Palladium-Catalyzed Alkyne Insertion/Suzuki Reaction of Alkyl Iodides
作者:Brendan M. Monks、Silas P. Cook
DOI:10.1021/ja307761f
日期:2012.9.19
A palladium-catalyzed alkyne insertion/Suzuki reaction with unactivated alkyliodides is described. Under the reaction conditions, selective migratory insertion of alkynes avoids β-hydride elimination and provides a facile synthesis of stereodefined, tetrasubstituted olefins. The transformation offers broad substrate scope for both the alkyliodide and boron nucleophile. Mechanistic studies have revealed
Discovery of a Phosphine-Mediated Cycloisomerization of Alkynyl Hemiketals: Access to Spiroketals and Dihydropyrazoles via Tandem Reactions
作者:Jaideep Saha、Chris Lorenc、Bikash Surana、Mark W. Peczuh
DOI:10.1021/jo3001854
日期:2012.4.20
functionality (R2) on the cyclic keto enol ether, a rapid and facile dimerization occurs, giving spiroketal products. When the enone is substituted (i.e., R2 = Ph), the cyclic keto enol ether is sufficiently stable so that it can be isolated; it can then be further reacted in the same pot to provide the corresponding dihydropyrazoles. Both the spiroketal and dihydropyrazole products arise by a tandem reaction
An efficient Synthesis of Acetylenic ?- and ?-Hydroxy Ketones, ?- and ?-keto acids, and ?- diketones via addition of 1-alkinyllithium compounds to ?- and ?-lactones
作者:Christine Wedler、Hans Schick
DOI:10.1002/prac.19933350503
日期:——
2-Hydroxy-6-alkyn-5-ones 3, 1-hydroxy-5-alkyn-4-ones 4, and 1-hydroxy-6-alkyn-5-ones 5 are conveniently obtained in exellent yields through a highly selective monoaddition of an 1-alkynyllithium compound 2 to gamma-valerolactone (1 a), gamma-butyrolactone (1 b) or delta-valerolactone (1 c). They are oxidized by pyridinium dichromate or Jones reagent to the corresponding acetylenic 1,4-diketones 6, 4-oxo carboxylic acids 7, and 5-oxo carboxylic acids 8, respectively.
Palladium-Catalyzed Asymmetric Synthesis of 2-Alkynyl Oxacycles
作者:David S. B. Daniels、Amber L. Thompson、Edward A. Anderson
DOI:10.1002/anie.201105720
日期:2011.11.25
cyclizations of cyclic and acyclic propargylic carbonates give 2‐alkynyl oxacycles. The reactions proceed with very high stereoselectivity for both syn‐ and anti‐disubstituted furans and pyrans, and with exceptional regioselectivity. In addition, two‐directional cyclizations of bis‐propargylic carbonate substrates yield bifurans with complete stereocontrol for all diastereomers.