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Tetraaminothiacalixarene 3, bearing four amino groups instead of the hydroxy groups of p-tert-butylthiacalix[4]arene 2, exhibits inclusion properties different from those of compound 2 towards small organic molecules upon crystallisation from neat solvents or guest solutions. X-ray crystallographic analyses reveal that nitromethane and acetonitrile are included into the cone-shaped cavity of compound 3, as is often seen in inclusion crystals of compound 2, whereas dichloromethane occupies a space between two distal benzene rings of compound 3, adopting a 1,3-alternate conformation. Acetic acid, which forms a dimer, fills a pore surrounded by four host molecules with a pinched cone conformation. Furthermore, guest-free crystals of compound 3 with a 1,3-alternate conformation absorb acetonitrile to give inclusion crystals with the same crystal structure as that obtained by the crystallisation. Thus, compound 3 flexibly changes its conformation according to the structures of guest compounds.

Heterogeneous self-assembly of thiacalix[4]arene-p-tetrasulfonate (TCAS), Ag(I), and Ln(III) (= Nd(III), Yb(III)) in aqueous solutions conveniently afforded ternary complexes emitting Ln(III)-centered luminescence in the near-infrared (NIR) region. A solution-state study revealed that the Ag(I)-Nd(III)-TCAS system gave a complex Ag(I)(4)·Nd(III)·TCAS(2) in a wide pH range of 6-12. In contrast, the Ag(I)-Yb(III)-TCAS system gave Ag(I)(2)·Yb(III)(2)·TCAS(2) at a pH of around 6 and Ag(I)(2)·Yb(III)·TCAS(2) at a pH of approximately 9.5. The structures of the Yb(III) complexes were proposed based on comparison with known Ag(I)-Tb(III)-TCAS complexes that show the same self-assembly behavior. In Ag(I)(2)·Yb(III)(2)·TCAS(2), two TCAS ligands sandwiched a cyclic array of a Ag(I)-Ag(I)-Yb(III)-Yb(III) core. In Ag(I)(2)·Yb(III)·TCAS(2), Yb(III) was accommodated in an O(8) cube consisting of eight phenolate O(-) groups from two TCAS ligands linked by two S-Ag-S linkages. Crystallographic analysis of Ag(I)(4)·Nd(III)·TCAS(2) revealed that the structure was similar to Ag(I)(2)·Yb(III)·TCAS(2) but that it had four instead of two S-Ag-S linkages. The number of water molecules coordinating to Ln(III) (q) estimated on the basis of the luminescent lifetimes was as follows: Ag(I)(4)·Nd(III)·TCAS(2), 0; Ag(I)(2)·Yb(III)(2)·TCAS(2), 2.4; and Ag(I)(2)·Yb(III)·TCAS(2), 0. These findings were compatible with the solution-state structures. The luminescent quantum yield (Φ) for Ag(I)(4)·Nd(III)·TCAS(2) was 4.9 × 10(-4), which is the second largest value ever reported in H(2)O. These findings suggest that the O(8) cube is an ideal environment to circumvent deactivation via O-H oscillation of coordinating water. The Φ values for Ag(I)(2)·Yb(III)(2)·TCAS(2) and Ag(I)(2)·Yb(III)·TCAS(2) were found to be 3.8 × 10(-4) and 3.3 × 10(-3), respectively, reflecting the q value. Overall, these results indicate that the ternary systems have the potential for a noncovalent strategy via self-assembly of the multidentate ligand, Ln(III), and an auxiliary metal ion to obtain a highly efficient NIR-emissive Ln(III) complex that usually relies on elaborate covalent linkage of a chromophore and multidentate ligands to expel coordinating water.

Reactions of Ph2HSiC≡CSiHPh2 with 2 equiv of the labile complexes Cp*(CO)2M(NCMe)Me (1a, M ═ W; 2, M ═ Mo; Cp* ═ η5-C5Me5) gave the novel CC-bridged dinuclear complexes Cp*(CO)2M(SiPh2)(μ-CC)(SiPh2...

