イリド形成反応を基盤とする触媒的不斉1,3-双極性付加環化反応

抄録

Enantioselective 1,3-dipolar cycloaddition reactions of cyclic carbonyl ylides have received a great deal of attention due to their synthetic utilities for asymmetric syntheses of medium-sized polycyclic ethers containing epoxy-bridged moieties such as 8-oxabicyclo[3.2.1]octane derivatives, which are recognized as common structural units in naturally occurring biologically important compounds. Rh(II)-catalyzed intramolecular carbenoid-carbonyl cyclization reactions of diazo carbonyl compounds are one of the most efficient methodologies for generation of cyclic carbonyl ylides. Although some catalytic asymmetric methods using chiral Rh catalysts have been developed, related works on other asymmetric catalysts including a dual catalytic system have rarely been demonstrated. We have developed a new catalytic system, an achiral Rh complex/chiral Lewis acid system, for the asymmetric 1,3-dipolar cycloaddition reactions of cyclic carbonyl ylides with benzyloxyacetaldehyde derivatives, α-keto esters, and 3-alkenoyl-2-oxazolidinones. Our methodology can be applied not only to normal electron-demand cycloadditions but also to inverse electron-demand cycloadditions using electron-rich dipolarophiles such as vinyl ethers and N-methylindoles. This article describes the range of the diazocarbonyl compounds as the cyclic carbonyl ylide precursors and their synthetic applications to chiral indolizidine alkaloids, including (+)-Tashiromine. Asymmetric 1,3-dipolar cycloadditions between diazo imine-derived cyclic azomethine ylides and a 2-acryloyl-3-pyrazolidinone using the dual catalytic system, which afford optically active 8-azabicyclo[3.2.1]octane derivatives, are also reported.