Evaluation of Tin−Oxygen Bond Association by Means of ab Initio Molecular Orbital Calculations

Ab initio calculations with MP2 provide reliable information about structure and bonding of organotin molecules. The association behavior of organotin alkoxides is counterbalanced by conflicting enthalpy and entropy contributions. The increase in Lewis acidity of tin induced by attachment of alkoxy group(s) is of prime importance for the association. On the other hand, formation of the stable dimeric distannoxanes has been proved by great negative ΔG values. The oxygen atom between the tin atoms in distannoxanes has stronger Lewis basicity than that in organotin alkoxides. The multiplier effect of both Lewis acidity of tin and Lewis basicity of oxygen is reflected on the shortening of the secondary Sn−O bond. As a whole, tin−oxygen bonds have been successfully elucidated for the first time by ab initio calculations

DFT Study on Activation of Carbon Dioxide by Dimethytin Dimethoxide for Synthesis of Dimethyl Carbonate

DFT calculations put forth theoretical grounds for a smooth reaction between methoxy and carbonate groups on the organotin template to afford dimethyl carbonate (DMC). The strong association of the Sn−O bond is the driving force for facile synthesis of DMC with organotin alkoxides. On the dimeric template, the methoxy and carbonate groups can be arranged in a proximate position to acquire an entropic gain only when they are bonded to separate tin atoms. The strong Sn−O bond association also plays a crucial role in driving the process to the final stage. The great stability of the distannoxane dimer formed in the final stage can outweigh all thermodynamic disadvantages involved in the previous steps

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

Stereogenic Motif Consisting of Rigid Ring and Intraannular Chains: Isolation and Structures of Stereoisomers of 9-Alkyl-1,8-anthrylene−Butadiynylene Cyclic Dimers

Stereoisomers of the title π-conjugated compounds with intraannular propyl and butyl groups were isolated by chromatography. The high barrier to isomerization is attributed to the steric hindrance between the alkyl chains and the rigid framework

Stereogenic Motif Consisting of Rigid Ring and Intraannular Chains: Isolation and Structures of Stereoisomers of 9-Alkyl-1,8-anthrylene−Butadiynylene Cyclic Dimers

Stereoisomers of the title π-conjugated compounds with intraannular propyl and butyl groups were isolated by chromatography. The high barrier to isomerization is attributed to the steric hindrance between the alkyl chains and the rigid framework

Dual Emission and Mechanofluorochromism of a V‑Shaped π‑System Composed of Disulfonyl-Substituted Dibenzocyclooctatetraenes

A series of dibenzocyclooctatetraenes 6 bearing phenylethynyl and phenylsulfonyl groups were synthesized from bromo-substituted formylbenzyl sulfone 4 via cyclic dimerization of 4 and Sonogashira coupling of the resulting dibromocyclooctatetraene 3 with terminal acetylenes. The diamino derivative 6b exhibited dual emission with emission maxima at 436 and 547 nm. Furthermore, in the fluorescence of 6b, solvatofluorochromism was observed in response to solvent polarity, whereas in the solid states, mechanofluorochromism was observed

Visible Light and Hydroxynaphthylbenzimidazoline Promoted Transition-Metal-Catalyst-Free Desulfonylation of <i>N-</i>Sulfonylamides and <i>N-</i>Sulfonylamines

A visible light promoted process for desulfonylation of <i>N-</i>sulfonylamides and -amines has been developed, in which 1,3-dimethyl-2-hydroxynaphthyl­benzimidazoline (HONap-BIH) serves as a light absorbing, electron and hydrogen atom donor, and a household white light-emitting diode serves as a light source. The process transforms various <i>N-</i>sulfonylamide and -amine substrates to desulfonylated products in moderate to excellent yields. The observation that the fluorescence of 1-methyl-2-naphthoxy anion is efficiently quenched by the substrates suggests that the mechanism for the photoinduced desulfonylation reaction begins with photoexcitation of the naphthoxide chromophore in HONap-BIH, which generates an excited species via intramolecular proton transfer between the HONap and BIH moieties. This process triggers single electron transfer to the substrate, which promotes loss of the sulfonyl group to form the free amide or amine. The results of studies employing radical probe substrates as well as DFT calculations suggest that selective nitrogen–sulfur bond cleavage of the substrate radical anion generates either a pair of an amide or amine anion and a sulfonyl radical or that of an amidyl or aminyl radical and sulfinate anion, depending on the nature of the <i>N-</i>substituent on the substrate. An intermolecular version of this protocol, in which 1-methyl-2-naphthol and 1,3-dimethyl-2-phenyl­benzimidazoline are used concomitantly, was also examined

One-Shot Double Amination of Sondheimer–Wong Diynes: Synthesis of Photoluminescent Dinaphthopentalenes

Photoluminescent diamino-substituted dinaphtho­pentalenes were synthesized successfully by the treatment of <i>in situ</i> prepared dinaphtho­cyclo­octadiyne with lithium amide. This reaction involves a series of transformations including the nucleophilic addition of the lithium amide to a triple bond of the cyclooctadiyne moiety, transannulation, protonation of the resulting pentalene anion, and the nucleophilic substitution of the pentalene core with the lithium amide. In this procedure, a novel double amination step plays a key role. When the diamino-substituted dinaphtho­pentalenes were irradiated with UV light in toluene, fluorescence was observed at around 580 nm (Φ_F < 0.03)

One-Shot Double Amination of Sondheimer–Wong Diynes: Synthesis of Photoluminescent Dinaphthopentalenes

Photoluminescent diamino-substituted dinaphtho­pentalenes were synthesized successfully by the treatment of <i>in situ</i> prepared dinaphtho­cyclo­octadiyne with lithium amide. This reaction involves a series of transformations including the nucleophilic addition of the lithium amide to a triple bond of the cyclooctadiyne moiety, transannulation, protonation of the resulting pentalene anion, and the nucleophilic substitution of the pentalene core with the lithium amide. In this procedure, a novel double amination step plays a key role. When the diamino-substituted dinaphtho­pentalenes were irradiated with UV light in toluene, fluorescence was observed at around 580 nm (Φ_F < 0.03)