Powdery crystals of p-tert-butylthiacalix[4]arene (2) selectively include EtOH from 1:1 mixtures of MeOH-EtOH and EtOH-PrOH, and EtCO(2)H from HCO(2)H-EtCO(2)H. On the other hand, no acid is included from HCO(2)H-MeCO(2)H, even though MeCO(2)H is included from the neat acid. The origins of these phenomena are discussed based on X-ray analysis of inclusion crystals prepared separately by crystallization.

A new acetylide−silylene complex, Cp*(CO)2W(SiPh2)(CCSiMe3) (4), was synthesized by the reaction of Cp*(CO)2W(NCMe)Me with Ph2HSiC≡CSiMe3. Complex 4 reacted with acetone to give the six-membered cy...

The electronic structure of a water-soluble near-infrared (NIR)-absorbing complex was determined to be singlet diradical [PtII(LISQ)2]2– [(LISQ)2–· = o-diiminosulfobenzosemiquinonate radical] by X-ray diffraction and 1H NMR spectroscopy. Cyclic voltammetry (CV) showed redox reactions of [PtII(LISQ)2]2– to give [PtII(LISQ)(LIBQ)]– (E1 = –0.26 V vs. Fc+/Fc) and [PtII(LISQ)(LPDI)]3– (E2 = –1.46 V) [(LIBQ)– = o-diiminosulfobenzoquinonate, (LPDI)3– = o-phenylenediiminesulfonate]. The monoradical structure of the latter was confirmed by electron paramagnetic resonance (EPR) spectroscopy. Splitting of the reduction wave of [PtII(LISQ)(LIBQ)]– in CV and the weak EPR signal suggested the formation of a dimer. Because the rest potential of the solution exceeds Epa1 at pH 4.0, the decrease in the NIR absorption at pH

The synthesis, X-ray and spectroscopic analysis, and unusual bonding and structure among heavy group-14 element congeners of allene (heavy allenes) [R(2)M=M'=MR(2); M = M' = Si (1a), M = Si, M' = Ge (1b), M = Ge, M' = Si (1c), and M = M' = Ge (1d)] are comparatively discussed. Using DFT calculations and PMO theory, the origin of the bent and fluxional skeleton of the heavy allenes is ascribed to the Jahn-Teller distortion associated with the effective pi-sigma* mixing (pi-sigma* distortion). This type of distortion is suggested to be a key concept for qualitative description of the unusual bonding of unsaturated compounds of heavy main-group elements.

We have investigated that photoreactivities of a series of diynediammonium dienecarboxylates in the crystalline state. In the case of 4,4′-butadiynedibenzylammonium disorbate, almost all diene moieties were polymerized during photoirradiation for 8 h. On the other hand, the conversion of diyne moieties was still low. Crystal structure of the monomer crystal indicates that the alignment of diene moieties is very similar to those of topochemically polymerizable crystals of diene derivatives. Even though the translation distance of diyne moieties is also suitable for the polymerization, the tilt angle is different from the ideal angle. It is the reason why the conversion of diyne moieties was low. By X-ray single-crystal structure analysis of the polymer crystal, we confirmed that the polymerization proceeded via topochemical reaction mechanism indeed. On the other hand, photodimerization of diene moieties in the crystals of 2,4-hexadiyne-1,6-diammonium (E,E)-muconate occurred because of the face-to-face ali...

4-Hydroxy-prolinamide alcohol with different noncoordination sites as a molecule showed excellent asymmetric catalytic activity in both the Michael reaction (up to 98% ee) and the direct aldol reaction (up to >99% ee), and the catalyzing reactions with high enantioselectivity are supported by a DFT theoretical study of their transition state.

Single-crystal X-ray diffraction studies of [K(1·3H)]·2MeOH complex obtained from p-tert-butylthiacalix[4]arene (1·4H) with KH, which shows two dimer formations. One of the dimers is formed by a hydrophobic interaction between each tert-butyl group of 1·3H and the cavity of another 1·3H in the crystalline state. The other dimer made metal coordination S⋯K⋯(O,S,O) between neighboring 1·3H and potassium ion. In the overall structure, this complex indicates non-porous structure and the adsorption capabilities toward gaseous organic molecules.

