Asymmetric catalytic [4+3] cycloaddition of ortho-quinone methides with oxiranes.

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.

Lewis acid catalysed asymmetric cascade reaction of cyclopropyl ketones: concise synthesis of pyrrolobenzothiazoles.

Utilizing the C4 reactive site of cyclopropyl ketones and a chiral N,N'-dioxide-scandium(iii) complex as a catalyst, a concise ring-opening/cyclization/thio-Michael cascade method was developed for the synthesis of chiral benzothiazole derivatives from a simple 2-aminothiophenol material. The kinetic resolution and the origin of stereoselectivity were elucidated via a possible catalytic model.

Lewis acid catalyzed asymmetric [4+2] cycloaddition of cyclobutenones to synthesize α,ß-unsaturated δ-lactones.

Here we report an efficient asymmetric [4+2] cycloaddition of ß,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.

Asymmetric Ring Opening/Cyclization/Retro-Mannich Reaction of Cyclopropyl Ketones with Aryl 1,2-Diamines for the Synthesis of Benzimidazole Derivatives.

A highly efficient asymmetric ring-opening/cyclization/retro-Mannich reaction of cyclopropyl ketones with aryl 1,2-diamines has been realized using a chiral N,N'-dioxide/Sc(III) catalyst. Benzimidazoles containing chiral side chains were generated under mild reaction conditions in excellent outcomes (up to 99 % yield and 97 % ee). This method also provides efficient access to chiral benzimidazole-substituted amide and cycloheptene derivatives.

Asymmetric Ring-Opening of Cyclopropyl Ketones with Thiol, Alcohol, and Carboxylic Acid Nucleophiles Catalyzed by a Chiral N,N'-Dioxide-Scandium(III) Complex.

A highly efficient asymmetric ring-opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N'-dioxide-scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99% yield and 95% ee. This is also the first example of one catalytic system working for the ring-opening reaction of donor-acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version.