Scheme 7. Chiral Ni-Catalyzed 1,3-DC of Nitrones Scheme 8. Use of α′-Hydroxy Enones as Dipolarophile Scheme 9. Use of 2-Alkenoyl Imidazoles Scheme 10. Use of α′-Phosphoric Enones Scheme 11. Use of Alkenoyl Pyridine N-Oxides

No abstract

An axially chiral dicarboxylic acid has been prepared as a new class of chiral hydrogen-bonding catalysts and applied to the highly enantioselective Mannich reaction of arylaldehyde N-Boc imines and diazo compounds.

A diverse array of chiral organocatalysts have been developed that rely on acid-base interactions to promote enantioselective ionic reactions via the movement of electron pairs. The stereocontrol of radical reactions using organocatalysts is an alternative approach, and several studies have shown that synthetically useful reactivity can result by controlling the movement of single electrons. However, in these studies, it is still an acid-based organocatalyst which forms a closed-shell intermediate with substrate prior to the radical reaction and imparts chiral information, and use of a chiral organic radical directly as catalyst has only rarely been explored. Here, we report the design of an organic thiyl radical catalyst with a carefully designed chiral pocket constructed around a chiral thiol precatalyst. The resulting catalyst was used to effect highly diastereo- and enantioselective C-C bond-forming radical cyclizations.

Allenes are molecules based on three carbons connected by two cumulated carbon-carbon double bonds. Given their axially chiral nature and unique reactivity, substituted allenes have a variety of applications in organic chemistry as key synthetic intermediates and directly as part of biologically active compounds. Although the demands for these motivated many endeavours to make axially chiral, substituted allenes by exercising asymmetric catalysis, the catalytic asymmetric synthesis of fully substituted ones (tetrasubstituted allenes) remained largely an unsolved issue. The fundamental obstacle to solving this conundrum is the lack of a simple synthetic transformation that provides tetrasubstituted allenes in the action of catalysis. We report herein a strategy to overcome this issue by the use of a phase-transfer-catalysed asymmetric functionalization of 1-alkylallene-1,3-dicarboxylates with N-arylsulfonyl imines and benzylic and allylic bromides.