Kazuhiro Miyawaki

Cycloaromatization of a non-conjugated polyenyne system: Synthesis of 5H-benzo[d]fluoreno[3,2-b]pyrans via diradicals generated from 1-[2-{4-(2-alkoxymethylphenyl)butan-1,3-diynyl}]phenylpentan-2,4-diyn-1-ols and trapping evidence for the 1,2-didehydrobenzene diradical

Non-conjugated tetraynes 1 undergo thermal intramolecular cyclization to non-benzenoid diradicals (23) followed by radical cycloaromatization at 25 °C to provide 7-dehydro-5H-benzo[d]fluoreno[3,2-b]pyran monoradical (24) and alkyl radicals (25). Hydrogen abstraction of 24 gives 5H-benzo[d]fluoreno[3,2-b]pyrans (3) which are converted to 4 by reaction with 25. On the other hand, 2 gives 5H-fluorenol (5), indicating the formation of 1,2-didehydrobenzene diradical intermediates (28 and 29). These radicals are trapped as the corresponding Diels-Alder-type products by reaction with an aromatic diene, anthracene.

Domino thermal radical cycloaromatization of non-conjugated aromatic hexa- and heptaynes: synthesis of fluoranthene and benzo[a]rubicene skeletons

Non-conjugated aromatic hexa- and heptaynes underwent domino thermal radical cycloaromatization at 25°C to yield indenol ring-fused fluoranthene and indenol ring-fused benzo[a]rubicene skeletons with helicity. This multi-cyclization reaction proceeded regioselectively to yield [6]helicene derivatives via annulation at the final step. The structure and thermal racemization of [6]helicene derivatives (6 and 7) is also described.

Multiple cycloaromatization of novel aromatic enediynes bearing a triggering device on the terminal acetylene carbon

Abstract Aromatic enediynes (1) bearing a triggering device on the terminal acetylene carbon undergo thermal cyclization at 25 °C to yield polyphenylene ring systems (6, 9, 13, and 15(16)) giving radical intermediates, dehydrobenzene monoradical (12) and didehydrobenzene biradicals (4 and 14) which may serve as a DNA-cleaving reagent.

Cyclodextrin polymers as highly effective adsorbents for removal and recovery of polychlorobiphenyl (PCB) contaminants in insulating oil.

A total of 179 countries (parties) ratified the Stockholm Convention on persistent organic pollutants (POPs) and agreed to destroy polychlorobiphenyls (PCBs) and develop a sound management plan by 2028. Currently, still 3 million tons of PCB-contaminated oil and equipment need to be managed under the Stockholm Convention. Thus, the development of a facile and environmentally benign method to treat large amounts of oil stockpiles contaminated with PCBs is a crucial subject. Herein, we report that cyclodextrin (CD) polymers, which are easily prepared by cross-linking the renewable cyclic oligosaccharide γ-cyclodextrin (γ-CD) with dibasic acid dichlorides, are a new selective and powerful adsorbent to remove PCB contaminants in oil. When PCB (100 ppm)-contaminated oil was passed through a column packed with the terephthaloyl-cross-linked γ-CD polymer (TP-γ-CD polymer) at 80-110 °C, the PCB contaminants were completely removed from the oil. Additionally, methyl esterification of the free carboxylic groups of the TP-γ-CD polymer enabled the complete recovery of the PCBs adsorbed on the polymer (with >99.9% recovery efficiency) by simply washing with acetone. The methyl-esterified TP-γ-CD polymer could be recycled at least 10 times for PCB adsorption without any loss in the adsorption capability. These results revealed that the γ-CD polymers can function as highly effective and powerful adsorbents for the removal and recovery of PCBs from PCB-contaminated oil and, thus, significantly contribute to the protection of the global environment.

6-O-Modified β-Cyclodextrin Enabling Inclusion Complex Formation in Nonpolar Media

Heptakis(6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (TBDMS-beta-CD) effectively forms inclusion complexes with chlorinated benzenes in nonpolar solvents such as benzene-d(6) and cyclohexane-d(12). The inclusion selectivity toward 1,2- and 1,3-dichlorobenzenes can be switched by changing the solvent from benzene-d(6) to cyclohexane-d(12). Moreover, 1,2,4-trichlorobenzene (90 ppm) is perfectly removed from insulating oil by using TBDMS-beta-CD as an adsorbent.

Synthesis and Properties of Functionalized [6] Helicenes by the Thermal Domino Radical Cycloaromatization of Acyclic Polyynes

Abstract Non-conjugated aromatic hexaynes and heptaynes undergo thermal domino radical cycloaromatization under mild conditions to yield indenol ring-fused fluoranthene and indenol ring-fused benzo[a]rubicene skeletons with helicity. The structure and thermal racemization of [6]helicene derivatives (12 and 13) are also described.