Abstract
The Rauhut–Currier (RC) reaction represents an efficient method for the construction of carbon–carbon bond in organic synthesis. However, the RC reactions involving allenoate substrates are very rare, and in particular, asymmetric intramolecular RC reaction of allenoates is yet to be discovered. Here, we show that the intramolecular RC reaction proceeds smoothly in the presence of 1 mol% β-ICD, and bicyclic lactones are obtained in high yields and with excellent enantiomeric excesses. With the employment of γ-substituted allenoates as racemic precursors, a novel dynamic kinetic resolution of allenes via RC reaction is observed, which allows for facile synthesis of highly enantiomerically enriched allenes.
Highlights
The Rauhut–Currier (RC) reaction represents an efficient method for the construction of carbon–carbon bond in organic synthesis
It should be noted that the Lewis base-triggered nucleophilic zwitterion may react differently (Fig. 1, pathway b): addition of activated nucleophilic species to activated olefin without subsequent cyclization would lead to an allenoate Rauhut–Currier (RC) process
Chiral amine catalyst b-ICD was chosen for the enantioselective version of the reaction
Summary
The Rauhut–Currier (RC) reaction represents an efficient method for the construction of carbon–carbon bond in organic synthesis. When a prochiral cyclohexadienone with an allene moiety is subjected to Lewis base activation, and the zwitterionic intermediate generated may undergo different reactions; the Lu’s [3 þ 2] cyclization may create a tricyclic system, and the RC-type reaction will give a bicyclic lactone with an exo-cyclic allene structure. While both pathways are feasible, we envisioned judicious selection of catalytic systems will make unprecedented RC reaction of allenoates favourable. By employing substrates with g-substituted allene moieties, we develop a dynamic kinetic resolution (DKR) process to access chiral allenes
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