Rhodium-Catalyzed, Enantioselective Hydroacylation of <i>ortho</i>-Allylbenzaldehydes
作者:Kirsten F. Johnson、Adam C. Schmidt、Levi M. Stanley
DOI:10.1021/acs.orglett.5b02559
日期:2015.10.2
The development of a rhodiumcatalyst for endo- and enantioselective hydroacylation of ortho-allylbenzaldehydes is reported. A catalyst generated in situ from [Rh(COD)Cl]2, (R)-DTBM-SEGPHOS, and NaBARF promotes the desired hydroacylation reactions and minimizes the formation of byproducts from competitive alkene isomerization and ene/dehydration pathways. These rhodium-catalyzed processes generate
bicyclic core structures with up to three stereocenters within a single step. Herein, this concept is combined with the chemistry of chiral Brønsted acid bound ortho-quinonemethideimines to generate a range of interesting fused tetrahydroquinolines in a diastereo- and enantioselective manner.
Visible-light induced generation of bifunctional nitrogen-centered radicals: a concise synthetic strategy to construct bicyclo[3.2.1] octane and azepane cores
A photocatalytic tandem cyclization of o-alkenylbenzaldehydes using pyridinium salts as the amination reagent is described. A variety of valuable seven-membered nitrogenous heterocyclic skeletons are prepared in modest to excellent yields in concise one-step. This transformation features mild reaction conditions and exceptional functional group tolerance. In addition, combining control experiments and density functional theory (DFT) calculations on the mechanism can explain the reaction selectivity.
A Synthesis of 6-Azabicyclo[3.2.1]octanes. The Role of <i>N</i>-Substitution
作者:Aravinda B. Pulipaka、Stephen C. Bergmeier
DOI:10.1021/jo702444c
日期:2008.2.1
The intramolecular cyclization reactions of aziridines with π-nucleophiles can be a useful route to a number of heterocyclic and carbocyclic ringsystems. We were particularly interested in the use of this cyclization reaction for the synthesis of 6-azabicyclo[3.2.1]octanes. We report here the development of a new synthesis of the aziridine necessary for the aziridine−π-nucleophile cyclization. We
Noncanonical Cation−π Cyclizations of Alkylidene β-Ketoesters: Synthesis of Spiro-fused and Bridged Bicyclic Ring Systems
作者:Dylan E. Parsons、Alison J. Frontier
DOI:10.1021/acs.orglett.9b00094
日期:2019.4.5
conditions employed, it is possible to achieve selective synthesis of the three different types of products, including 1-halo-3-carbomethoxycyclohexanes, spiro-fused tricyclic systems, and [4.3.1] bridged bicyclicringsystems. All three reactions begin with 6-endo addition of an olefin to the alkylidene β-ketoester electrophile, followed by one of three different cation capture events.