Brom-cyclobutadien-eisentricarbonyl / Bromo-cyclobutadiene-irontricarbonyl

Abstract

The synthesis of bromo-cyclobutadiene-irontricarbonyl is reported and compared with a former attempt of synthesis that yielded another product. Spectra are discussed with respect to structure and bonding properties. Im Rahmen von Untersuchungen über

(Cyclobutadiene)iron TricarbonylA Case of Theory before Experiment

“…Instead of the expected product, bis[(cyclobutadiene)iron tricarbonyl] ( 25 ) was obtained . However, the reaction of 1,3,4-tribromocyclobutene with Fe 2 (CO) 9 was successful, giving (bromocyclobutadiene)iron tricarbonyl …”

“…56 However, the reaction of 1,3,4-tribromocyclobutene with Fe 2 (CO) 9 was successful, giving (bromocyclobutadiene)iron tricarbonyl. 57 An alternate one-pot synthesis of (cyclobutadiene)iron tricarbonyl, the reaction of photo-R-pyrone with iron pentacarbonyl (eq 5), was reported by Michael Rosenblum (who in Woodward's laboratory explored the organic chemistry of ferrocene in 1952 and found it to be a highly reactive aromatic system) and Gatsonis. 58 The yield of (cyclobutadiene)iron tricarbonyl, however, was not high and (R-pyrone)iron tricarbonyl (26) also was formed in the reaction.…”

A Metal-Free Cyclobutadiene Reagent for Intermolecular [4 + 2] Cycloadditions

“…We then turned our attention to preparing a substituted cyclobutadiene. After consulting the literature, we noted that the synthesis of bromocyclo­butadiene was underexplored, yet we anticipated rapid access from 8a . Therefore, 8a was dibrominated to yield 23 as an inconsequential mixture of isomers, which was eliminated with DBU to yield 24 in 48% yield over this sequence (Scheme B).…”