First Approach to the Frondosin C Ring System via a Tandem Cyclization/Claisen Rearrangement Sequence
摘要:
[GRAPHICS]A one-pot tandem 5-exo cyclization/Claisen rearrangement strategy is utilized as the key step in the straightforward construction of the tetracyclic ring system of frondosin C. This reaction is done under microwave irradiation in the presence of catalytic MeLi.
Lewis acid catalyzed cascade annulation of alkynols with α-ketoesters: a facile access to γ-spiroketal-γ-lactones
作者:Digambar A. Kambale、Sagar S. Thorat、Madhukar S. Pratapure、Rajesh G. Gonnade、Ravindar Kontham
DOI:10.1039/c7cc03668j
日期:——
A novel Lewisacidcatalyzed intermolecular cascade annulation of alkynols with α-ketoesters has been developed. This simple and efficient cascade annulation proceeds through a 5-exo-dig cyclization of alkynols followed by annulation with α-ketoester to provide a wide variety of unsaturated γ-spiroketal-γ-lactones (1,6-dioxaspiro[4.4]non-3-en-2-ones) related to many natural products.
Direct Catalytic Asymmetric Mannich Reactions for the Construction of Quaternary Carbon Stereocenters
作者:Barry M. Trost、Tanguy Saget、Chao-I (Joey) Hung
DOI:10.1021/jacs.6b01187
日期:2016.3.23
Mannich reaction using α-branched ketones as nucleophilic partners for the direct enantio- and diastereoselective construction of quaternary carbon stereocenters. The reaction can be run on a gram-scale with a low catalyst loading without impacting its efficiency. Moreover, the Mannich adducts can be further elaborated with complete diastereocontrol to access molecules possessing complex stereotriads.
Direct catalytic enantioselective amination of ketones for the formation of tri- and tetrasubstituted stereocenters
作者:B. M. Trost、J. S. Tracy、T. Saget
DOI:10.1039/c8sc00147b
日期:——
Herein, we report a Zn–ProPhenol catalyzed direct asymmetric amination reaction of unactivated aryl and vinyl ketones using di-tert-butyl azodicarboxylate as a cheap and practical electrophilic nitrogen source. Importantly, this methodology works with both α-branched and unbranched ketones for the construction of tri- and tetrasubstituted N-containing stereocenters. The reaction can be run at gram-scale
tethered with a vinyl azide group undergo a Schmidt-hydrolysis sequence to give secondary lactams bearing a ketone side chain. Secondary lactams are obtained in a regioselective manner that is not possible in a conventional Schimdt reaction. In addition to the well-documented C-2 nucleophilicity, the N nucleophilicity of vinyl azide disclosed in this work opens a new direction for reaction invention involving
First Approach to the Frondosin C Ring System via a Tandem Cyclization/Claisen Rearrangement Sequence
作者:Isamir Martínez、Philip E. Alford、Timo V. Ovaska
DOI:10.1021/ol050144o
日期:2005.3.1
[GRAPHICS]A one-pot tandem 5-exo cyclization/Claisen rearrangement strategy is utilized as the key step in the straightforward construction of the tetracyclic ring system of frondosin C. This reaction is done under microwave irradiation in the presence of catalytic MeLi.