title: An efficient three-step synthesis of cyclopenta[b]pyrans via 2-donor-substituted fischer ethenylcarbenechromium complexes.
abstract: A wide range of cyclopenta[b]pyrans 4 has been synthesized in a one-pot reaction by treatment of different 2-donorsubstituted ethenylcarbenechromium complexes 2 with alkynes in THF in moderate to excellent yields (41-90 % for 14 out of 25 examples). The starting materials 2 are readily available in good to excellent yields (76-99 % for 25 out of 36 examples) by Michael addition of amines, alcohols and thiols, respectively, to the corresponding alkynylcarbenechromium complexes 1. Due to their 10 pi-electrons in a cross-conjugated bicyclic system, cyclopenta[b]pyrans have been termed pseudoazulenes, as they indeed have similar UV/Vis-spectroscopic properties.
authors.affiliation: Institut für Organische und Biomolekulare Chemie der Georg-August-Universität Göttingen, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: de Meijere
authors.forename: Heiko
authors.initials: H
authors.lastname: Schirmer
authors.forename: Frank
authors.initials: F
authors.lastname: Stein
authors.forename: Frank
authors.initials: F
authors.lastname: Funke
authors.forename: Michael
authors.initials: M
authors.lastname: Duetsch
authors.forename: Yao-Ting
authors.initials: YT
authors.lastname: Wu
authors.forename: Mathias
authors.initials: M
authors.lastname: Noltemeyer
authors.forename: Thomas
authors.initials: T
authors.lastname: Belgardt
authors.forename: Burkhard
authors.initials: B
authors.lastname: Knieriem