Language：English   Publishing type：Research paper (scientific journal)  

We have achieved the enantioselective synthesis of axially chiral figure-eight spiro[9.9]cycloparaphenylene (CPP) tetracarboxylates with up to 75:25 er via the cationic Rh(I)/(R)-H8-BINAP complex-catalyzed chemo-, regio-, and enantioselective intermolecular double [2 + 2 + 2] cycloaddition of an achiral symmetric tetrayne with dialkyl acetylenedicarboxylates followed by reductive aromatization. The spiro[9.9]CPP tetracarboxylates are highly distorted at the phthalate moieties with large dihedral and boat angles and exhibit weak aggregation-induced emission enhancement behavior.

DOI： 10.1021/acs.orglett.3c00895

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s44160-023-00318-2

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Other Link： https://www.nature.com/articles/s44160-023-00318-2

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s44160-023-00268-9

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Other Link： https://www.nature.com/articles/s44160-023-00268-9

Language：English   Publishing type：Research paper (scientific journal)  

Planar chiral [2.2]cyclophanes with two aromatic rings in close proximity have attracted much attention for their applications as chiral materials and catalysts because of their stable chirality and transannular interactions. Although numerous [2.2]cyclophanes have been synthesized to date, only a few polycyclic aromatic hydrocarbon (PAH)-based ones have been reported, and the simultaneous control of two planar chiralities of the two aromatic rings facing each other has not been achieved. Here we report the enantio- and/or diastereoselective synthesis of planar chiral PAH-based [2.2]cyclophanes ([2.2]triphenylenophanes) via the high-yielding base-mediated intermolecular macrocyclization and Rh- or Ni-catalyzed intramolecular double [2 + 2 + 2] cycloadditions. DFT calculations have revealed that the second [2 + 2 + 2] cycloaddition kinetically determines the diastereoselectivity. Single crystal X-ray diffraction analyses have confirmed that the facing triphenylene or [5]helicene skeletons strongly repel each other, resulting in curved structures with bulged centers.

DOI： 10.1039/d3sc00571b

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acscatal.2c04740

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

The lateral π‐extension of helicenes would yield interesting physical properties derived from the enhanced π‐stacking ability as well as intrinsic helical chirality. Here we report the regiodivergent synthesis of hexabenzocoronene (HBC)‐based [6]helicenes via cationic rhodium(I)/segphos complex‐mediated intramolecular [2+2+2] and [2+1+2+1] cycloadditions of triynes followed by Scholl reaction. The resulting HBC‐based [6]helicenes possess stable helical chirality but more planar structure than previously reported HBC‐based [7] and [9]helicenes. Therefore, these HBC‐based [6]helicenes exhibit π‐stacking‐induced chiral self‐recognition in solution, allowing the measurement of enantiomeric ratios by¹H NMR spectroscopy without any chiral additive.

DOI： 10.1002/ejoc.202200690

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ejoc.202200690

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Axially chiral styrene‐carboxylic esters were synthesized in high yields with excellent enantioselectivity by the cationic rhodium(I)/H₈‐BINAP complex‐catalyzed chelation‐controlled [2+2+2] cycloaddition reactions of 1,6‐ and 1,7‐diynes with 1,3‐enyne‐carboxylic esters. The diastereo‐ and enantioselective synthesis of C₂ symmetric axially chiral cis and trans‐stilbene‐dicarboxylic esters was also achieved by the double [2+2+2] cycloaddition reactions of two molecules of the 1,6‐diyne with 2,3‐dialkynylmaleate and 2,3‐dialkynylfumarate, respectively. In these reactions, the 1,3‐enyne‐carboxylic esters coordinating to rhodium with a five‐membered chelate were more reactive than those coordinating to rhodium with a six‐membered chelate, although both chelation modes realized excellent enantioselectivity. The enantioselection mechanism of the cationic rhodium(I)‐catalyzed chelation‐controlled [2+2+2] cycloaddition was elucidated by DFT calculations.

DOI： 10.1002/anie.202202542

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202202542

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

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We report the synthesis of a [20]cyclophenacene‐type cyclophenylene‐naphthylene (CPN) belt and the enantioselective synthesis of chiral‐type CPN belts (up to >99 %ee) by the cationic rhodium(I)‐catalyzed intramolecular [2+2+2] cycloaddition of naphthalene‐embedded cyclic polyynes. The synthesis of a depth‐expanded CPN belt was also attempted, but the final intramolecular [2+2+2] cycloaddition was unsuccessful. Theoretical calculations clarified that the reactivity depends on the stability of the transition state in the initial oxidative cycloaddition step which is subject to molecular strain. The cylindrical structures of these CPN belts were confirmed by X‐ray crystallographic analyses. As a result of π‐extension through the introduction of naphthalenes in the chiral‐type CPN belts, the anisotropy dissymmetry factors of electronic circular dichroism and circularly polarized luminescence are amplified compared with the corresponding zigzag‐type chiral cyclophenylene belts.

DOI： 10.1002/anie.202200800

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202200800

Language：English   Publishing type：Research paper (scientific journal)  

The 1,3-diethoxycarbonyl-2,4,5-trimethylcyclopentadienyl (CpE) rhodium(III) complex displayed high efficacy in the catalytic oxidative annulation of 1-naphthols with internal alkynes under mild conditions. DFT calculations revealed that lower activation energies for the concerted metalation-deprotonation and the reductive elimination steps are the key to improved reactivity.