Ethynylsilyllithiums [R1R2(R3CC)SiLi: R1 = R2 = t-BuMe2Si, R3 = Me3Si (5a); R1 = R2 = t-BuMe2Si, R3 = Ph (5b); R1 = R2 = R3 = Me3Si (5c); R1 = t-BuMe2Si, R2 = Ph, R3 = Me3Si (5d); R1 = t-BuMe2Si, ...

Thermal reaction of alkynyl propargyl sulfoxides 1 afforded novel highly reactive (α-ketovinyl)thioketenes 3. Trapping experiments using a primary or secondary amine, formation of furanophane 4, through head-to-tail type dimerization, as well as direct observation using 1H NMR elucidated the generation pathway of 3 through sequential [2,3]/[3,3] sigmatropic rearrangement.

β-(N,N-Dimethylcarbamoylselenenyl)- and β-(N,N-dimethylcarbamoyltellurenyl)alkenyl ketones were converted into isoselenazoles and isotellurazole Te-oxides, respectively, simply by treating with hyd...

New di- (2) and tetracarboxylate ligands (4) were prepared on a sulfonylcalix[4]arene platform by O-alkylation of thiacalix[4]arene with ethyl bromoacetate, followed by hydrolysis of the ester function and oxidation of the sulfide bridges. The sulfonyl-based ligands 2 and 4 formed luminescent 1:1 complexes with terbium(III) ion having higher luminescent quantum yield (Φ = 0.291 and 0.287, respectively) than 1:1 complexes of the corresponding thiacalix[4]arene-based di- (1) and tetracarboxylate ligands (3) (Φ = 0.038 and 0.003, respectively), implying higher efficiency of sulfonyl ligands (2 and 4) than those of thia ligands (1 and 3) in the energy transfer process.

A number of the distinctive reactions of trisilaallene 1 and 2-germadisilaallene 4 with various reagents including water, alcohols, acetone, and haloalkanes were studied. The addition reactions of 1 to water and alcohols occur in a regiospecific manner to afford 1,3-dioxytrisilanes in high yields. The additions are explained by a stepwise mechanism involving the initial nucleophilic attack of a hydroxy oxygen to a terminal allenic silicon to give an intermediate unsymmetric disilene. The regiospecificity is rationalized by the shape of the frontier molecular orbitals and the NPA charge distribution of trisilaallene 1 and the intermediate disilene.

The reaction of the donor-stabilized silylene complex cis -Cp ∗ (CO) 2 (H)W SiHPh · THF ( 3 , Cp ∗ = η 5 -C 5 Me 5 ) with LiAlH 4 followed by the protonation of the resulting Li[Cp ∗ (CO) 2 W(H)(SiH 2 Ph)] ( 4 ) with excess CF 3 COOH afforded the trihydride complex Cp ∗ (CO) 2 WH 3 ( 6 ). The structure of 6 was characterized using variable-temperature NMR studies and X-ray crystal analysis. Deprotonation of 6 with KH gave the anionic dihydride complex K[Cp ∗ (CO) 2 WH 2 ] ( 7 ), which was converted into the dichlorosilyl dihydride complex Cp ∗ (CO) 2 W(H) 2 (SiHCl 2 ) ( 8 ) on treatment with trichlorosilane. The X-ray crystal analysis of 8 revealed that it adopts a distorted pseudo-octahedral structure with a short W–Si bond, long Si–Cl bonds, and short contacts between the hydrides and silicon atom. Along with these structural features, the conformation of the silyl ligand around the W–Si bond may suggest the presence of a double interligand hypervalent interaction between the dichlorosilyl and hydrides ligands.

1,5,3,7-Dithiadiazocanes, 1,5,3,7-diselenadiazocanes, and 1,5,3,7-ditelluradiazocanes were prepared from a primary amine, formalin, and H 2 S, NaSeH, or NaTeH, respectively. Oxidation of 1,5,3,7-diselenadiazocanes and 1,5,3,7-ditelluradiazocanes using NBS efficiently afforded 1,2,4-diselenazolidines or 1,2,4-ditellurazolidines, respectively. In contrast, treatment of 1,5,3,7-dithiadiazocanes with bromine-elemental sulfur or disulfur dichloride (S 2 Cl 2 ) afforded 1,2,3,4,5,7-pentathiazocanes. An unusual oxidative conversion of 1,5,3,7-dichalcogenadiazocanes into these products was assumed to proceed through in situ formation of l,5,3,7-dichalcogenadiazabicyclo[3.3.0]octane-type dications.

