Abstract
Asymmetric cyclization of alkenoic acids was realized by the use of an iridium/chiral bisphosphine catalyst, giving high yields of the corresponding γ-lactones with good enantioselectivity.
Highlights
Asymmetric cyclization of alkenoic acids was realized by the use of an iridium/chiral bisphosphine catalyst, giving high yields of the corresponding c-lactones with good enantioselectivity
Transition metal-catalyzed addition of carboxylic acids was pioneered by Shvo and Rotem, who reported the Ru-catalyzed addition of carboxylic acids to alkynes,2a,b and there have been many successful examples of the addition to alkynes[2] and allenes.[3,4]
An inherent problem in the asymmetric addition of carboxylic acids to alkenes is a non-asymmetric background reaction catalyzed by a strong Brønsted acid, which has been reported to be sometimes formed by use of metal triflates or cationic metal catalysts.[15]
Summary
Asymmetric cyclization of alkenoic acids was realized by the use of an iridium/chiral bisphosphine catalyst, giving high yields of the corresponding c-lactones with good enantioselectivity. A Reaction conditions: carboxylic acid 1 (0.20 mmol), [IrCl(coe)2]2 (5 mol% Ir) and (R)-DTBM-segphos in NMP (0.80 mL) at 100 1C for 20 h.
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