De Novo Construction of Substituted Terephthalates via Phosphine Catalyzed Domino Benzannulation Reactions

Abstract

The robustness of phosphine catalysis enabling the domino benzannulation reactions of allenoates with enamines is described. A broad array of substituted terephthalates were delivered under simple and practical reaction conditions. Furthermore, the reaction could be carried out on a gram scale with higher yield, and various conversions of the terephthalate products demonstrate the versatility of this transformation.

Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction

“…A triphenylphosphine-catalysed domino [4 + 2] benzannulation of enamino esters 108 and β'-acetoxyallenoates109 to afford substituted terephthalates 110 has been developed by Huang and colleagues (Scheme 34). [45] It is noteworthy that an enamine derivative with an electron withdrawing substituent on aryl ring (R 1 ) furnished the terephthalate product in excellent yield, whereas the one with a methoxy substituent on the aryl ring did not afford any benzannulated product at all.…”

Tertiary‐Amine Controlled (3+3) or (4+2) Annulations of β′‐Acetoxy Allenoates with N‐Sulfonyl Ketimines: An Entry to m‐Teraryl and Fused Dihydropyridines

“…The electronic factors involving phosphines are quite different from those of tertiary amines, and hence annulation/cyclization mediated by these could lead to different products. The reactions shown in Scheme 1a–c were driven toward the ring construction by the initial attack of nucleophiles at the γ ‐carbon in diene‐ammonium [6f] or diene‐phosphonium [7i–j] intermediate. It is also important to note that even alicyclic tertiary amines (e. g., DABCO) and aromatic amines (e. g., DMAP) show markedly distinct pathways in reactions involving allenoates as shown earlier by Huang and coworkers in the reaction of allenoates with sulfonyl‐substituted α,β‐unsaturated ketimines (Scheme 1d) [8] …”