Dihydride silyl complexes Cp*(CO)2W(H)2(SiHPhR) (R = Ph, 7; H, 8) were synthesized by treating the donor-stabilized silylene complexes cis-Cp*(CO)2(H)WSiRPh·Do (R = Ph, H; Do = Py, THF) with LiAlH4 to give Li[Cp*(CO)2W(H)(SiHPhR)] (R = Ph, 5; H, 6) followed by protonation using CF3COOH. X-ray analyses of the crystals of 7 and 8 revealed that the former adopts a distorted pseudo-octahedral structure (7a), while the latter possesses a pseudo-trigonal-prismatic structure (8b). In solution, both complexes exist as equilibrium mixtures of these two structural isomers: the distorted pseudo-octahedral isomer (7a/8a) and the pseudo-trigonal-prismatic isomer (7b/8b). In addition to this interconversion process, two dynamic processes involving site exchanges of hydride and silyl ligands in the pseudo-trigonal-prismatic isomer were shown for 8b by detailed NMR studies. The addition of HCl to cis-Cp*(CO)2(H)WSiHPh·THF afforded Cp*(CO)2W(H)2(SiHPhCl) (9), which also gave an equilibrium mixture of the distorted pseudo...

A stereocontrolled synthesis of the IJK ring segment of yessotoxin is described. Cyclization of 11 mediated by SmI2 gave the IJ ring system 12 as the sole product. Construction of the K ring moiety was performed by the acid catalyzed cyclization of epoxy alcohol 20 to afford the IJK ring segment in a highly stereocontrolled manner.

The precise X-ray structures of furo[3,4-d]tropone (2), 2,4-dimethyl-8H-3-oxaheptalen-8-one (5), and 4,5-benzotropone (6) were determined. Their tropone rings show definite bond alternation and nea...

A photoinduced electron-transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone ( 1 ) in benzene gave two unexpected CA-adducts, 5,5-dianisyl-4,4-dimethyl-3-[1-(4-hydroxy-2,3,5,6-tetrachlorophenyl)methylethylidene]dihydrofuran-2-one ( 7 ) and 2,2-dianisyl-4-(4-hydroxy-2,3,5,6-tetrachlorophenoxy)-4-isopropenyl-3,3-dimethylcyclobutanone ( 8 ), while the reaction in acetonitrile did not, suggesting significant solvent effects on the product distribution.

[structure: see text] This paper describes the cyclotrimerization reaction of di(2-azulenyl)acetylenes (2a,b) catalyzed by Co2(CO)8 to produce hexa(2-azulenyl)benzene derivatives (1a,b). The cyclooligomerization of 2a and 2b utilizing CpCo(CO)2 as a catalyst produced (eta5-cyclopentadienyl)[tetra(2-azulenyl)cyclobutadiene]cobalt complexes (3a,b). The redox behavior of hexakis(6-octyl-2-azulenyl)benzene (1b), bis(6-octyl-2-azulenyl)acetylene (2b), and the cobalt complexes 3a and 3b along with 6-octyl-2-phenylazulene (19) was examined by cyclic voltammetry (CV). The reduction of compound 1b exhibited multiple-electron transfers in one step upon CV with a reduction potential similar to that of compound 19. However, the CVs of compounds 2b, 3a, and 3b were characterized by stepwise waves because of the reduction of each azulene ring. The mesomorphic behaviors of 1b, 2b, and 19 were also studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques. A new series of azulene derivatives, 1b, 2b, and 19, substituted by a long alkyl chain at the 6-position shows mesomorphism with crystalline polymorphs. Compound 1b showed a large temperature range of hexagonal columnar mesophases (Col(ho)) from 115.5 to 199.9 degrees C. Compound 2b has rectangular columnar (Col(ro)), smectic E (S(E)), and nematic (N) mesophases. Compound 19 exhibited an S(E) mesophase.

