Synthesis of 2,4,5-Trisubstituted Oxazoles by a Gold-Catalyzed Formal [3 + 2] Cycloaddition. -Trisubstituted 1,3-oxazoles are smoothly prepared by the intermolecular reaction of pyridine-N-aminides with ynamides tolerating a variety of functional groups. In contrast, acyclic ethylimidate (VII) is obtained under similar conditions from ynol ether (VI). -(DAVIES*, P. W.; CREMONESI, A.; DUMITRESCU, L.; Angew. Chem., Int. Ed. 50 (2011) 38, 8931-8935, http://dx.doi.org/10.1002/anie.201103563 ; Sch. Chem., Univ. Birmingham, Edgbaston, Birmingham B15 2TT, UK; Eng.) -S. Adam
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.