The synthesis of [15]annulenone 4,7:10,13-dioxides and aromatic 4,7:10,13-dioxido[15]annulenium cations

Construction of synthetic macrocyclic compounds possessing subheterocyclic rings, specifically pyridine, furan, and thiophene

“…Removal of the carboxylic acid groups was accomplished through initial saponification of 200c to the triacid, then decarboxylation by treatment with quinoline and copper chromite at 200-205 °C to afford the desired unsubstituted [18]annulene trioxide (200a). This general cyclocondensation procedure utilizing either the Perkin reaction (an aldehyde and substituted acetic acid)110,162 or aldol condensation142,164 has been applied to the construction of numerous related annulenes.142,160,162, 164 An alternate, shorter procedure, albeit more convenient sy- Elix has reported a synthesis of annulenes from sucrose148 via an appropriately substituted Wittig reagent prepared from 5-chloromethyl-2-furfural. 353 The slow addition of lithium ethoxide to this phosphonium salt in dimethylformamide resulted in an intermolecular cyclocondensation to give (0.07 %) trioxide 200a along with two isomeric [24]annulene tetraoxides, two isomeric [30]annulene pentoxides, and an [36]annulene hexoxide of unknown configuration.148 •155 With the availability of polyunsaturated bis-aldehydes, Saikachi et al prepared several novel carbon-nitrogen-bridged furan macrocycles.174 When di-frans-1,2-bis[/8-(5'-formyl-2'-sucrose ref 353 ,CHO CH2CI CH=P(Ph)3 furyl)vinyl] benzene was condensed with o-phenylenediamlne, the expected annelated diaza [20]annulene dioxide was not formed but rather 218c, 218b, and 218a were isolated in 15, 1, and 15.7%, respectively.…”

Aromaticity and Möbius Antiaromaticity in Monocyclic [11]Annulenium Cations

“…We also investigated the fusion of various numbers of three-membered rings (3MRs) to the central 11-membered ring (11MR). We found several planar, all-cis-[11]annulenium ion derivatives as well as another Mo ¨bius antiaromatic species (52b); for comparison, we also found planar, antiaromatic all-cis-[12]annulene (60) and [15]annulenium cation (61) derivatives. The (anti)aromatic characterization of these compounds is based mainly on calculated magnetic data for the ground singlet and vertical triplet states, although aromatic stabilization energies (ASE) are also considered.…”

“…Because tropylium ion (15) and 34 are planar with unusual angles and their optimized dihydroaromatics would not be, we chose to constrain all the dihydroaromatics to planarity; the consequent torsional interactions of the saturated C-H bonds would be expected to cancel. However, there remains the problem that the charge delocalization in the aromatic ion is different from that in the dihydroaromatic ion, and the apparent ASE has to be reduced by an amount corresponding to the diminished charge delocalization in the dihydroaromatic (which makes its energy too high).…”

“…Diamagnetic susceptibilities, in centimetergram-second parts per million (χ), were calculated using the continuous set of gauge transformations method (CSGT/B3LYP/ 6-311+G**) 14 ; the larger basis set is necessary to get reasonably accurate results. NICS (ppm) calculations 15 were performed using the gauge independent atomic orbitals method (GIAO/B3LYP/6-31+G*). 16 For planar species, the ghost atom (Bq) was placed at the ring center, the standard NICS location (NICS[0]).…”

“…For the [9]annulenium cation, method E involves division of the ring into a 5C cationic piece and a 4C neutral piece. Last, for the [15]annulenium cation, method F is to divide the ring into a 9C cationic piece and a 6C neutral. In all cases, a CH 2 is added to each end of the ring fragments.…”