A palladium-catalyzed approach to allenic aromatic ethers and first total synthesis of terricollene A

Abstract

A palladium-catalyzed C-O bond formation reaction between phenols and allenylic carbonates to give 2,3-allenic aromatic ethers with decent to excellent yields under mild reaction conditions has been described. A variety...

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

“…On the other hand, allenes bearing a leaving group at α‐position could react with transition metal catalysts to generate the methylene‐π‐allylic metal intermediate, [5] which may readily undergo substitution reaction with stabilized nucleophiles or non‐stabilized nucleophiles to give either allenes [6, 7] and/or conjugated 1,3‐dienes, [8] respectively (Scheme 1b). With our longstanding interest in developing new catalytic reactions of 2,3‐allenyl derivatives, [6c–f, 7e–l, 8m] we envisaged that an insertion reaction of such methylene‐π‐allylic metal intermediates with an unsaturated C−C bond would generate intermediates Int‐A and/or Int‐B (Scheme 1c). Herein, we wish to demonstrate the first example of such a concept: the unexpected Pd‐catalyzed formal [6+2] annulation of allenyl benzoxazinanones with allenes providing benzazocine derivatives highly efficiently with an exclusively Z stereoselectivity for non‐terminal exo‐cyclic C=C bond via Int‐B (Scheme 1d) [9, 10] .…”