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Some 5H,7H-dibenzo[b,g][1,5]dithiocin oxides (4–8) and their related compounds 9–13 were prepared and the assignment of the most favorable conformation was carried out on the basis of the characteristic 1H NMR spectral data. Only a single conformer (BC: boatchair form) exists for 4,5, and 8–13, while two conformers (BC and TB: twist-boat form) are apparent for 6 and 7. Oxidation and methylation of 4 gave exclusively a single geometrical isomer (8 and 13, respectively). These results are interpreted as a sterically preferential attack of electrophiles on the BC conformer of the starting material. A 1,5-oxygen shift of 4 occurred smoothly to give 6 in the presence of trifluoroacetic acid in CDCl3 solution. The mechanistic investigation is described briefly. Differences in chemical behavior between dibenzodithiocin 12-oxide 4 and dibenzothiazocine 12-oxide 2 are also discussed on the basis of the conformational features.

A series of 10-S-3 type sulfuranes, tetraazathiapentalenes (10a-i, 11a-f, 12, and 17) fused with pyrimidine ring and/or pyridine ring, were prepared by oxidation of the corresponding thioureas. The restricted internal rotation of the pyrimidine ring was observed by temperature dependent 1H NMR spectrum which gave the kinetic parameters of ΔG298_??_=16.6kcal/mol, ΔH=15.9kcal/mol, and ΔS_??_=-2.4 eu at 25°C for the rotational barrier in 10a. The substituent effect to the kinetic data can be reasonably explained in terms of electronic balance of the N-S-N hypervalent bond or the different degree of contribution of resonance canonical structures. Comparison of the rotational barrier of 10a with that of model compounds (18 and 24) suggests that hypervalent N-S-N stabilization in 10a is more than 6kcal/mol. Methylation of these 10-S-3 type sulfuranes (10a, 10d, and 11a) was investigated to clarify the electronic effect in these molecules. The crystal structure of the neutral symmetric sulfurane 10a reveals to be a planar molecule in which the sulfur atom was found to be in the same plane of the two pyrimidine rings. The S-N bond lengths 1.948(3) and 1.938(3) A are longer than the sum of the covalent bond radii, consistent with a bond order less than unity. The crystal structures of the dicationic symmetric sulfurane 17 and the unsymmetrical sulfurane 11a also show to be planar molecules. The S-N distances in 11a were different each other due to the electronic imbalance between the apical ligands. Semi-empirical calculation (AM 1) of these systems (10a and 17) indicate the expected electronic features of the hypervalent molecules (10-S-3 sulfuranes) and the small contribution of π-overlapping in the N-S-N bonds.

A series of neutral (8−10), monomethylated (12−14), and dimethylated (17) 10-S-3 sulfuranes, derivatives of tetraazathiapentalenes fused with pyrimidine and/or pyridine ring, were prepared. These molecules are planar, and bond energies of the hypervalent N−S−N bond were evaluated by the temperature dependent restricted rotation of the pyrimidine ring caused by cleavage of one of the S−N bonds. The bond length is longer, and the energy is lower for the S−N bond fused with more electron-withdrawing heterocycles.

Te(C6H4-4-CF3)61a was obtained by the unique one-pot reaction of LiC6H4-4-CF3 with TeCl4. The Te atom resides in the highest oxidation state (TeVI) having six C Te bonds in 1a. Compound 1a is extremely thermally stable and not light sensitive unlike tetraorganotellurium compounds. The X-ray crystallographic analysis of 1a revealed a rare example of approximately Th molecular symmetry.

Novel cationic Lewis acids were generated by the addition of silver hexafluoroantimonate to titanium complexes 7 (TiCl4·(R,R)-1,2-diphenylethane-1,2-diol dialkyl ether) or 8 (TiCl3(OR)·(R,R)-1,2-diphenylethane-1,2-diol dialkyl ether) at −20 °C. Interestingly, the titanium complexes 7 or 8 could be isolated and the structures of 7c (TiCl4·(R,R)-1,2-diphenylethane-1,2-dioldi-n-propyl ether) and 8a (TiCl3(O-i-Pr)·(R,R)-1,2-diphenylethane-1,2-diol dimethyl ether) were determined by X-ray analysis. Asymmetric aldol reaction using the cationic Lewis acids is also described.

