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A chiral Lewis acid-catalyzed enantioselective formal [2 + 2 + 2] cycloaddition of 1,3,5-triazinanes with azlactones or β,γ-unsaturated pyrazole amides was developed to synthesize chiral tertiary/quaternary tetrahydropyrimidin-4-one derivatives with good yields and enantioselectivities. Two competitive reaction pathways were proposed based on experiments. [ABSTRACT FROM AUTHOR]

Several unique chiral 3,4-dihydro-2H-pyrrole-2-thiones were made readily available by carrying out, in each case, a chiral-Mg(OTf)2/N,N′-dioxide-complex-promoted formal [2+1+2] cycloaddition in the presence of tetraethylenediamine. Control experiments revealed that in situ-generated ammonium thiocyanate was crucial for maintaining high enantioselectivity through its inhibition of the HNCS-induced racemization of the products. [ABSTRACT FROM AUTHOR]

Catalytic enantioselective [4+3] cycloaddition reaction between o-quinone methides and oxiranes was achieved by using a chiral N,N′-dioxide/TbIII complex as the catalyst, affording medium-sized hydrodioxepine derivatives in high yields (up to 99%) with good to excellent diastereo-(up to 94 : 6 dr) and enantioselectivities (up to 97% ee). The topographic steric maps and distribution of the buried volume (% VBur) of the catalysts via Cavallo's SambVca 2 tool were collected to effectively represent the chiral pocket of metal complexes of chiral N,N′-dioxides. [ABSTRACT FROM AUTHOR]

The chiral amide–guanidine-catalyzed asymmetric formal [3+2] cycloaddition of isatogens with azlactones is presented. This strategy provided a facile and feasible route to chiral indolin-3-one derivatives bearing two contiguous tetrasubstituted stereocenters in moderate to good yields with high diastereoselectivities and enantioselectivities. A possible working mode was proposed to elucidate the chiral control of the process. [ABSTRACT FROM AUTHOR]

A highly efficient enantioselective dicarbofunctionalization reaction of (E)-alkenyloxindoles with pyridinium salts was realized. The process includes the chiral N,N′-dioxide–Sc(III) complex-catalyzed regio-, diastereo-, and enantioselective [3+2] cycloaddition reaction and the following photo-promoted aza-Norrish II type rearrangement. A series of 2-pyridyl substituted oxindole derivatives were obtained in good yields with moderate to good diastereo- and enantioselectivities. [ABSTRACT FROM AUTHOR]

A highly enantioselective [2+2] cycloaddition reaction of alkylidene malonates with the internal C=C bond of N-allenamides was developed with a MgII/N,N′-dioxide complex as a catalyst. Various polysubstituted methylenecyclobutanes were afforded in good yields (up to 99%) and excellent enantioselectivities (up to 96% ee) under mild conditions. The utility of the donor–acceptor cyclobutane product was demonstrated as a masked 1,4-dipole in the formal [4+2] annulation reaction with a silyl enol ether. [ABSTRACT FROM AUTHOR]

Here we report an efficient asymmetric [4+2] cycloaddition of β,γ-unsaturated α-ketoesters with cyclobutenones. The corresponding products were obtained in good yields (up to 92%) with excellent enantioselectivities (up to 98% ee) and diastereoselectivities (up to ＞19/1 dr). Moreover, based on the control experiments and previous reports, a possible catalytic cycle was proposed. [ABSTRACT FROM AUTHOR]

A chiral N,N′-dioxide/Co(BF4)2·6H2O complex catalytic system has been developed to efficiently catalyze the asymmetric 1,3-dipolar cycloaddition of nitrones with methyleneindolinones. The corresponding chiral multisubstituted spiroisoxazolidines with three contiguous quaternary–tertiary stereocenters were obtained in moderate to high yields with excellent dr and ee values (up to 97% yield, ＞19 : 1 dr and 98% ee). [ABSTRACT FROM AUTHOR]

The catalytic enantioselective [2+2] cycloaddition between quinones and fulvenes was achieved, for the first time, by the use of a chiral copper(ii) complex catalyst. The transformation afforded a series of enantiomerically enriched [6,4,5]-tricyclic cyclobutane derivatives in good yields with excellent regio- and stereoselectivities. Furthermore, the [2+2] adducts could be easily converted into formal [3+2] adducts efficiently and stereoselectively. [ABSTRACT FROM AUTHOR]

A highly efficient catalytic asymmetric [4+2] cycloaddition of silyloxyvinylindoles with β,γ-unsaturated α-ketoesters has been accomplished by an available chiral N,N′-dioxide/yttrium triflate complex. A widespread range of carbazole derivatives were obtained in 47–98% yield with 86–99% ee under mild reaction conditions. [ABSTRACT FROM AUTHOR]

A highly efficient catalytic asymmetric formal [3+2] cycloaddition reaction of 5-alkoxyoxazoles with azodicarboxylate compounds has been realized by a chiral N,N′-dioxide/Co(BF4)2·6H2O complex. A series of poly-substituted 1,2,4-triazolines compounds were obtained in moderate to excellent yields (70–99%) with excellent enantioselectivities (82–98% ee). [ABSTRACT FROM AUTHOR]

An asymmetric inverse-electron-demand hetero-Diels–Alder reaction between o-quinone methides and azlactones to generate potentially pharmacological active dihydrocoumarins has been achieved efficiently by using a chiral N,N′-dioxide–Sc(iii) complex as the catalyst. The desired products were obtained in high yields with excellent enantioselectivities and diastereoselectivities (up to 94% yield, 96% ee and ＞19 : 1 dr) under mild reaction conditions. A concerted reaction pathway was confirmed by Operando IR and control experiments. [ABSTRACT FROM AUTHOR]

Enantioselective cyclization of α-isocyano esters with azodicarboxylates catalyzed by FeII–N,N′-dioxide complexes has been developed. Under mild conditions, a variety of 1,2,4-triazoline derivatives was obtained in high yields and enantioselectivities. [ABSTRACT FROM AUTHOR]