Cobalt-Catalyzed Cross-Coupling Reactions of Heterocyclic Chlorides with Arylmagnesium Halides and of Polyfunctionalized Arylcopper Reagents with Aryl Bromides, Chlorides, Fluorides and Tosylates
A range of aromatic organocopper or organomagnesium compounds undergo smooth cross-coupling reactions with aryl bromides, chlorides, fluorides and tosylates, leading to polyfunctionalized aromatics or heterocycles in the presence of cobalt salts (5-7.5 mol%) as catalysts. Very mild reaction conditions are needed and, in the case of cross-coupling with organocopper compounds, Bu4NI (1 equiv) and 4-fluorostyrene (20 mol%) are essential as promoters for successful couplings.
Oxidative heterocoupling between two Grignardreagents RMgX and R′MgX is made possible by manganese catalysis with O2 as an oxidant. This procedure, development of which was based on mechanistic analysis of the corresponding homocoupling reaction, can be steered towards the heterocoupling product at the expense of the homocoupling products by judicious choice of the R and R′ groups (see examples).
Mono- and Biscouplings Using Triarylbismuths for the Atom-Efficient Arylations of Functionalized Furans under Palladium Catalysis
作者:Maddali Rao、Dheeraj Awasthi、Jalindar Talode
DOI:10.1055/s-0032-1316567
日期:2012.8
Palladium-catalyzed cross-coupling reactions of functionalized bromofurans with triarylbismuths have been described for the atom-economic synthesis of functionalized arylfuran systems. The coupling reactions using triarylbismuths with various 2-bromofurans and 2,5-dibromofuran underwent smoothly to afford the corresponding 2-arylfurans and 2,5-diarylfurans in high yields in a short reaction time (one
can be arylated at the α-position in moderate to good yields. Mechanistic studies demonstrate that the reaction proceeds via a CMD pathway, with C–Hbondactivation as the rate-determining step. Furthermore, the scalability and applicability in the synthesis of a drug molecule exemplify the utility of this protocol.
Triflic Acid-Catalyzed Cycloisomerization Reactions of Donor–Acceptor Cyclopropanes: Access to Alkyl 5-Arylfuran-2-carboxylates
作者:Yuequan Zhu、Panpan Xu、Yuefa Gong
DOI:10.1021/acs.joc.6b00161
日期:2016.6.3
A direct synthetic strategy starting from alkyl 1-alkoxy-2-aroylcyclopropanecarboxylates was developed for the construction of alkyl 5-arylfuran-2-carboxylates. These donor acceptor cyclopropanes smoothly undergo a simple ring opening reaction or/and cycloisomerization reaction in the presence of acid at room temperature;, which greatly depends on the properties of the acid used in the experiment, Alkyl 5-arylfuran-2-carboxylates were afforded in high yields in triflic acid, whereas alkyl 2,5-dioxo-5-phenylpentanoate became the major product in other protic acids and Lewis acids.