The synthesis of (S,S)-1,2-bis(3,5-di-tert-butylphenyl)ethane-1,2-diol (98.6% ee), which should be useful as a chiral ligand of catalysts in asymmetric inductions, is described.

Te(C6H4-4-CF3)6 1a was obtained by the unique one-pot reaction of LiC6H4-4-CF3 with TeCl4, where oxidation of Te(IV) to Te(VI) occurred. Compound 1a is extremely thermally stable and not light sensitive unlike tetraorganotellurium compounds. Thermolysis and some reactions of 1a are described. ClTe(C6H4-4-CF3)5, synthesized by chlorination of LiTe(C6H4-4-CF3)5, reacted with LiC6H4-4-CF3 to give 1a. Bond dissociation energies of Te(CH3)n (n = 2, 4, 6) were calculated in order to explain the stability of Te(VI) compounds.

[(Por)M(R)(OOR′)]+Y− (Por: TPP [tetraphenylporphyrin], OEP [octaethylporphyrin]; M: Sb, As, P; R: Me, Et, Ph; R′: H, C(=O)m-ClC6H4, t-Bu) were prepared from [(Por)M(R)(X)]+Y− (X: OTf, Br). The reactivities of the peroxide porphyrins toward nucleophiles such as triphenylphosphine increased in the order of -OOt-Bu, m-CPBA, and -OOH derivatives. Phosphorus (P-OOH) and arsenic hydroperoxide (As-OOH) were much more reactive than the corresponding antimony hydroperoxide (Sb-OOH). The higher reactivity of phosphorus and arsenic peroxides can be explained by the stability of the M=O (M=P, As) bonding system in the intermediates of the oxidation reactions. An X-ray structural analysis of [(TPP)Sb-(Me)(OOt-Bu)]+PF6− is presented. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:431–443, 2001

Hypervalent 10-Sn-5 allyl and crotyl tin ate complexes bearing Martin ligands were prepared and found to be surprisingly stable in water. These compounds were found to react with aldehydes in the presence of weak Lewis acids such as LiBr to give the corresponding homoallyl alcohols. Product analysis of the reaction of the crotyl compounds indicated that the reaction occurred via a cyclic transition state unlike an acyclic transition state operative for widely utilized allyltrialkyltin reagents that are of ordinary valency. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:425–430, 2001

Phosphoranes (10-P-5) bearing cyanomethyl, acetamide, and N,N-dimethylacetamide groups were examined for Wittig type reactions. All three reacted to give the corresponding olefins. The reaction of the cyanomethyl reagent with aldehydes gave α,β-unsaturated cyanides with high Z-selectivity in the case of aliphatic aldehydes (Z:E=94:6 to 99:1). On the other hand, the reactions of the two amide reagents with aldehydes yielded α,β-unsaturated amides with high Z-selectivity for both aromatic and aliphatic aldehydes (Z:E=99:1 to >99

The regioselective and stereospecific intramolecular ring closure reactions of o-ethynylbenzyl tellurols 5A and o-ethynylbenzyl selenols 5B, which were readily generated by the reaction of the o-ethynylbenzyl bromides 4 with sodium hydrogen telluride (NaHTe) or sodium hydrogen selenide (NaHSe), produced the isotellurochromenes 6A and isoselenochromenes 6B together with (Z)-1-methylidene-2-telluraindans 7A and (Z)-1-methylidene-2-selenaindans 7B, respectively. The obtained isochromenes 6A and 6B were transformed into the corresponding 2-benzotelluropyrylium tetrafluoroborates 9A and 2-benzoselenopyrylium tetrafluoroborates 9B by treatment with triphenylcarbenium tetrafluoroborate (Ph3C+BF4−) in excellent yields, respectively. An X-ray structural analysis of the tert-butyl derivatives 9Ac and 9Bc is also described.

