γ-Substituted Allenic Amides in the Phosphine-Catalyzed Enantioselective Higher Order Cycloaddition with Azaheptafulvenes
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Date
2020-05-28Author
Romaniega, Aketza
Díaz, Estibaliz
Reyes Martín, Efraim
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Organic Letters 22(12) : 4721−4725(2020)
Abstract
Racemic γ-substituted allenes undergo enantioselective higher order [8 + 2]-cycloaddition with azaheptafulvenes using a chiral amino acid derived amidophosphine as catalyst, providing the corresponding azaazulenoid cycloadducts with excellent levels of regio-, diastereo-, and enantioselectivities. In this reaction, the activated allylic phosphonium ylide intermediate participates as the C2-component of the reaction, in contrast to the conventional reactivity of this type of zwitterionic intermediates as C3-components in cycloaddition reactions.