Mild and Functional Group Tolerant Method for Tandem Palladium-Catalyzed Carbocyclization-Coupling of ε-Acetylenic β-Ketoesters with Aryl Bromides and Chlorides
作者:Wojciech Chaładaj、Sylwester Domański
DOI:10.1002/adsc.201600175
日期:2016.6.2
report a new protocol for the annulative difunctionalization of acetylenes via tandem carbocyclization–coupling of ε‐acetylenic β‐ketoesters with aryl and heteroaryl bromides and chlorides catalyzed by the palladium species derived from an air‐ and moisture‐stable palladacyclic precatalyst. In the tandem process, the palladiumcomplex combines appropriate carbophilic Lewis acidity and redox activity to catalyze
Tandem Palladium-Catalyzed 6-<i>exo</i>-<i>dig</i> Oxocyclization Coupling of δ-Acetylenic β-Ketoesters with Aryl Bromides and Chlorides: Route to Substituted Dihydropyrans
We report an efficient and functional group-tolerant method for the synthesis of substituted dihydropyrans, based on tandem Pd-catalyzed cyclization/coupling of δ-acetylenic β-ketoesters with aryl halides. The reaction proceeds cleanly through 6-exo-dig oxocyclizaton mode, delivering products with very good yields and complete control of regio- and stereoselectivity. Due to mild conditions, the transformation
W(CO)5(L)-Catalyzed Cyclization of α-Alkynyl-β-dicarbonyl Derivatives: Synthesis of Methylenelactones, Furans, and Methylenecyclopentanes
作者:Sunggak Kim、Xiangjian Meng
DOI:10.1055/s-0032-1316536
日期:2012.8
W(CO)(5)(L)-Catalyzed cyclization of alpha-alkynyl-beta-keto acids, keto esters, and diketones provides methylenelactones, furans, and methylenecyclopentanes via 5-exo-dig cyclization. Also, the present approach can be further applied to 5-endo-dig cyclization.
“Silver Effect” in Gold(I) Catalysis: An Overlooked Important Factor
作者:Dawei Wang、Rong Cai、Sripadh Sharma、James Jirak、Sravan K. Thummanapelli、Novruz G. Akhmedov、Hui Zhang、Xingbo Liu、Jeffrey L. Petersen、Xiaodong Shi
DOI:10.1021/ja303862z
日期:2012.5.30
Clear experimental evidence from X-ray photoelectron spectroscopy and P-31 NMR spectroscopy has been obtained for the first time to confirm that the combination of Ag+ cation with [L-Au](+) results in the formation of different complexes in solution. Re-evaluation of literature-reported gold-catalyzed reactions revealed a significant difference in the reactivities with and without silver. In extreme cases (more than "rare"), the conventional [L-Au](+) catalysts could not promote the reaction without the presence of silver. This investigation has therefore revealed a long-overlooked "silver effect" in gold catalysis and should lead to revision of the actual mechanism.
Group VI metal-promoted endo-carbocyclizations via alkyne-derived metal vinylidene carbenes
作者:Frank E. McDonald、Timothy C. Olson
DOI:10.1016/s0040-4039(97)10007-7
日期:1997.11
The molybdenum-promoted cycloisomerization of terminal alkynes tethered to beta-dicarbonyl nucleophiles is described, providing a novel synthesis of 1,1-disubstituted-2-cyclopentenes. (C) 1997 Elsevier Science Ltd.