The anionic 10-Bi-4 species ( 2a , 2b ) were synthesized by the reaction of BiCl 3 with 2 equiv of lithium 2-(2-lithiophenyl)-2-propoxide derivatives ( 1a , 1b ). The X-ray crystallographic analysis showed 2a- Et 4 N + to be distorted pseudotrigonal bipyramid in geometry. Reaction of dimethyl-substituted 2b- Li + with methyl iodide took place exclusively not at the bismuth but at the oxygen to give an ether 4 .

A 10-Sb-4 type organoantimony ate complex was prepared from hexafluorocumyl alcohol and SbCl3 as an air and water stable compound. Its X-ray structural analysis revealed a distorted pseudo-trigonal bipyamidal structure. The compound reacted with both alkyl halides and organolithium reagents to yield neutral 10-Sb-5 compounds.

Stable anionic 10-Sn-51) species, tetraalkylammonium bis[α,α-bis(trifluoromethyl)benzenemethanolato(2−)-C2,O]alkylstannates(1−) [2a (R = Ph), 2b (R = p-CH3C6H4), 2c (R = n-Bu), and 2d (R = Me)], were prepared. Reaction of 2a and 2b with sulfuryl chloride gave chlorostannate (3a), which could be converted to fluorostannate (3b). 3a and 3b reacted with organolithium reagents to give 2. The X-ray crystallographic analysis of 3b-n-Bu4N+ revealed a distorted trigonal bipyramidal structure.

The mechanism we propose for the cyclopentane annulation is the following one. The allylic reagent (5D) attacks the siloxypyrylium salts (2a,b) at the C2 position, giving the intermediate carbocation (B) which is stabilized by the trimethylsilyl and the methyl group. Attack by the emerging enolate at C 3 , forms the five-membered ring compound (8a,b). Generally, electrophiles attack allylic silanes anti to the silyl group. Since there is undoubtedly interaction with the silicon in the transition state, the stereochemistry of the bridged intermediate (B) should be trans geometry due to stereoelectronic effect and allylic 1,3-strain. In the reaction of 2a, the favored pathway is cyclization. However, competition between cyclization and desilylation was observed in 2b due to steric hindrance between the two methyl groups at the step of cyclization

New title dibenzobicyclic stiboranes and related phosphoranes were prepared by means of tridentate 2,2′-diphenolamines. Coordination number of the central pnictogen atoms (Sb and P) changed from three into five during the reaction.

The reactions of allylstannanes with 4-siloxy-1-benzopyrylium salts gave the corresponding allylated derivatives more smoothly than allylsilanes. Similar reactions with 3-trimethylsilyl-1-butene afforded unexpected five-membered ring adducts in 87% and 37% yields, respectively.

In the presence of metallic bismuth, bismuth(III) chloride–metallic zinc, or bismuth(III) chloride–metallic iron, allylic halides have been found to react with aldehydes under mild conditions to give the corresponding homoallylic alcohols in high yields with high chemo-, regio-, and stereoselectivity. Allylic halides have been also found to react with aldehydes at room temperature in tetrahydrofuran–water by using bismuth(III) chloride–metallic aluminium to afford the expected homoallylic alcohols in high yields.

Symmetrical 10-S-3 sulfuranes ( 1a - c ) fused with two pyrimidine rings and their unsymmetrically substituted ones ( 1d , e ) were synthesized by oxidation of the corresponding thioureas. Substituent effect on the kinetic data of the restricted rotation was explained in terms of the balance of electron-withdrawing ability of the ligand in the NSN hypervalent bond.

The oxidized octaethyltetraphenylporphyrin (1, OETPP) and the corresponding newly prepared octaisobutyltetraphenylporphyrin (3, OisoBuTPP) could be isolated from the reaction of OETPPLi2 (or OisoBuTPPLi2) with SOCl2. The X-ray analysis and the characteristic UV-vis spectra of 1 and 3 revealed that these are the first examples of 16 pi nonaromatic porphyrins.