DOI： 10.1039/d1ob02181h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

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The enantioselective synthesis of aza[6] and [7]helicene‐like molecules have been achieved by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex‐catalyzed intramolecular [2+2+2] cycloaddition of cyanodiynes. This protocol was successfully applied to the diastereo‐ and enantioselective synthesis of an S‐shaped double aza[6]helicene‐like molecule with a high ee value of 89 %. Although no epimerization and racemization were observed in the double carbo[6]helicene‐like molecule at 80 °C, epimerization and racemization of the double aza[6]helicene‐like molecule proceeded at 80 °C. This double aza[6]helicene‐like molecule showed good fluorescent quantum yields and chiroptical responses under both neutral and acidic conditions.

DOI： 10.1002/chem.202005479

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.202005479

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>The perfectly diastereo- and enantiocontrolled catalytic synthesis of a cycloparaphenylene with four helical and two planar chiralities showing good chiroptical responses was achieved by the rhodium-catalyzed alkyne cyclotrimerization.</p>

DOI： 10.1039/d1sc00861g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

The enantioselective synthesis of polycyclic aromatic hydrocarbon (PAH)‐based planar chiral cyclophanes was achieved for the first time by the rhodium‐catalyzed intramolecular regio‐ and enantioselective [2+2+2] cycloaddition of tethered diyne‐benzofulvenes followed by stepwise oxidative transformations. The thus synthesized planar chiral bent cyclophanes, that possess bent p‐terphenyl‐ and 9‐fluorenone‐cores, were converted to 9‐fluorenol‐based ones with excellent ee values of &gt;99 % by diastereoselective 1,2‐reduction. These 9‐fluorenol‐based cyclophanes exhibited high fluorescence quantum yields, which were significantly higher than that of an acyclic reference molecule (78–82 % vs. 48 %). The bending effect on the chiroptical property was also examined, which revealed that the anisotropy factors (g_abs values) for electronic circular dichroism (ECD) of these 9‐fluorenol‐based planar chiral bent cyclophanes increase as the tether length becomes shorter.

DOI： 10.1002/chem.202001450

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.202001450

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Single and double cyclophenylene–ethynylenes (CPEs) with axial and helical chirality have been synthesized by the Sonogashira cross‐coupling of di‐ and tetraethynyl biphenyls with a U‐shaped prearomatic diiodoparaphenylene followed by reductive aromatization. X‐ray crystallographic analyses and DFT calculations revealed that the CPEs possess highly twisted bent structures. Bend angles on the edge of the paraphenylene units were close to the value of [5]cycloparaphenylene (CPP)—the smallest CPP to date. The double and single CPEs possessed stable chirality despite flexible biphenyl structures because of the high strain in the diethynyl–paraphenylene moiety. In both the single and double CPEs, orbital interactions along the biphenyl axis were observed by DFT calculations in LUMO and LUMO+2 of the single CPE and LUMO+1 of the double CPE, which likely cause lowering of these orbital energies. Concerning chiroptical properties: boosting of the g_abs value was observed in the biphenyl‐based double CPE, as well as the binaphthyl‐based single CPE, compared to the biphenyl‐based single CPE.

DOI： 10.1002/anie.202006959

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202006959

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jacs.0c03684

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

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It has been established that a newly developed cyclopentadienyl rhodium(III) [Cp^ARh^III] complex, bearing an acidic secondary amide moiety on the Cp ring, is able to catalyze the ortho‐bromination of O‐phenyl carbamates with N‐bromosuccinimide (NBS) at room temperature. The presence of the acidic secondary amide moiety on the Cp^A ligand accelerates the bromination by the hydrogen bond between the acidic NH group of the Cp^A ligand and the carbonyl group of NBS.

DOI： 10.1002/chem.202000253

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.202000253

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

The smallest spherical carbon nanocage so far, [2.2.2]carbon nanocage, has been synthesized by the cationic rhodium(I)/H₈‐binap complex‐catalyzed regioselective intermolecular cyclotrimerization of a cis‐1‐ethynyl‐4‐arylcyclohexadiene derivative followed by the triple Suzuki–Miyaura cross‐couplings with 1,3,5‐triborylbenzene and reductive aromatization. This cage molecule is highly strained, and its ring strain is between those of [6] and [5]cycloparaphenylenes. A significant red‐shift of an emission maximum was observed, compared with that of known [4.4.4]carbon nanocage. The sequential cyclotrimerizations of a cis‐1,4‐diethynylcyclohexadiene derivative with the same rhodium(I) catalyst followed by reductive aromatization failed to afford [1.1.1]carbon nanocage; instead, a β‐graph‐shaped cage molecule was generated.

DOI： 10.1002/anie.201903422

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.201903422

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Event date： 2021.8

Presentation type：Poster presentation  

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Event date： 2021.7

Presentation type：Poster presentation  

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Event date： 2021.3

Presentation type：Oral presentation (general)  

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Event date： 2020.12

Presentation type：Oral presentation (general)  

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Event date： 2020.3

Presentation type：Oral presentation (general)  

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Event date： 2019.10

Presentation type：Poster presentation  

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Event date： 2019.9

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Event date： 2019.6

Presentation type：Poster presentation  

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Event date： 2019.3

Presentation type：Oral presentation (general)  

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