We herein report the reactivity and regioselectivity of 2-pyrenyl as a coupling unit in Scholl reactions.On the basis of the Scholl reactions of hexaarylbenzene substrates,we have found that pyrenyl units are preferab...We herein report the reactivity and regioselectivity of 2-pyrenyl as a coupling unit in Scholl reactions.On the basis of the Scholl reactions of hexaarylbenzene substrates,we have found that pyrenyl units are preferably oxidized over naphthyl and phenyl units under appropriate Scholl reaction conditions,allowing divergent synthesis through a highly controllable intramolecular coupling sequence.We find that the C1 and C3 positions of the 2-pyrenyl unit are the favorable sites for intramolecular coupling while C4 is not reactive to allow further coupling.The reactivity and regioselectivity pattern can be explained by the spin density distribution,which shows that carbon-carbon bonds preferably form at sites with higher positive spin density.Guided by these findings,we successfully synthesized a double helicene and a sextuple helicene through the controlled Scholl reactions of 2-pyrenyl units.展开更多
Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped p...Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped paraphenylene precurso rsto 2,11,18,27-tetrabromooctabenzo[8]circulene and the subsequent intramolecular Yamamoto coupling and reductive aromatization reactions.The flexible nature of octabenzo[8]circulene enabled two different ways of connection in the Yamamoto coupling reactions,leading to the two constitutional isomers.The D2 isomer is shaped like a figure eight,as revealed by X-ray crystallography,and is resolved into two enantiomers by chiral HPLC.The synthesis of the C2v isomer is regarded as a further step toward precision synthesis of carbon schwarzites through a bottom-up approach.展开更多
基金supported by the University Grants Committee(Hong Kong)through a Research Matching Grant,Deutsche Forschungsgemeinschaft(DFG)through the research training group“Template-Designed Organic Electronics(TIDE)”(RTG 2591)the U.S.Department of Energy(DOE),Office of Science,Basic Energy Sciences(BES),Materials Sciences and Engineering Division under contract no.DE-AC02-05-CH11231(Nanomachine program KC1203)and contract no.DE-SC0023105.
文摘We herein report the reactivity and regioselectivity of 2-pyrenyl as a coupling unit in Scholl reactions.On the basis of the Scholl reactions of hexaarylbenzene substrates,we have found that pyrenyl units are preferably oxidized over naphthyl and phenyl units under appropriate Scholl reaction conditions,allowing divergent synthesis through a highly controllable intramolecular coupling sequence.We find that the C1 and C3 positions of the 2-pyrenyl unit are the favorable sites for intramolecular coupling while C4 is not reactive to allow further coupling.The reactivity and regioselectivity pattern can be explained by the spin density distribution,which shows that carbon-carbon bonds preferably form at sites with higher positive spin density.Guided by these findings,we successfully synthesized a double helicene and a sextuple helicene through the controlled Scholl reactions of 2-pyrenyl units.
基金supported by the General Research Fund 14300919 from the Research Grant Council of Hong Kong and a Research Matching Grant from the University Grants Committee(Hong Kong).
文摘Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped paraphenylene precurso rsto 2,11,18,27-tetrabromooctabenzo[8]circulene and the subsequent intramolecular Yamamoto coupling and reductive aromatization reactions.The flexible nature of octabenzo[8]circulene enabled two different ways of connection in the Yamamoto coupling reactions,leading to the two constitutional isomers.The D2 isomer is shaped like a figure eight,as revealed by X-ray crystallography,and is resolved into two enantiomers by chiral HPLC.The synthesis of the C2v isomer is regarded as a further step toward precision synthesis of carbon schwarzites through a bottom-up approach.
