Generation of Cyclopentadiene for Diels–Alder Reactions by Visible‐Light Irradiation of Iron Sandwich Complexes

Abstract

Cyclopentadienes readily undergo fast and selective Diels-Alder reactions which can be used for conjugation of biomolecules and polymers. Herein we present a new method for the photochemical generation of cyclopentadienes by the visible light irradiation of the iron complexes [(C 5 H 4 R)Fe(arene)] + . This reaction proceeds at room temperature, in water, and in the presence of potentially interfering amino acids. Free cyclopentadiene is trapped by dienophiles to give the corresponding Diels-Alder adducts in 72-95 % yield.

Aromaticity enhancement of cyclopentadiene in piperidine derivatives: a DFT study on combination of the anomeric effect and Schleyer hyperconjugative aromaticity

“…[9][10][11] Cyclopentadiene (herein after referred to as ''Cp'') is one of the most important reactive dienes in the Diels-Alder reaction. [12][13][14][15] Recently, Cp reactions in click chemistry have been reviewed by Levandowski and Raines. 16 About 80 years ago, Mulliken reported that Cp has longer ultraviolet absorption wavelengths in comparison to open-chain dienes.…”

Photochemically induced formation of adhesive hydrogels from sodium alginate, acrylamide, and iron sandwich complexes

“…10 Because of this, [(C 5 H 5 )Fe(arene)] + complexes have been used as photoinitiators for the cationic polymerization of epoxides and other monomers. 11–14 In addition, we have recently reported the application of such complexes for the controlled photochemical release of cyclopentadienes, 15 as well as for the photochemical patterning by salicylate dyes, that coordinate with iron ions. 16,17 However, these complexes have not been used for photochemical gelation before this work.…”