Palladium‐Catalyzed [6+2] Double Allene Annulation for Benzazocines Synthesis

Abstract

An efficient double allene protocol for the formation of benzazocines has been developed. The reaction constitutes a highly regioselective palladium‐catalyzed formal [6+2] annulation of allenyl benzoxazinanones with terminal allenes forming the challenging 8‐membered cycles. Decent yields and excellent regioselectivity have been observed under mild conditions with a remarkable Z‐stereoselectivity for the exo‐cyclic C=C bonds. The synthetic potentials of benzazocine products have been demonstrated.

Recent progress in the construction of eight-membered nitrogen-heterocycles

“…A plausible mechanism was proposed for the Au-catalyzed In 2022, Ma and co-workers developed the Pd-catalyzed [6+2] cycloaddition reaction of allenyl benzoxazinanone 72 with allenes 73 to synthesize benzazocines 74 (Scheme 14A). 46 In this process, the methylene-p-allylic metal intermediate was formed by the coordination of the Pd catalyst with 72 bearing a leaving group at the a-position. Notably, the N-protecting group in allenyl benzoxazinanone has an obvious impact on the cycloaddition reaction.…”

Advancements in Asymmetric Catalytic Approaches Involving Benzoxazinone Derivatives

“…Based on the features of allenyl extensively utilized in Pd‐catalytic reactions, Ma's group first introduce an allene unit to the benzoxazinones to design a novel reactive substrates and demonstrated a highly regioselective palladium catalyzed formal [6+2] annulation of allenyl benzoxazinones 4 with terminal allenes forming the challenging eight‐membered cycles [72] . Almost simultaneously, Wang, Yuan and co‐workers developed a Pd‐catalyzed asymmetric cascade intramolecular cyclization/intermolecular Michael addition reaction between 1‐azadienes 108 and allenyl benzoxazinones 4 generated form η 2 ‐Pd(0) complex as Michael donor, accessing to a range of chiral C2‐functionalized quinoline derivatives 109 in good yields (up to 93%) with high enantioselectivities (up to 93% ee) (Scheme 44).…”

Effect of particle dispersion on electrochemical performance of Prussian blue analogues electrode materials for sodium ion batteries

“…), □ represents [Fe(CN) 6 ] vacancy, and n represents the percentage of crystalline water present in the crystal structure [17–19] . PBAs have high theoretical capacity (~170 mAh g −1 ) and output voltage (~3.5 V), as well as advantages such as easy synthesis and environmental protection, which have attracted more interest and attention from researchers [20–24] . At present, co‐precipitation method has become the main approach for synthesizing PBAs due to its advantages of simple operation, short time, and low cost [25–27] .…”