“…The compatibility of phosphine based ligands being capable of serving in oxidative allylic alkylations led to the development of an
asymmetric version as well (eq 85). 85 This example is the only reported asymmetric allylic alkylation of any kind involving allylic C-H activation.…”
“…The compatibility of phosphine based ligands being capable of serving in oxidative allylic alkylations led to the development of an
asymmetric version as well (eq 85). 85 This example is the only reported asymmetric allylic alkylation of any kind involving allylic C-H activation.…”
“…[3] Alternatively, chiral palladium/phosphoramidite catalysts for allylic C–H functionalizations have demonstrated modest enantioselectivity (avg. 75% ee, 1 example ≥90% ee [4] , avg. 83% ee, 2 examples at 90% ee [5] ), limited olefin scope (generally doubly activated C–H bonds) and high sensitivity to O 2 .…”
mentioning
confidence: 99%
“…83% ee, 2 examples at 90% ee [5] ), limited olefin scope (generally doubly activated C–H bonds) and high sensitivity to O 2 . [4,5] We hypothesized the ideal catalytic platform would utilize an oxidatively stable, chiral ligand capable of promoting both C–H cleavage and functionalization, thus circumventing the challenges of serial ligand catalysis.…”
mentioning
confidence: 99%
“…Gratifyingly, broad aromatic substitution is tolerated, with both electron-rich substrates (entries 2b , 2c , 2d ) and electron-deficient substrates (entries 2e , 2f , 2g , 2h , 2i ) furnishing the desired products in good yields and high enantioselectivities. Broad tolerance for electronic substitution on aryls has not been previously shown for other asymmetric allylic C–H methods, which show either decreased enantioselectivity for electron-rich aryl moieties, [4] or inconsistent trends for aryl tolerance. [5] Bromide and chloride substitution is well tolerated, and these groups serve as handles for further manipulation (products 2e , 2h ).…”
The enantioselective synthesis of isochroman motifs has been accomplished via Pd(II)-catalyzed allylic C–H oxidation from terminal olefin precursors. Critical to the success of this goal was the development and utilization of a novel chiral aryl sulfoxide-oxazoline (ArSOX) ligand. The allylic C–H oxidation reaction proceeds with the broadest scope and highest levels asymmetric induction reported to date (avg. 92% ee, 13 examples ≥90% ee)
“…The stereochemical complexity of medicinally important compounds is increasing, and recent studies have suggested that compounds containing increased numbers of sp 3 carbon centers are more successful through clinical trials. 1 Although C-H bond functionalization reactions have the potential to alter the strategies by which these compounds are prepared, 2 a major challenge encountered when developing C-H bond functionalization reactions is the control of absolute and relative stereochemistry.…”
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 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 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.