Asymmetric synthesis of 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1- dioxides catalyzed by scandium(III)-inda-Pybox

Recent Advances in the Creation of Asymmetric Carbon Centre(s) by Generation of Carbon‐Heteroatom Bond(s) Using Metal‐Pybox Complexes

“…Zhou and co‐workers reported that the presence of Sc(III)‐pybox(L 14 ) complex efficiently catalyzed the asymmetric synthesis of biologically potent 3,4‐dihydro‐2H‐1,2,4‐benzothiadiazine‐1,1‐dioxides (DHBDs) (Scheme ) . The reaction proceeded via intermolecular condensation to yield the intermediate imine followed by intramolecular asymmetric amine addition sequences of 2‐aminobenzene sulfonamides and aldehydes.…”

Recent developments in enantioselective lanthanide-catalyzed transformations

“…To establish that precatalyst 23 was amenable to different RE/M combinations, the asymmetric aza-Michael addition of methylhydroxylamine 31 to chalcones 12 was investigated [20]. Indeed, the use of yttrium complex 32 as precatalyst of the corresponding heterobimetallic Y/Li/BINOL active catalyst at only 3 mol% of catalyst loading in these reactions allowed the corresponding aza-Michael products 33 to be obtained in both excellent yields and enantioselectivities of [88][89][90][91][92][93][94][95][96][97]respectively (Scheme 9).…”

“…In this context, the same reactions were performed in the presence of secondary amine ligand 67 prepared by reduction of ligand 64 by treatment with NaBH 4 . Under these related reaction conditions, the cycloaddition of aryl enones 65 with alkyl enones 29a-c afforded the corresponding cyclobutanes 68 in moderate yields (49-80%), low to moderate diastereoselectivities (20-64% de) albeit with high to excellent enantioselectivities of [84][85][86][87][88][89][90][91][92][93][94][95][96][97]. Notably, using ligand 67 instead of ligand 64 allowed a complementary diastereoselectivity.…”

“…Catalyst 85, generated through self-assembly performed in the presence of MWNT, gave the optimal result in comparison with that was self-assembled before adding MWNT. When 1 mol% of catalyst 85 was used to promote the Henry reaction of aldehydes 77h-l with nitroalkanes 9a-c, it led to the corresponding products 86a-g as major antidiastereomers in moderate to quantitative yields (52-99%), good to excellent anti/syn ratios of 83:17 to >98:2, and uniformly high enantioselectivities of [87][88][89][90][91][92][93][94][95][96][97][98][99]. This reusable confined catalyst exhibited higher catalytic efficiency that the corresponding unconfined catalyst.…”

“…In the past decade, a number of chiral scandium catalysts have been successfully applied to various asymmetric domino reactions including multicomponent ones, such as three-component Mannich-type reactions [87], three-component aza-Diels-Alder reactions [88], and threecomponent allylation reactions [89] among others. A more recent example was reported by Zhou et al, dealing with asymmetric domino imine formation/intramolecular amination reaction of aldehydes 77 with 2-aminobenzenesulfonamide 153 to yield the corresponding chiral 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxides 154 [90]. These products constitute an important class of substances with a wide range of biological activities.…”