Direct Synthesis of Polycyclic Tropinones by a Condensation-[4+3]-Cycloaddition Cascade Reaction

Tsubasa Okamoto; Miki Shibata; Sangita Karanjit; Atsushi Nakayama; Masahiro Yoshida; Kosuke Namba

doi:10.1002/chem.201802011

Direct Synthesis of Polycyclic Tropinones by a Condensation-[4+3]-Cycloaddition Cascade Reaction

Chemistry. 2018 Jul 5;24(38):9508-9513. doi: 10.1002/chem.201802011. Epub 2018 Jun 10.

Authors

Tsubasa Okamoto¹, Miki Shibata¹, Sangita Karanjit¹, Atsushi Nakayama¹, Masahiro Yoshida², Kosuke Namba¹

Affiliations

¹ Department of Pharmaceutical Science, Tokushima University, 1-78-1 Shomachi, Tokushima, 770-8505, Japan.
² Department of Pharmaceutical Science, Tokushima bunri University, Tokushima, 770-8514, Japan.

PMID: 29701268
DOI: 10.1002/chem.201802011

Abstract

A concise method of constructing polycyclic tropinone frameworks was developed. The single-step synthesis of polycyclic tropinone consists of an intramolecular [4+3] cycloaddition reaction of N-nosyl-pyrrole with oxyallyl cation that was generated in situ by an intermolecular condensation reaction of the nucleophilic functional groups on a tethered pyrrole with the aldehyde of 2-(silyloxy)-acrolein. This cascade reaction afforded various polycyclic tropinones including tri-, tetra-, and pentacyclic systems in high yields as single diastereomers.

Keywords: cycloaddition; oxyallyl cation; pyrrole; synthetic methods; tropane alkaloid.