Synthesis,Characterization, and Electronic Structures of Porphyrins Fused with Polycyclic Aromatic Ring Systems

A series of porphyrins fused with acenaphthylene, phenanthroline, and benzofluoranthene polycyclic aromatic rings were prepared by means of a 3+1 porphyrin synthesis approach and subsequent retro‐Diels–Alder reaction of bicyclo[2.2.2]octadiene‐fused precursors. Analysis of the magnetic circular dichroism spectra and the results of time‐dependent DFT calculations are used to identify the reasons for the trends observed in the wavelengths and relative intensities of the Q bands of the products. Michl's perimeter model is used as a conceptual framework to explain the changes in the relative energies of the frontier π‐molecular orbitals.     

Multi-Stage Redox Systems Based on Dicationic P-Containing Polycyclic Aromatic Hydrocarbons

We report the straightforward synthesis of unprecedented electron-acceptors based on dicationic P-containing PAHs (Polycyclic Aromatic Hydrocarbons) based on copper mediated radical approach. In these systems, two phosphoniums are connected through various PAHs backbones. The impact of π-extension on both the optical and redox properties is investigated using a joint experimental (UV/Vis absorption, fluorescence and cyclic voltammetry) and theoretical approach (TD-DFT calculations). Finally, (spectro)-electrochemical studies prove that these compounds possess three redox states and EPR studies confirm the in situ formation of an organic radical delocalized on the PAH backbone.     

Synthesis of Polycyclic Aromatic Hydrocarbons Decorated by Fluorinated Carbon Acids/Carbanions

The carboarylation reaction of biphenyl-alkynes was successfully triggered by electrophilic attack of 1,1-bis(triflyl)ethylene on the alkyne moiety to give polycyclic aromatic hydrocarbons (PAHs) decorated by superacidic carbon acid functionality. Neutralisation of thus obtained acids with NaHCO₃ yielded the corresponding sodium salts, which showed improved solubility in both aqueous and organic solvents.     

Twisted Polycyclic Arenes from Tetranaphthyldiphenylbenzenes by Controlling the Scholl Reaction with Substituents

Herein, we report two new types of twisted polycyclic arenes ( 2 a , b and 3 a , b ) with constitutionally isomeric π‐backbones, which are synthesized by controlling the Scholl reaction of 1,2,4,5‐tetra(naphth‐2‐yl)‐3,6‐diphenylbenzene ( 1 ) with properly positioned electron‐donating substituents. With a polycyclic backbone containing two [5]helicene and four [4]helicene moieties, 2 a and b are new members of multiple helicenes with interesting stereochemistries. The as‐synthesized 2 a and b are the twisted isomers, and thermal isomerization of twisted‐ 2 b results in anti‐ 2 b , a more stable stereoisomer. Both twisted‐ and anti‐ 2 b have been fully characterized, and the thermal isomerization of twisted‐ 2 b has been studied with ¹H NMR spectroscopy and DFT calculations. Compounds 3 a and b are new members of twistacenes, the benzannulated pentacene backbone of which exhibits an end‐to‐end twist as found from the crystal structure. Twisted‐ and anti‐ 2 b are also found to function as p‐type semiconductors in solution‐processed thin film transistors, whereas the thin films of 3 b appear insulating presumably due to the lack of π–π interactions.     

Macrocyclic Transformations from Norrole to Isonorrole and an N‐Confused Corrole with a Fused Hexacyclic Ring System Triggered by a Pyrrole Substituent

Three kinds of fused porphyrinoids, L2 – L4 , possessing different types of corrole‐based frameworks were synthesized from a pyrrole‐substituted corrole isomer (norrole L1 ). Oxidation of L1 afforded a unique N‐C_meso‐fused pyrrolyl isonorrole L2 , involving the fusion of an auxiliary pyrrolic NH moiety with a meso‐sp³‐hybridized carbon atom. Subsequently, L2 underwent macrocycle transformations to give singly and doubly N‐C_Ar‐fused N‐confused corroles, L3 and L4 , respectively. L3 and L4 contain fused [5.7.6.5]‐tetra‐ and [5.6.7.7.6.5]‐hexacyclic structures, respectively, prepared through lateral annulation. These skeletal transformation reactions from norrole to its isomer isonorrole and finally to N‐confused corrole indicate that multiply fused porphyrinoids could be readily synthesized from pyrrole‐appended confused porphyrinoids.     