A photoinduced electron-transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone ( 5 ) in acetonitrile containing molecular oxygen or water gave 4,4′-dimethoxybenzophenone ( 7 ) and 2,2-dianisyl-4-isopropylidene-5,5-dimethylhydrofuran-3-one ( 8 ), demonstrating the chemical capture of an unprecedented oxatetramethyleneethane-type radical cation intermediate ( 6 + ). A density functional theory calculation suggests through-space electronic coupling between the tetramethylallyl and joined dianisylmethyl carbonyl subunits in 6 + .

Inherently chiral anti-O,O′-dibenzyl-p-tert-butylcalix[4]arene 1 was resolved as the (S)-2-methoxy-2-(naphthalen-1-yl)propionic ester by flash chromatography. Conversely, the anti-O,O′-dibutyl analogue 2 was resolved as the (Sa)-2′-methoxy-1,1′-binaphthalene-2-carboxylic ester by crystallization combined with flash chromatography. CD analysis of these compounds indicated the absolute stereochemistries to be (Sa)-(+)-1 and (Sa)-(+)-2, respectively, the former of which was confirmed by X-ray crystallographic analysis.

Enantiomeric discrimination of chiral secondary alcohols was performed by both reversed-phase HPLC and 1H-NMR after labeling with a chiral fluorescent derivatization reagent, 2-(2,3-anthracenedicarboximide)cyclohexanecarboxylic acid. It was possible to discriminate by HPLC the chirality of alcohols up to C30 having a chiral hydroxyl group at the middle of the straight alkyl chain, and, by 1H-NMR, alcohols up to C16. For alcohols having one straight alkyl and one isoalkyl group with the same carbon numbers at both sides of a hydroxyl group, it was possible to discriminate the chiralities of alcohols up to C19 by both 1H-NMR and HPLC. The 1H-NMR methods also made it possible to determine absolute configurations empirically. Chirality 17:S171–S176, 2005. © 2005 Wiley-Liss, Inc.

We successfully synthesized silicon- and germanium-based allenes as isolable crystalline compounds. These allenes were found to have bent and fluxional structure in sharp contrast to carbon allenes having rigid linear structure. Remarkable red-shifts of the absorption bands of these allenes indicate the significant interactions between two cumulative double bonds.

Cationic palladium (Pd)- and platinum (Pt)-phosphinooxazolidine catalysts 13a-c, 15a-d, 17a-c, and 19a-c were prepared from phosphinooxazolidine ligands 1-3, MCl(2) (M = Pd and Pt), and counterions, and the activities of the catalysts in the asymmetric Diels-Alder (DA) reactions of cyclic or acyclic dienes with imide dienophiles were investigated. These catalysts demonstrated high levels of catalytic activity. The cationic Pd-POZ complex 13c provided particularly excellent enantioselectivity (98% ee) in the DA reactions of cyclopentadiene with acryloyl-, crotonyl-, and fumaroyl-1,3-oxazolidin-2-ones (20a-c).

Treatment of readily available O,O′-1,1,3,3-tetraisopropyldisiloxane-1,3-diyl-bridged p-tert-butylthiacalix[4]arene ( 1 ) with tri(ethylene glycol) di-p-tosylate and subsequent desilylation gave O,O′-bridged thiacalix[4]crown 3 in an excellent yield. Mono-O-alkylation of 3 with ethyl bromoacetate, followed by optical resolution by chiral HPLC, and subsequent hydrolysis of the ester moiety gave inherently chiral O,O′-bridged thiacalix[4]crowncarboxylic acid (+)-6 , which clearly discriminated enantiomeric primary amines, as well as amino esters, by 1H NMR spectroscopy.

The reactions of isolable dialkylgermylene and -stannylene with a galvinoxyl radical were found to give rather unusual cyclic compounds in high yields via intermediate adduct radicals. The structures of the cyclic compounds were determined by X-ray crystallography. We propose a concerted cyclization mechanism in which the abstraction of a hydrogen atom from the tert-butyl group by the galvinoxyl radical is accompanied by the simultaneous attack of the germyl radical center to the tert-butyl carbon atom.

