Palladium catalysed cross-coupling of (fluoroarene)tricarbonylchromium(0) complexes
作者:René Wilhelm、David A. Widdowson
DOI:10.1039/b006576p
日期:——
(Fluoroarene)tricarbonylchromium(0) complexes were found to undergo Suzuki and Stille cross-coupling reactions to form functionalised biaryl and styrene complexes in up to 87 and 52% yields, respectively. The Suzuki reactions were optimal with dipalladium tris(dibenzylideneacetone)–trimethylphosphine–caesium carbonate in DME at reflux. The Stille reactions were optimal with dipalladium tris(dibenzylideneacetone)–trimethylphosphine–caesium fluoride in DME at reflux and neither was adversely affected by a methoxy group on the complexed ring. The Suzuki reaction tolerated a chloro group on the arylboronic acid ring but not a bromo group.
A strategy for assembling biaryls linked through a medium‐sized ring is herein presented. π‐Complexation of fluoroarenes to chromium tricarbonyl activates the molecule towards both C−H activation and nucleophilic aromatic substitution without covalently altering the molecular connectivity of the arene. The construction of bridged biaryl molecules with 6–10‐membered core rings is achieved through a
Arene–Metal π-Complexation as a Traceless Reactivity Enhancer for C–H Arylation
作者:Paolo Ricci、Katrina Krämer、Xacobe C. Cambeiro、Igor Larrosa
DOI:10.1021/ja405936s
日期:2013.9.11
approach where C-H arylation is made possible without altering the connectivity of the arene via π-complexation of a Cr(CO)3 unit, greatly enhancing the reactivity of the aromatic C-H bonds. We apply this approach to monofluorobenzenes, highly unreactive arenes, which upon complexation become nearly as reactive as pentafluorobenzene itself in their couplings with iodoarenes. DFT calculations indicate that
zed asymmetric SNAr reactions provide unique contribution to the catalyticasymmetric α‐arylations of carbonyl compounds to produce biologically active α‐aryl carbonyl compounds, the electrophiles were limited to arenes bearing strong electron‐withdrawing groups, such as a nitro group. To overcome this limitation, we examined the asymmetric SNAr reactions of α‐amino acid derivatives with arene chromium
尽管相转移催化的不对称S N Ar反应为羰基化合物的催化不对称α-芳基化反应产生了生物活性的α-芳基羰基化合物做出了独特贡献,但亲电试剂仅限于带有强吸电子基团的芳烃,例如硝基。为了克服这一局限性,我们研究了α-氨基酸衍生物与衍生自氟代芳烃的芳烃铬配合物(包括含给电子取代基的芳烃铬配合物)的不对称S N Ar反应。联萘改性的手性相转移催化剂可有效地促进芳基化反应,从而生成相应的α,α-二取代的α-氨基酸,其中包含具有高对映选择性的各种芳族取代基。