Pd-Catalyzed Intramolecular Dearomative [4 + 2] Cycloaddition of Naphthalenes with Arylalkynes

Abstract

A Pd-catalyzed intramolecular dearomative [4 + 2] cycloaddition reaction of naphthalenes with arylalkynes is developed. The protocol provides a straightforward method to access a range of polycyclic dihydronaphthalenes containing two vicinal all-carbon stereocenters in moderate yields under mild conditions in an air atmosphere. The deuterium labeling experiment suggests a pathway involving electrophilic dearomatization followed by Friedel−Crafts cyclization. Several synthetic transformations of the product were conducted to demonstrate the utility of this reaction.

Transition‐Metal Catalyzed [4+2]‐Cycloaddition Reactions: A Sexennial Update

“…Lu et al in 2023 reported an intramolecular palladiumcatalyzed dearomative [4 + 2] cycloaddition reaction of naphthalenes with arylalkenes of 98 to afford polycyclic dihydronapthalenes containing two vicinal all-carbon stereocenters 99 in moderate yields under mild conditions in an air atmosphere (Scheme 26). [106] Initially, Pd(II) coordinates with alkyne generated carbocation Int-LVI by trans-electrophilic dearomatization. LVI underwent Friedel-Crafts cyclization to give LVII, which subsequently underwent deprotonation to provide LVIII.…”

“…Palladium catalyzed synthesis of polycyclic dihydronapthalenes. [106] electron-poor α,β-unsaturated 3-vinyl indoles 117 using Cu(II) as the catalyst in good to excellent yields and diastereoselectivities (Scheme 32). [128] The mechanism involved activation of 117 by Cu(OTf) 2 to give 1,5-dipolar Int-LXXX.…”