X-ray analysis of bis(p-fluorophenyl)methyl cation bearing a 2,6-bis(p-tolyloxymethyl)benzene ligand showed a symmetrical structure (10-C-5) where the two C-O distances are identical, although the distance (2.690(4) A) is longer than those (2.43(1) and 2.45(1) A) of 1,8-dimethoxy-9-dimethoxymethylanthracene monocation, which was recently reported by us. However, X-ray analysis of the more stable aromatic xanthylium cation with the same benzene ligand showed the tetracoordinate carbon structure where only one of the two oxygen ligands is coordinated with the central carbon atom. These results clearly indicate that the carbocations (10-C-5) bearing the sterically flexible benzene ligand were quite sensitive to the electronic effect on the central carbon atom. The electron distribution analysis by accurate X-ray measurements and the density functional calculation on the initially mentioned bis(p-fluorophenyl)methyl cation clearly show that the central carbon atom and the two oxygen atoms are bonded even if the bond is weak and ionic based on the small value of the electron density (rho(r)) and the small positive Laplacian value (nabla(2)rho(r)) at the bond critical points.

Pentacoordinate and tetracoordinate carbon and boron compounds (27, 38, 50-52, 56-61) bearing an anthracene skeleton with two oxygen or nitrogen atoms at the 1,8-positions were synthesized by the use of four newly synthesized tridentate ligand precursors. Several carbon and boron compounds were characterized by X-ray crystallographic analysis, showing that compounds 27, 56-59 bearing an oxygen-donating anthracene skeleton had a trigonal bipyramidal (TBP) pentacoordinate structure with relatively long apical distances (ca. 2.38-2.46 A). Despite the relatively long apical distances, DFT calculation of carbon species 27 and boron species 56 and experimental accurate X-ray electron density distribution analysis of 56 supported the existence of the apical hypervalent bond even though the nature of the hypervalent interaction between the central carbon (or boron) and the donating oxygen atom was relatively weak and ionic. On the other hand, X-ray analysis of compounds 50-52 bearing a nitrogen-donating anthracene skeleton showed unsymmetrical tetracoordinate carbon or boron atom with coordination by only one of the two nitrogen-donating groups. It is interesting to note that, with an oxygen-donating skeleton, the compound 61 having two chlorine atoms on the central boron atom showed a tetracoordinate structure, although the corresponding compound 60 with two fluorine atoms showed a pentacoordinate structure. The B-O distances (av 2.29 A) in 60 were relatively short in comparison with those (av 2.44 A) in 59 having two methoxy groups on the central boron atom, indicating that the B-O interaction became stronger due to the electron-withdrawing nature of the fluorine atoms.

We propose “superphenalenyl” as a novel π-conjugated planar hydrocarbon radical. Theoretical calculation was performed to evaluate its stability compared to phenalenyl and trioxotriangulene. The re...

Novel spirophosphoranes (O-cis) that exhibit reversed apicophilicity having an apical carbon-equatorial oxygen array in a five-membered ring showed enhanced reactivity toward nucleophiles such as n-Bu(4)N(+)F(-) or MeLi in comparison with the corresponding stable isomeric spirophosphoranes (O-trans) having an apical oxygen-equatorial carbon configuration. The enhanced reactivity of the O-cis isomer could be explained by the presence of a lower-lying sigma(P)(-)(O(equatorial)) orbital as the reacting orbital in the equatorial plane, whereas the corresponding orbital is a higher-lying sigma(P)(-)(C(equatorial)) in the O-trans isomer. Density functional theory (DFT) calculation on the actual compounds provided theoretical support for this assumption. In addition, we found that the benzylic anion alpha to the phosphorus atom in O-cis benzyl phosphorane is much more stable than that generated from the corresponding O-trans compounds. The experimental results were considered to be due to the n(C) --sigma(P)(-)(O) interaction in the O-cis anion, and this was confirmed by DFT calculations. Furthermore, the hexacoordinate anionic species derived from the reaction of the benzylic anion from O-cis benzylphosphorane with an aldehyde was also found to be stabilized as compared with analogous species from the corresponding O-trans isomer. The first X-ray structural characterization of a hexacoordinate phosphate intermediate in the Wittig type reaction using pentacoordinate phosphoranes is reported.

