Vinylcyclopropanes as All-Carbon 1,5-Dipoles: A Reactivity Switch for Palladium-Catalyzed (5 + 4) Cycloadditions

Abstract

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High-order dipolar annulations with metal-containing reactive dipoles

“…63 In 2021, Archambeau and coworkers disclosed a Pdcatalyzed (5+4) annulation between VCP 103 and azadienes 82, which furnished 9-membered N-heterocycles 108 in good yields (Scheme 23). 64 In 2018, by combining Pd and NHC catalysts, Glorius and coworkers realized (5+2) annulations of VECs 96 with enals 109. 65 As illustrated in Scheme 24, a,b-unsaturated aldehyde 109 is converted to Breslow intermediate 111 with an NHC catalyst that attacks the terminal carbon of the in situ generated 1,5-dipole, affording 101.…”

“…63 In 2021, Archambeau and coworkers disclosed a Pd-catalyzed (5+4) annulation between VCP 103 and azadienes 82 , which furnished 9-membered N-heterocycles 108 in good yields (Scheme 23). 64…”

Pd-catalyzed exclusively regioselective [5 + 4] cycloaddition for the construction of 1,5-di/ox-azonanes

“…4 [5 + 4] cycloaddition, as an efficient and flexible approach, provides a significant advantage of directly coupling two building blocks (serving as dipoles and dipolarophiles) to produce nine-membered heterocycles. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In 2017, the Zhao group 5,6 reported the first [5 + 4] cycloaddition between α,β-unsaturated imines and vinylethylene carbonates (VECs) for the construction of nine-membered heterocycles via palladium catalysis. Since then, a series of excellent studies about palladium-catalyzed [5 + 4] cycloaddition involving 1,5dipoles and α,β-unsaturated imines have been reported by Zhao, 8,14 Archambeau, 15 Guo, 16 Hu 17,18 and Li 21 groups.…”

A Lewis Acid-Promoted Michael Addition and Ring-Expansion Cascade for the Construction of Nitrogen-Containing Medium-Sized Rings

“…Particularly, azadienes, which act as special α,β -unsaturated imines, have been successfully used as effective four-atom synthons to produce nitrogen-containing medium-sized rings through a formal high-order [4 + n] annulation process [ 36 , 37 , 38 , 39 ]. For example, the palladium-catalyzed [4 + 4] [ 40 , 41 ], [5 + 4] [ 42 , 43 , 44 , 45 , 46 ] or [6 + 4] [ 47 ] annulation established by Zhao, Yao, Lin and co-workers using pyrrole-, benzofuran- or indole-fused azadienes as substrates have proven to be efficient in assembling these frameworks. In 2017, Lu and colleagues disclosed an elegant phosphine-catalyzed enantioselective formal [4 + 4] annulation of azadienes for the synthesis of azocanes [ 48 ].…”