Pentacarboxycyclopentadienes in Organic Synthesis

Abstract

The review summarizes the literature data on the synthesis, structure, reactivity, and rearrangements of pentacarboxycyclopentadienes and their derivatives. Their potential for creating new chiral organic catalysts for enantioselective Diels-Alder reactions, cationic polymerization of vinyl ethers, enantioselective protonation of silylenol ethers, aminomethylation, and other processes is described, and aspects of their use as effective carriers of functional groups, new ligand systems for the synthesis of metal complexes and donor-π-acceptor chromophores for organic photovoltaics are considered.

Aza-Achmatowicz rearrangement coupled with intermolecular aza-Friedel–Crafts enables total syntheses of uleine and aspidosperma alkaloids

“…Notably, the C2-C2 0 coupling product was not observed. It was noteworthy that the widely used Lewis acid BF 3 -Et 2 O gave a lower yield of 3a (60%, entry 8) while the unusual organic Brønsted acid pentacarbomethoxycyclopentadiene (PCCP) [89][90][91] in toluene delivered slightly higher yield (90%, entry 9). Surprisingly, the iAFC reaction of indole 1b with AAR product 2a under various acidic conditions gave consistently lower yields of 3b (0-58%, entries 10-18), which might be due to the steric hindrance exerted by the C2-alkyl substituent.…”