The results of the thermolysis of 1:2 adducts of stable group-14 element divalent compounds [R2M:, R2=1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl; 1b, M=Ge; 1c, M=Sn] to TEMPO radical are discussed in detail. Whereas the thermal reactions of the 1:2 adducts [R2M(OR′)2, R′=2,2,6,6-tetramethylpiperidin-N-yl; 3b, M=Ge; 3c, M=Sn] are understood to proceed by the initial homolysis of an M–O bond to give the corresponding aminoxy-substituted group-14 element radicals [R2(R′O)M ; 2b, M=Ge; 2c, M=Sn] and TEMPO, the subsequent reactions of 2b and 2c were remarkably different to each other; 2b favors the N–O bond fission (path b) to give the corresponding germanone, while 2c prefers the M–O bond fission (path a) to give stannylene (1c). In combining with our previous results for aminoxysilyl radical (2a) [R2(R′O)Si ], the origin of the remarkable differences in the reactivity among group-14 element radicals 2a–2c is discussed on the basis of the theoretical calculations for model reactions. Improved syntheses of the precursor dichlorogermane and dichlorostannane of germylene (1b) and stannylene (1c), respectively, are described in Section 3 .

Development of a new, efficient resolution method of α-cyano-α-fluoro- p -tolylacetic acid (CFTA) 2a has been successfully achieved, which has been troublesome to obtain by conventional methods, in spite of its outstanding ability as an NMR chiral derivatizing agent. Fractional recrystallization of a mixture of the diastereomeric CFTA esters prepared from racemic CFTA chloride and (1 R ,2 S )- N -carbobenzyloxy- cis -1-amino-2-indanol (−)- B afforded the less-soluble diastereomer, which was hydrolyzed to give ( S )- 2a . It has also been demonstrated that optically active N -acetyl- cis -1-amino-2-indanol is effective for the chromatographic resolution of α-arylacetic acids including ibuprofen and naproxen.

5H-1,2,4-oxathiazoles were efficiently synthesized from 6H-1,3,5-oxathiazine S-oxides by thermal cycloreversion of the substrates and the products were effectively converted into 1,2,4-thiadiazoles. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:175–186, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20004

Inclusion abilities of water-soluble thiacalix[4]arenetetrasulfonate (3) and mono-O-carboxymethylated derivatives 5 and 6 toward water-miscible organic molecules such as alcohols, ketones, and nitriles in water were investigated by 1H NMR. The limit chemical shift change of the guest upon inclusion in the host suggested that the hosts regioselectively encapsulate the guests from the side of aliphatic moiety. Large guests such as pentan-1-ol showed folding of the alkyl chain to be included inside the cavity. On the other hand, mono-O-substituted 6 included a guest molecule less deep in the cavity than 3 did. Binding constants (K) of 3 toward guest molecules increased with hydrophobicity of the guest, suggesting that hydrophobic effect plays a main role for the complexation. On the contrary, mono-O-carboxymethyl derivatives 5 and 6 showed the opposite dependency of stability on hydrophobicity; higher affinities toward less hydrophobic guests. Among the guests examined, the smallest entities such as CH3OH and CH3CN were best included in 5 with the highest binding constant ever reported (K > 102 M-1). It was concluded that introduction of the carboxymethyl group into one of the phenolic OH of thiacalix[4]arene led to tuning of the cavity shape for stereospecific inclusion of small guests. The tuning of cavity by the O-alkylation was actually confirmed by X-ray crystal analysis of a complex of 5 with diethyl ketone.

Two novel A2SiSiB2-type tetrakis(trialkylsilyl)disilenes: 3(A=t-BuMe2Si, B=i-Pr2MeSi) and 4 (A=t-BuMe2Si, B=i-Pr3Si) were synthesized in good yields. X-ray structural analysis revealed that both 3 and 4 have a twisted SiSi double bond with a planar arrangement around each of the unsaturated silicon atoms. The twist angle around the SiSi double bond is remarkably dependent on the substituents and amounts to 27.95(3)° for highly congested disilene 4. Disilene 3 underwent gradually a formal dyotropic rearrangement of trialkylsilyl substituents to give an equilibrium mixture of 3 and (E)- and (Z)-isomers of the corresponding ABSiSiAB-type disilenes (2E and 2Z). The activation energy for the isomerization of 3 to 2Z and/or 2E was found to be much smaller than that for the corresponding isomerization of a tetraaryldisilene system.

