The synthesis of 2-bromo[6]helicene was revised and improved up to 51% yield. Its reactivity was thoroughly investigated, and a library of 17 different carbon, boron, nitrogen, phosphorus, oxygen and sulfur substituted derivatives was prepared. The racemization barrier for 2-bromo[6]helicene was determined, and the usage of enantiomers in the synthesis of optically pure helicenes was rationalized. The three most energy-demanding reactions using enantiomerically pure 2-bromo[6]helicene were tested in order to confirm the predicted enantiomeric excess.

of twisted arylamines into their respective o-diketones by aerial oxygen (Scheme 4D). 16 The reaction is self-catalytic; the arylamine sensitizes formation of singlet oxygen, which then oxidizes the amine-substituted double bond via [2 + 2]cycloaddition. This method was used for preparation of 5 different derivatives, including very densely functionalized tetraketones 19d and 19e.1.3. C−H Activation. Reactions proceeding via the activation of the C−H bond represent a very valuable approach to the preparation of new molecules since they require little to no presubstitution and can provide valuable helicene derivatives with high regioselectivity. An example of C−H borylation was published by Necǎs and co-workers (Scheme 5A). 30,31 They used an iridium catalyst for the introduction of a pinacolboronate group with certain regioselectivity toward positions 2 and 3 of the helicene. The [4]helicene 20a showed 65% isolated yield of both regioisomers in 2.8:1 ratio. Longer [5]helicene 20b showed increased yield (89%) and regioselectivity (8:1) after the authors opted for a different catalytic system than in the first example. Both isomers were separated using HPLC, and the authors further explored their reactivity in several Suzuki coupling reactions. The same transformation was accomplished on carbazole-based helicene 22, although with low yield (Scheme 5B).

No abstract

Functional DNAm olecules are useful components in nanotechnology and synthetic biology.T oexpand the toolkit of functional DNAp arts,i nt his study we used artificial evolution to identify ag lowing deoxyribozyme called Supernova. This deoxyribozyme transfers ap hosphate from a1 ,2dioxetane substrate to its 5' hydroxylg roup,w hich triggers ac hemiluminescent reaction and af lash of blue light. An engineered version of Supernova is only catalytically active in the presence of an oligonucleotide complementary to its 3' end, demonstrating that light production can be coupled to ligand binding.W eanticipate that Supernova will be useful in awide variety of applications,i ncluding as as ignaling component in allosterically regulated sensors and in logic gates of molecular computers.

A straightforward visible-light-promoted oxidation of aminohelicenes providing helical ortho-diketones is described. It is shown that the oxidation of amines proceeds via [2 + 2]cycloaddition reaction with singlet oxygen as an oxidizer and the reaction is specific to distorted aromatic systems. The versatility of the prepared diketones and tetraketones was proven in several heterocycle-forming reactions. The observed adjustment of the physicochemical properties of original molecules is valuable for further development of functional molecules based on helicenes.

No abstract

Functional DNAm olecules are useful components in nanotechnology and synthetic biology.T oexpand the toolkit of functional DNAp arts,i nt his study we used artificial evolution to identify ag lowing deoxyribozyme called Supernova. This deoxyribozyme transfers ap hosphate from a1 ,2dioxetane substrate to its 5' hydroxylg roup,w hich triggers ac hemiluminescent reaction and af lash of blue light. An engineered version of Supernova is only catalytically active in the presence of an oligonucleotide complementary to its 3' end, demonstrating that light production can be coupled to ligand binding.W eanticipate that Supernova will be useful in awide variety of applications,i ncluding as as ignaling component in allosterically regulated sensors and in logic gates of molecular computers.

Herein, a visible‐light photochemical approach for practical helicene functionalization at very mild reaction conditions is described. The photochemical reactions allow for the regiospecific and innate late‐stage functionalization of helicenes and are easily executed either through the activation of C(sp2)−Br bonds in helicenes using K2CO3 as inorganic base or direct C(sp2)−H helicene bond functionalization under oxidative photoredox reaction conditions. Overall, using these transformations six different functional groups are introduced to the helicene scaffold through C−C and four different C‐heteroatom bond‐forming reactions.