Synthesis and Catalytic Activity of Bifunctional Phase-Transfer Organocatalysts Based on Camphor

Ten novel bifunctional quaternary ammonium salt phase-transfer organocatalysts were synthesized in four steps from (+)-camphor-derived 1,3-diamines. These quaternary ammonium salts contained either (thio)urea or squaramide hydrogen bond donor groups in combination with either trifluoroacetate or iodide as the counteranion. Their organocatalytic activity was evaluated in electrophilic heterofunctionalizations of beta-keto esters and in the Michael addition of a glycine Schiff base with methyl acrylate. alpha-Fluorination and chlorination of beta-keto esters proceeded with full conversion and low enantioselectivities (up to 29% ee). Similarly, the Michael addition of a glycine Schiff base with methyl acrylate proceeded with full conversion and up to 11% ee. The new catalysts have been fully characterized; the stereochemistry at the C-2 chiral center was unambiguously determined.

Automated summary

Ten novel bifunctional quaternary ammonium salt phase-transfer organocatalysts were synthesized and evaluated for their organocatalytic activity in electrophilic heterofunctionalizations and the Michael addition reaction. The reactions showed high conversion rates, but low enantioselectivities. The catalysts were fully characterized and the stereochemistry at the C-2 chiral center was determined.