Cobalt(II) Porphyrin‐Catalyzed Intramolecular Cyclopropanation of N‐Alkyl Indoles/Pyrroles with Alkylcarbene: Efficient Synthesis of Polycyclic N‐Heterocycles

A protocol on chemoselective cobalt(II) porphyrin‐catalyzed intramolecular cyclopropanation of N‐alkyl indoles/pyrroles with alkylcarbenes has been developed. The reaction enables the rapid construction of a range of nitrogen‐containing polycyclic compounds in moderate to high yields from readily accessible materials. These N‐containing polycyclic compounds can be converted into a variety of N‐heterocycles with potential synthetic and biological interest. Compared to their N‐tosylhydrazone counterparts, the use of bulky N‐2,4,6‐triisopropylbenzenesulfonyl hydrazones as carbene precursors allows cyclopropanation to occur under milder reaction conditions.     

Synthesis of Bis(arylethynyl) Selenides by One‐Pot Protocol

An efficient method without using terminal arylacetylenes as substrates for the synthesis of bis(arylethynyl) selenides 1 (ArCC Se CC Ar) was described, and a series of compounds 1a−1m have been obtained by a one‐pot three‐step strategy from the corresponding bis(arylethanonyl) selenides. The mechanism was identified through trapping and characterization of a key intermediate 2a , and an elimination using it directly. The results from experiments indicated that the reaction procedure involves the formation of the enol phosphate and a subsequent base‐induced elimination.     

Anthocyanin Color Stabilization by Host-Guest Complexation with p-Sulfonatocalix[n]arenes

Flavylium-based compounds in their acidic and cationic form bring color to aqueous solutions, while under slightly acidic or neutral conditions they commonly bring discoloration. Selective host-guest complexation between water-soluble p-sulfonatocalix[n]arenes (SCn) macrocycles and the flavylium cationic species can increase the stability of the colored form, expanding its domain over the pH scale. The association constants between SCn and the cationic (acid) and neutral basic forms of flavylium-based compounds were determined through UV-Vis host-guest titrations at different pH values. The affinity of the hosts for synthetic chromophore was found to be higher than for a natural anthocyanin (Oenin). The higher affinity of SC4 for the synthetic flavylium was confirmed by ¹H NMR showing a preferential interaction of the flavylium phenyl ring with the host cavity. In contrast with its synthetic counterpart, the flavylium substitution pattern in the anthocyanin seems to limit the inclusion of the guest in the host’s binding pocket. In this case, the higher affinity was observed for the octamer (SC8) likely due to its larger cavity and higher number of negatively charged sulfonate groups.     

Silver‐Catalyzed Arylation of (Hetero)arenes by Oxidative Decarboxylation of Aromatic Carboxylic Acids

A long‐standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver‐catalyzed intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron‐deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho‐substituted aromatic carboxylic acids, which were a limitation of previously reported methods.     

Trifluoromethoxylation Reactions of (Hetero) arenes,Olefinic Systems and Aliphatic Saturated Substrates

Direct fluoroalkoxylation reactions of (hetero)arenes, carbon-carbon multiple bonds, and substitution reactions at Csp³ carbon centers by CF₃O, CHF₂O, and (CF₃)₂CFO groups are discussed. Emphasis on thermal radical, electron transfer, photocatalytic, electrochemical and redox-neutral radical methods are placed to accomplish fluoroalkoxylation reactions. All these methods employ either radical fluoroalkoxylating reagents or some nucleophilic trifluoromethoxylating sources of CF₃O. A summary of all these methods is provided in Table 2.     

