Ueber einige Hexaderivate des Benzols

Rhodizonate and croconate dianions as divergent hydrogen-bond acceptors in the self-assembly of supramolecular structures

“…Recently we initiated a program to explore the use of the nonbenzenoid aromatic oxocarbons C n O n 22 (n = 3, deltate; n = 4, squarate; n = 5, croconate; n = 6, rhodizonate), 1 each bearing a planar set of divergent hydrogen-bond acceptor sites, in combination with urea or thiourea, for the construction of anionic host frameworks that accommodate quaternary ammonium cations. In the series of inclusion complexes [Et 6 direct linkages between squarate and urea/thiourea exhibit the hydrogen bonding patterns I-IV shown in Fig. 1, which are further connected with the commonly occurring infinite urea/thiourea chains or ribbons 5 to generate two-or three-dimensional host networks.…”

“…We therefore decided to replace urea with phenylurea, whose bulky and hydrophobic substituent is expected to prevent, or at least suppress, the formation of urea ribbons. Furthermore, the rhodizonate dianion readily undergoes oxidative ring contraction through an a-oxo alcohol rearrangement, 6 which is related to the well known benzil-benzylic acid rearrangement, 7 to produce the croconate ion. Accordingly we developed a simple method to generate the rhodizonate ion in situ and incorporate it and its ringcontracted croconate product into the host lattices of new inclusion compounds [Bu 9)] 8 to form a pseudocentrosymmetric, slightly twisted X-shaped pentamer (Fig.…”

Benzoquinonediimine ligands: Synthesis, coordination chemistry and properties

“…However, the prompt aerial oxidation to DABQDI does not facilitate its usage but reveals instead to be a convenient method to access quinoidal systems. Historically, Nietzki brought to light the spontaneous oxidation of TAB under aerobic conditions in 1887 [75,76]. Nakata et al…”

Characterization of the Elusive Rhodizonate Ring‐Contraction Decarbonylation C5O4(OH)CO2Me2− Intermediate to Croconate

“…The oxidative ring contraction to croconate, C 5 O 5 2À , from rhodizonate in basic solution has previously been observed as long ago as 1837 (Scheme 1). [7,10] However, the postulated mechanistic C 5 O 4 (OH)CO 2 R 2À (R = H, Me) intermediate was never pre-viously observed. [7,10] This intermediate has been isolated as bridging between the pair of Co II sites in 2 2+ .…”

“…[7,10] However, the postulated mechanistic C 5 O 4 (OH)CO 2 R 2À (R = H, Me) intermediate was never pre-viously observed. [7,10] This intermediate has been isolated as bridging between the pair of Co II sites in 2 2+ .…”