Rhodium‐Catalyzed Pauson–Khand‐Type Cyclization of 1,5‐Allene‐Alkynes: A Chirality Transfer Strategy for Optically Active Bicyclic Ketones

Abstract

An efficient chirality transfer in the [RhCl(CO) 2 ] 2catalyzed [2+ +2+ +1] cyclization of optically active axially chiral 1,3-disubstituted allenynes with CO to access optically active bicyclopentenone compoundsh as been developed. The distal C=Cb ondo fallenesr eactedw ith the alknye unit and CO to afford [4.3.0]-bicyclic products with high ee values under mild reaction conditions with an excellent selectivity. Scheme1.Some typicalb ioactiveand natural compounds containingac yclopentenone unit.Scheme2.Rhodium-catalyzed allenic Pauson-Khand reactions.

Engaging Yne‐Allenes in Cycloaddition Reactions: Recent Developments

“…used a chirality transfer strategy to synthesize optically active bicyclopentenones 67 in 64%—97% yields with 90%—96% ee values through a Rh‐catalyzed [2 + 2 + 1] cyclization of optically active axially chiral 1,3‐disubstituted yne‐allenes 66 with CO (Scheme 21). [ 78 ] Various chiral TsN‐, (CO 2 Me) 2 C‐ and O‐linked yne‐allenes 66 and internal alkyne possessing alkyl, aryl, silyl substituents are suitable for this reaction, affording the target [4.3.0]‐bicyclic products by utilizing [RhCl(CO) 2 ] 2 and AgSbF 6 as co‐catalyst.…”

Chirality Transfer Intramolecular Pauson–Khand Reaction with N–C Axially Chiral Sulfonamides Bearing an Ene–Yne Structure

“…Thus, it was predicted that an intramolecular Pauson–Khand reaction with enantioenriched sulfonamides 1 would be a chirality transfer reaction but not a diastereoselective reaction. Although a chirality transfer Pauson–Khand reaction with enantioenriched allene derivatives has previously been reported, as far as we know, a reaction with atropisomeric substrates remains unknown.…”

Rh(I)-Catalyzed Allenic Pauson–Khand Reaction to Access the Thapsigargin Core: Influence of Furan and Allenyl Chloroacetate Groups on Enantioselectivity

“…Tg’s bioactivity and molecularly complex 5,7,5-ring system have captured the interest of the synthetic community with three total syntheses and several synthetic approaches. − Tg analogues have been prepared to understand the pharmacophoric groups that are important for biological activity. , However, these analogues are mostly accessed semisynthetically, limiting both their structural diversity and structure–activity relationship studies. − Moreover, Tg’s interesting biological activity motivates a continuing search for analogues having potent activity that are less toxic. To this end, we have previously shown that racemic allene-yne 6 undergoes an allenic Pauson–Khand reaction (APKR) to give the enantioenriched 5,7-ring system ( R )- 7 via a stereoconvergent dynamic kinetic asymmetric transformation (DyKAT) process (Scheme b). ,− Herein, we report rapid access to the enantioenriched 5,7,5-ring system of Tg using this APKR strategy and describe our continuing investigations with the aim of understanding the influence of the allene-yne precursor on the yield and enantioselectivity of the stereoconvergent APKR, specifically, groups on the alkyne terminus, tether, and allene (Scheme c).…”