Palladium‐Catalyzed (5+3) Annulation of 4‐Vinyl‐4‐Butyrolactones with C,N‐Cyclic Azomethine Imines: Construction of Eight‐Membered Ring

Abstract

In this paper, we designed and synthesized 4-vinyl-4-butyrolactone as a precursor to generate the zwitterionic allylpalladium intermediates, which behaved as five-membered all-carbon synthon in palladium-catalyzed (5 + 3) annulation with azomethine imines, giving eight-membered ring-fused heterocycles (26 examples, 49% to 97% yield, > 20:1 dr).

Fungicide-inspired precursors of π-allylpalladium intermediates for palladium-catalyzed decarboxylative cycloadditions

“…A variety of precursors with diverse structures have been invented to realize numerous useful cycloaddition reactions. On the basis of their structures, these precursors can be categorized as vinyl cyclic carbonates, 2 methylidene cyclic carbonates, 3 vinyl cyclic carbamates, 4 methylidene cyclic carbamates, 5 vinyl lactones, 6 methylidene lactones 7 and acyclic carbonates. 8 Among them, cyclic carbamates 4−5 and lactones 6,7 were usually used for synthesis of functionalized nitrogen heterocycles and carbocycles.…”

“…On the basis of their structures, these precursors can be categorized as vinyl cyclic carbonates, 2 methylidene cyclic carbonates, 3 vinyl cyclic carbamates, 4 methylidene cyclic carbamates, 5 vinyl lactones, 6 methylidene lactones 7 and acyclic carbonates. 8 Among them, cyclic carbamates 4−5 and lactones 6,7 were usually used for synthesis of functionalized nitrogen heterocycles and carbocycles. In the structures of these typical precursors, an electron-withdrawing group was often needed and linked with an atom at the α-position of the carbonyl in the ring (Scheme 1a).…”

Synthesis of biologically active [1,5]diazocino[2,1-b]quinazolinones through [4 + 4] cycloaddition of 2-alkynyl quinazolinones with aza-ortho-quinone methides

“…2 As some of the most important aza-eight-membered ring compounds, the significance of these privileged diazocine skeletons has led to a great demand for efficient synthetic methods. 3 Many elegant strategies have been developed for the preparation of aza-eight-membered ring compounds, such as intramolecular cyclization, 4 coupling reaction, 5 [5 + 3], 6 [6 + 2] 7 or [4 + 4]/[4 + 2 + 2] cycloaddition, 8 or other cascade reactions. 9 However, many reported methods cannot be used to prepare [1,5]diazocines.…”

Studies on the [4 + 2] cycloaddition and allylic substitution of indole-fused zwitterionic π-allylpalladium

“…Therefore, designing and synthesizing precursor compounds are vital parts of researching zwitterionic π-allylpalladium species. To date, many precursor compounds, including vinyl cyclic carbonates, 3 vinyl lactones, 4 vinyl oxirane, 5 and vinyl oxetane, 6 have been developed (Fig. 1a).…”