The first η2-disilene–palladium complexes were synthesized using two different reactions; the reactions of bis(phosphine)dichloropalladiums with a 1,2-dilithiotetrakis(trialkylsilyl)disilane, which was prepared by the reaction of a stable tetrakis(trialkylsilyl)disilene with lithium (Method A) and the direct reactions of the bis(phosphine)dichloropalladiums with the stable disilene (Method B). Comparison of X-ray structural parameters of the disilene–palladium complexes with those of the corresponding platinum complex has indicated that the palladium complex is a metallacycle but its π-complex character is stronger than that of the platinum complex.Key words: disilene complex, palladium, platinum, X-ray structure, metallacycle, π-complex.

Preparation and cycloaddition reaction of novel azulene-substituted N-sulfinylamines 1 and 2 are reported. The influence of the –NSO group on the UV–vis and NMR spectra of the azulene ring to which it is bonded is discussed. X-ray crystal analysis of 1 revealed the syn-configuration and the twisted structure of the N-sulfinylamine moiety. The synthetic utility of 1 and 2 have been explored by the cycloaddition reaction to afford novel azulene-substituted heterocycles under high-pressure conditions. We also described herein the synthesis and some properties of related 2-azulenylisothiocyanate.

All six stereoisomers of dimethyl 5,5′-dihydroxy-1,1′,12,12′-tetramethyl-[6,6′]bi(benzo[c]phenanthrenyl)-8,8′-dicarboxylate (bihelicenol) were synthesized by the oxidative coupling of methyl 8-hydroxy-1,12-dimethylbenzo[c]phenanthrene-5-carboxylate (helicenol), and their structures were determined by X-ray analysis.

All four stereoisomers of p-tert-butylsulfinylcalix[4]arene [4(rccc), 4(rcct), 4(rctt), and 4(rtct)], arising from the disposition of the four sulfinyl groups with respect to the mean plane of the four bridging sulfur atoms, have been prepared via oxidation of p-tert-butylthiacalix[4]arene (2) or its tetra-O-benzyl ethers 5 of defined conformations. Thus, treatment of 2 with 4.4 molar equiv of NaBO3·4H2O gave the rtct and rctt isomers in 27% and 17% yields, respectively, while oxidation of cone 5 (5C) and partial cone 5 (5PC) proceeded stereoselectively to give, after debenzylation of the resulting tetrasulfoxides 12 and 15, the rccc and rcct isomers in 56% and 28% yields, respectively, based on 5. The sulfinylcalix[4]arenes 4 were treated with iodomethane in the presence of a base to give the corresponding tetramethyl ethers 16, the structures of which in regard to the disposition of the sulfinyl groups and the conformation of the phenol units were determined by X-ray crystallography. Also reported is th...

The Pd(II) complexes of thiacalix[4]aniline (TCAn) and thiacalix[4]arene (TCAr), in which four aniline and phenol units are linked by four sulfides at the o,o′-positions, respectively, were prepared by simply heating the ligands with Pd(II)(OAc)2 in CHCl3 or benzene at reflux and structurally characterized by X-ray diffraction methods. In TCAn, two thiacalix ligands adopting a pinched-cone conformation are fused at the narrower rims to coordinate to two Pd(II) ions by amide NH− and the adjacent S atoms. In contrast for TCAr, two ligands coordinate to two Pd(II) ions with phenolate O− and thioether S atoms at the narrower rims. Four sets of hydrogen bonding between the O− and free OH cause a deviation of the Pd(II) centers from the square coordination plane and also lead the conformation of the calix to be more cone-like to provide enough space to accommodate guest CH3CN molecules.

The reactions of a stable dialkylsilylene with chlorosilanes such as tetrachlorosilane, dimethyldichlorosilane, and dichlorosilane occurred smoothly at room temperature in hydrocarbon solvents to give the corresponding Si-Cl bond insertion products. In the reaction of the silylene with dichlorosilane, only the Si-Cl bond insertion product was obtained, while a similar reaction with dimethylchlorosilane gave only the Si-H insertion product, emphasizing the remarkable difference in the steric requirements between these two insertion reactions. No reaction took place during the treatment of the silylene with trimethylchlorosilane. The Si-Cl insertion reactions are expected to be applied in the synthesis of new organosilicon frameworks that cannot be obtained by conventional methods.

