313995-41-4Relevant academic research and scientific papers
Enantioselective functionalization of allylic C-H bonds following a strategy of functionalization and diversification
Sharma, Ankit,Hartwig, John F.
, p. 17983 - 17989 (2014/01/06)
We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by the catalytic diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S, or C-C bond at the allylic position in good yield with a high branched-to-linear selectivity and excellent enantioselectivity (ee ≤97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated.
The stereoselective preparation of substituted pyrrolidines using titanium- And zirconium-mediated diene metallabicyclisation methodology: The total synthesis of (-)-α-kainic acid
Campbell, Andrew D.,Raynham, Tony M.,Taylor, Richard J. K.
, p. 3194 - 3204 (2007/10/03)
Zirconium- and titanium-mediated diene metallabicyclisation-elimination-functionalisation have been compared, contrasted and utilised for the preparation of 3,4-disubstituted and 2,3,4-trisubstituted pyrrolidines in high yield and excellent stereoselectivity. The zirconium-mediated methodology has been employed as the key step in a partial synthesis of (-)-α-kainic acid starting from D-serine, but the key metallabicyclisation sequence proceeded with poor stereocontrol. By contrast, the total synthesis of (-)-α-kainic acid starting from L-serine was accomplished using a titanium-mediated cyclisation sequence which proceeded with excellent stereocontrol. Novel kainoids and piperidines are also reported. The Royal Society of Chemistry 2000.