Synthesis and Switching the Aromatic Character of Oxatriphyrins(2.1.1)

Triangularly shaped, contracted porphyrinoids belong to a group of molecules where the geometry significantly modifies the observed electronic properties. The need for a controllable, effective, and widely applicable approach to triphyrins drives extensive research towards macrocyclic materials that act as potential controlling motifs by switching their aromaticity. Two isomeric thiophene‐fused triphyrins(2.1.1) were synthesized by applying an innovative approach. Spectroscopic techniques (NMR, UV/Vis) show that both macrocycles are aromatic and quantitatively convert into anti‐aromatic structures after reduction with a zinc amalgam. The reduced forms were stabilized through boron(III) coordination, thereby allowing the observation of anti‐aromatic 16 π delocalization within a contracted porphyrin.     

Construction of Bridged Polycyclic Systems by Polyene Cyclization

A stereoselective construction of bridged tri‐ and tetracyclic systems embedded in some 3,5‐dimethylorsellinic acid (DMOA)‐derived meroterpenoids was achieved by exploiting a polyene cyclization of suitably functionalized epoxyallylsilanes. Both the olefinic substituent on the epoxide and allylic trimethylsilyl (TMS) group were found to play pivotal roles in the success of the present reaction. The fact that the cyclization of monocyclized byproducts did not proceed strongly suggests that the reaction could be a concerted transformation.     

1,4‐Bis(alkenyl)‐2,5‐dipiperidinobenzenes: Minimal Fluorophores Exhibiting Highly Efficient Emission in the Solid State

Minimum requirements : Crystals and thin films of 1,4‐bis(alkenyl)‐2,5‐dipiperidinobenzenes, which contain only one benzene ring as the aromatic component, emit visible light with excellent solid‐state quantum yields upon irradiation with UV light. Polystyrene thin films doped with the benzenes also exhibit brilliant fluorescence. By modifying the alkenyl groups, the emission color can be tuned in the range from blue to red.

     

Synthesis of Functionalized Dihydrobenzofurans by Direct Aryl C−O Bond Formation under Mild Conditions

A method for the synthesis of dihydrobenzofurans by a direct aryl C?O bond formation is described. A mechanistic pathway for the reaction, distinct from previously described similar transformations, allows for mild reaction conditions that are expected to be compatible with functionalized substrates.     

基于二芳炔硫醚的2,6-二芳基-1,4-二噻烯的合成

描述了一种基于二芳炔硫醚(Ar—C≡C—S—C≡C—Ar)底物合成2,6-二芳基-1,4-二噻烯的方法.将二芳炔硫醚和Na2S·9H2O在C2H5OH/C2H5ONa体系中回流反应,以80%~96%的产率合成了一系列2,6-二芳基-1,4-二噻烯化合物.该方法反应条件温和、产率高并且表现出很好的选择性.反应机理涉及硫负离子对底物分子的两个C≡C键的选择性亲核加成,即硫负离子(包括S2-和中间体B硫负离子)总是选择性地加到芳基一侧的炔碳上形成1,4-二噻烯.对化合物1a进行了X线晶体结构解析.分子中的六元杂环呈"船式"构型.C(1)—C(2)和C(1A)—C(2A)具有典型的双键性质,S(1)—C(2)和S(2)—C(1)的键长数则比一般C—S单键稍短,显示硫原子上的孤对电子与C(1)=C(2)双键上的π电子存在一定程度的共轭作用.1a的晶体学参数:属正交晶系,Pnma空间群,a=10.1330(11),b=27.318(3),c=5.5402(6),α=90.00°,β=90.00°,γ=90.00°,V=1533.6(3)3,Z=4,ρcalcd=1.422 g/cm3.最终偏离因子R=0.038,Rw=0.102。