We synthesized 5-chloro- and 5-bromo-substituted 2-(pentamethyldisilanyl)-1,4-benzoquinones 1a and 1b, respectively. Their electronic absorption spectra showed significant intramolecular charge-transfer interaction between disilane and 1,4-benzoquinone moieties. The intramolecular σ(SiSi)–π* transition energies of 1a and 1b were lower than that of 2-(pentamethyldisilanyl)-5-t-butyl-1,4-benzoquinone (1c). X-ray crystallographic analysis of chloro-substituted derivative 1a revealed that the angle between the Si–Si bond and the quinone ring was 74° and also that the structure of 1a in the solid state was also advantageous for CT interaction. Photoreaction of 1a and 1b gave α-sila-m-quinonemethide derivatives 3a and 3b, respectively, which were trapped by acetone. Matrix isolation of 3a, 3b, and their 2-methyltetrahydrofuran-complexes were accomplished in glass matrixes.

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.

Syn and anti isomers of a novel saturated sila-macrobicyclic compound, hexasilabicyclo[12.8.8]triacontane, were synthesized via the functionalization of 1,1,10,10-tetraphenylhexasilacyclooctadecane derivative, which was obtained by the diimide hydrogenation of the corresponding hexasilacyclooctadecahexayne derivative. The structures of these macrocyclic compounds were determined by 1H, 13C, and29Si NMR and X-ray crystallography.

Chiral cationic palladium[bond]phosphinooxathiane complexes have been found to be effective catalysts for enantioselective Diels-Alder (DA) reaction of cyclopentadiene with acyl-1,3-oxazolidin-2-ones to give the corresponding DA adducts in good yield and high enantioselectivity up to 93% ee.

Diastereomeric triamines containing two helicene moieties, 1,12-dimethylbenzo[c]phenanthrene, were synthesized and found to form folded structures in the water. Such folding was not observed for an achiral compound possessing a naphthalene moiety. The (M,M)-dihelicenetriamine with matching configuration at the helicene moieties formed a more stable folded structure than the (P,M)-isomer containing two enantiomeric helicene groups. The most stable folded conformation was predicted by the Monte Carlo method with Amber force field of the dihelicenetriamine.

Hexakis(trialkylsilyl)cyclotrisilanes 1a (trialkylsilyl = tert-butyldimethylsilyl) and 1b (trialkylsilyl = diisopropylmethylsilyl) were synthesized by the reductive coupling of the corresponding 2,2-dibromotrisilanes. Their molecular structures were confirmed by X-ray crystallography. In the absence of trapping reagents, photolysis of cyclotrisilanes 1a and 1b gave the corresponding stable tetrakis(trialkylsilyl)disilenes quantitatively. Irradiation of cyclotrisilanes 1a and 1b in (Z)-2-butene and (E)-2-butene afforded exclusively the corresponding (Z)- and (E)-2,3-dimethyl-1-silacyclopropanes, respectively. Stereospecific formation of the cycloadducts indicates that the bis(trialkylsilyl)silylenes generated from cyclotrisilanes 1a and 1b would be singlets in the ground state.

X-Ray crystal structures of the mono-, di-, and tri(p-tert-butyl)-substituted thiacalix[4]arenes (TC4As; 1, 2, and 3, respectively) have beendetermined. TC4As 1–3 adopt a cone conformation and form dimeric self-inclusion units in such a manner that phenol moieties are inserted into the cavity of each molecule. In all the crystal structures of 1–3, lateralface-to-face interactions exist between the phenol rings that do not bear a tert-butyl substituent, and seemingly, this molecular assembly stabilizes the formation of self-inclusion. TC4As 1 and 2 adopt a cone conformation with C2 symmetry, leading to the formation of rim-to-rim intermolecular hydrogenbonds so as to link the dimeric units up and down. On the other hand, 3 adopts a regular cone conformation with C4 symmetry to form cyclic hydrogen bonds withinthe rim part of TC4A.