Side arm modified chiral bisoxazoline ligands: Recent development and prospect in asymmetric catalysis

Copper-catalyzed enantioselective diyne cyclizationviaC(sp2)–O bond cleavage

“…However, employing several typical chiral BOX ligands L2–L6 led to diminished yields and enantioselectivities ( Table 3 , entries 2–6). In view of the fact that BOX ligands could be readily modified with the side-arm strategy established by Tang's group, 16 we attempted to alter the dibenzyl group of the BOX ligand. Gratifyingly, the enantioselectivity was significantly improved by employing 3,5-diethyoxyl benzyl-substituted BOX ligand L14 after a large amount of explorations ( Table 3 , entries 7–17), and the desired chiral chromeno[3,4- c ]pyrrole (+)-2a was delivered in 82% yield with 92% ee ( Table 3 , entry 14).…”

Strategies and Methods for the Catalytic Asymmetric Synthesis of Benzofuran/Benzopyran Fused Acetals: A Review

“…It is noteworthy that, improvement on both stereoselectivity and reactivity could be made by using steric hindered side arm modified BOX (SaBOX) ligand L2. [17] Based on their previous work, the authors proposed the possible transition state TS-2 as shown in Scheme 4. Chiral copper(II) complex prefers to coordinate to the methyl quinone carboxylate via bidentate coordination mode which leaves the Si face of methyl quinone carboxylate open for nucleophile attack by the γ-chromenes.…”

“…Additionally, in a similar [3+2] annulation manner, Wang and coworkers described a highly efficient procedure for the synthesis of benzofurochromane skeletons 7 from γ‐chromenes 6 with quinones 1 under chiral SaBOX/copper(II) catalyst system. It is noteworthy that, improvement on both stereoselectivity and reactivity could be made by using steric hindered side arm modified BOX (SaBOX) ligand L2 [17] . Based on their previous work, the authors proposed the possible transition state TS‐2 as shown in Scheme 4.…”

Catalytic Regio- and Enantioselective Boracarboxylation of Arylalkenes with CO2 and Diboron

“…Because of our group’s long-lasting interest in asymmetric catalysis, we would like to report our discovery of an efficient catalytic protocol for the enantioselective synthesis of boron-functionalized α-carboxylic acid derivatives from readily available alkenes and CO 2 (Scheme C). More significantly, various enantioenriched carboxylic acids with α-chiral all-carbon quaternary centers could also be procured in good yields, high functional group tolerance, and exceptional ee.…”