Electrochemical 1,2-Diarylation of Alkenes Enabled by Direct Dual C-H Functionalizations of Electron-Rich Aromatic Hydrocarbons.

A cobalt-promoted electrochemical 1,2-diarylation of alkenes with electron-rich aromatic hydrocarbons via direct dual C-H functionalizations is described, which employs a radical relay strategy to produce polyaryl-functionalized alkanes. Simply by using graphite rod cathode instead of platinum plate cathode, chemoselectivity of this radical relay strategy is shifted to the dehydrogenative [2+2+2] cycloaddition via 1,2-diarylation, annulation, and dehydrogenation cascades leading to complex 11,12-dihydroindolo[2,3-a]carbazoles. Mechanistical studies indicate that a key step for the radical relay processes is transformations of the aromatic hydrocarbons to the aryl sp2 -hybridized carbon-centered radicals via deprotonation of the corresponding aryl radical cation intermediates with bases.

Benzylic C-H heteroarylation of N-(benzyloxy)phthalimides with cyanopyridines enabled by photoredox 1,2-hydrogen atom transfer.

A visible light initiated α-C(sp3)-H arylation of N-(benzyloxy)phthalimides with cyanopyridines for the construction of highly valuable pyridinyl-containing diarylmethanols, including bioactive motif-based analogues, is reported. This method enables arylation of the C(sp3)-H bonds adjacent to an oxygen atom through alkoxy radical formation by O-N bond cleavage, 1,2-hydrogen atom transfer (HAT), arylation and C-CN bond cleavage cascades, and offers a means to exploit 1,2-HAT modes to incorporate functional groups for constructing functionalized alcohols.

2,6-Bis(4-meth-oxy-phen-yl)-1,4-dithiine.

The title mol-ecule, C18H16O2S2, reveals crystallographic twofold rotation symmetry (with both S atoms lying on the axis) and one half-mol-ecule defines an asymmetric unit. The dithiine ring is in a boat conformation. The aromatic ring and the C=C bond are nearly coplanar, with small torsion angles of -171.26 (19) and 8.5 (3)°. The two S-C bond lengths [1.7391 (19) and 1.7795 (18) Å] are shorter than single C-S bonds and longer than analogous C=S double bonds, which indicates a certain degree of conjugation between the lone pair on the S atom and π electrons of the C=C bond. The crystal packing only features van der Waals inter-actions.

5,11,17,23-Tetra-kis(1,1-di-methyl-eth-yl)-26,28-di-hydroxy-calix[4]arene-25,27-mono-thia-crown-3.

The title calix[4]arene compound [systematic name: 3,9,15,34-tetra-tert-butyl-19,29-dioxa-24-thia-hexa-cyclo-[15.13.7.1(7,11).1(32,36).0(5,30).0(13,18)]nona-triaconta-1(30),2,4,7,9,11(39),13,15,17,32,34,36(38)-dodeca-ene-38,39-diol], C52H70O4S, displays a cone-like conformation, the opposite arene rings bridged by the mono-thia-crown-3 unit are nearly parallel [dihedral angle = 16.01 (18)°], whereas the other opposite arene rings are twisted to each other at an angle of 74.41 (17)°. Intra-molecular O-H⋯O hydrogen bonds help to stabilize the mol-ecular structure. In the crystal, a C-H⋯π inter-action occurs. One of the tert-butyl groups is disordered over two sets of sites with a site-occupancy ratio of 0.70:0.30.

Cationic recognition by tert-butylcalix[4]arene-functionalized nanoprobes.

A nanoparticle-based strategy has been demonstrated using structurally-tailored tert-butylcalixarenes immobilized on gold nanoparticles to tune the guest access to the calixarene cone cavity for cationic recognition. This strategy exploits the interparticle charge-induced aggregation upon selective capture of metal cations into the nanoparticle-immobilized tert-butylcalixarenes, which produces calorimetric changes for the detection. A possible pathway for the binding of M(n+) into the t-BCA structure and the interparticle interaction is proposed for the formation of an electric double layer inducing the interparticle association responsible for the red-shifted surface plasmon resonance band of the nanoparticles. The value of this class of calorimetric nanoprobes will be in the area of designing advanced host-guest probes using a variety of calixarene ligands for ionic recognition in a simplistic detection format.

Molecularly-mediated assembly of gold nanoparticles with interparticle rigid, conjugated and shaped aryl ethynyl structures.

The rigidity, conjugation, and shape-persistent architectures of aryl ethynyls of V, Y, and X shapes serve as an ideal model system for defining interparticle structures, which have been demonstrated for the mediated assembly of gold nanoparticles.

Enantiopure double-helical phenylene ethynylene cyclophynes with the 2,2'-binaphthyl template.

New types of enantiopure compounds were synthesized to gain better insight into the structural features of phenylene ethynylene cyclophynes. Besides the previously obtained meta-substituted arylene ethynylenes, 1, ortho-connected phenylene ethynylene units were incorporated to give cyclophynes with ortho/meta and ortho/ortho connection modes, 2 and 3. Furthermore, a diphenylethyne component was also accommodated in 4. Both ab initio calculations and NMR spectra suggest a large amount of strain for 2 but less strain for 3 and 1 a, the latter having the smallest ring size among cyclophynes with the meta/meta connection mode. The CD spectra of 2 and 3 showed a characteristic shoulder at around 340 nm, similar to the case of 1 a. This implies that the aromatic acetylene bonds cross over each other in the double-helical structure. These results indicate that chirality information is useful for probing the persistency of molecular shape.

Organotin perfluorooctanesulfonates as air-stable Lewis acid catalysts: synthesis, characterization, and catalysis.

The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and dialkyltin dihalides with silver perfluorooctanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. 119Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of superoxide/metal-ion complexes. In contrast to well-known organotin triflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carbon-carbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.

Metal-assisted assembly of pyridine-containing arylene ethynylene strands to enantiopure double helicates.

Pyridine-containing arylene ethynylene strands were connected to the 2- and 2'-positions of (R)- and (S)-1,1'-binaphthyl templates. The arylene ethynylene moieties underwent intramolecular coordination with Ag(I) or Cu(I) ion to afford enantiopure double helicates. The double-helical structure was elucidated on the basis of circular dichroic (CD) spectra. The importance of intramolecular complexation of the double strands for the helicate formation was confirmed by comparison with a ligand bearing a single strand. Connection of the strands through an ether linkage enabled a sorting out of the Cotton effect induced by double-helical arylene ethynylene moieties. The CD exciton chirality method unambiguously proved that the termini of the strands approach each other upon complexation and that the sense of the induced helicity is the same as predicted by molecular modeling.

Sulfoximine version of double elimination protocol for synthesis of chiral acetylenic cyclophanes.

A new strategy for constructing enantiopure acetylenic cyclophanes is described on the basis of one-pot double elimination reaction starting from dialdehydes and bis(sulfoximine)s. In this case, the conventional sulfone protocol affords poorer yields of the desired cyclophanes. Thus, arylene-ethynylene moieties with terminal sulfoximine or formyl functions are linked to binaphthyl cores and these building blocks are then subjected to double elimination reaction. The desired macrocycles are obtained in up to 35 % yield. The corresponding Sonogashira coupling fails to afford cyclophanes indicative of effectiveness of the double elimination methodology.