Rapid Construction of Polycyclic Ketones and the Divergent Kinetic Resolution Using Ruthenium‐Catalyzed Transfer Hydrogenation

Abstract

A unique cascade sequence of vinylogous Michael addition‐Michael addition‐oxa‐Michael addition using dienone substrates was reported for the first time, achieving the rapid construction of 5/6/5 fused ring compounds in good yields with good to high stereoselectivities under mild conditions. Enantioenriched polycyclic rings can be obtained with high level of enantioselectivity by the stereodivergent resolution using ruthenium‐catalyzed transfer hydrogenation. The protocol provides a concise approach for the construction of the related fused ring substances.

Asymmetric transfer hydrogenation of boronic acid pinacol ester (Bpin)-containing acetophenones

“…1), 1 has been successfully applied extensively to a wide range of ketone substrates. Excellent results have been obtained for the ATH of acetophenone derivatives, 2 acetylenic ketones, 3 fluorinated derivatives, 4 as well as dynamic kinetic resolutions of a number of substrate classes. 5 Functional groups which are known to be compatible with Noyori–Ikariya catalysts include oxygenated, nitrogen-containing, carboxy groups, and halides.…”

“…5 Functional groups which are known to be compatible with Noyori–Ikariya catalysts include oxygenated, nitrogen-containing, carboxy groups, and halides. 1–5…”

Asymmetric Total Synthesis of Twin Bufogargarizins A and B

“…In addition, to our knowledge, there are few methods reported concerning the preparation of such a [7−5−6−5] tetracyclic skeleton. 8 In 2018, we developed an approach to construct the core of bufogargarizin A; 9 however, after extensive trials, its total synthesis with this approach has been proven to be very difficult. In our long-standing efforts in the synthesis of bioactive abeo-steroids, 10 we herein wish to describe the first and asymmetric total synthesis of bufogargarizins A and B, using the intramolecular Ru-catalyzed [5 + 2] cycloaddition reaction of a vinyl ether cyclopropane-yne.…”