A variety of phosphorus(V) octaethylporphyrin derivatives of the type [P(OEP)(X)(Y)](+)Z(-) (OEP: octaethylporphyrin) (X = CH(3), CH(2)CH(3), C(6)H(5), F; Y = CH(3), CH(2)CH(3), OH, OCH(3), OCH(2)CH(3), On-Pr, Oi-Pr, Osec-Bu, NHBu, NEt(2), Cl, F, O(-); Z = ClO(4), PF(6)) were prepared. X-ray crystallographic analysis of eleven compounds reveals that the degree of ruffling of the porphyrin core becomes greater and the average P-N bond distance becomes shorter as the axial ligands become more electronegative. Therefore, the electronic effect of the axial substituents plays a major role in determining the degree of ruffling although the steric effect of the substituents plays some role. A comparison of the (1)H NMR chemical shifts for the series of [P(OEP)(CH(2)CH(3))(Y)](+)Z(-) complexes with those of the corresponding arsenic porphyrins, which possess a planar core, indicates a much smaller ring current effect of the porphyrin core in the severely ruffled phosphorus porphyrins. The electrochemistry, spectroelectrochemistry and ESR spectroscopy of the singly reduced compounds are also discussed. The OH protons of [P(OEP)(X)(OH)](+) are acidic enough to generate P(OEP)(X)(O) by treatment with aq dilute NaOH. X-ray analysis of P(OEP)(CH(2)CH(3))(O) reveals that the PO bond length is very short (1.475(7) A) and is comparable to that in triphenylphosphine oxide (1.483 A). The features of the quite unique hexacoordinate hypervalent compounds are investigated by density functional calculation of a model (Por)P(CH(2)CH(3))(O) and (Por)P(F)(O) (Por: unsubstituted porphyrin).

A variety of Group 15 element porphyrins bearing element–carbon bond(s) were synthesized mainly by use of R 3 Al as an alkylating reagent. The synthetic methods, X-ray crystallographic structures, some spectral data ( 1 H-NMR), and some reactions of the porphyrins were surveyed. One of the most important properties of these compounds is the formation of the element–oxygen double bond in the phosphorus and arsenic porphyrins. The bond formation was confirmed by X-ray crystallographic analysis of (OEP)P(Et)(O). The PO bond length of [(OEP)P(Et)(OH)] + Cl − and (OEP)P(Et)(O) was 1.636(4) and 1.484(9) A, respectively (cf. PO bond length of Ph 3 PO is 1.483 A). Since (OEP)P(Et)(O) was stabilized by the formation of the PO bond, the OH proton of [(OEP)PEt(OH)] + Cl − was acidic (p K a ca. 7–8). Although the similar formation of the double bond was not observed in the corresponding antimony compounds, the corresponding AsO formation was observed in newly synthesized (OEP)As(R)(O). The relatively high acidity of the OH protons in [(OEP)M(R)(OH)] + X − (M=P, As) {and the stability of the (OEP)M(R)(O)} would be the main reason for the relatively high reactivity of phosphorus and arsenic porphyrins, [(OEP)M(R)(OH)] + X − , toward (OEP)Al(Me) to give μ-oxobridged dinuclear porphyrins and the high reactivity of phosphorus and arsenic porphyrins bearing a OOH group toward triphenylphosphine. In addition, X-ray analysis of a variety of phosphorus(V), arsenic(V), antimony(V) octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP) derivatives showed the effect of the axial ligand(s) on the distortion of the porphyrin core from the plane.

In an exploration of six coordination and hypervalence in carbon compounds, steric constraints have been employed to bring four ether O atoms in close proximity to an allenic carbon atom. The dimethylated dication 2 is confirmed to have hexacoordinate carbon by experimental charge density analysis and DFT calculations and is arguably hypervalent. Copyright © 2008 American Chemical Society.

The energy of a 10–S–3 hypervalent, i.e., N–S–N, bond was theoretically determined to be 60.6 kcal/mol using bond energy density analysis with the density functional theory. Upon rotation of the py...

The oxidized octaethyltetraphenylporphyrin (1, OETPP) and the corresponding newly prepared octaisobutyltetraphenylporphyrin (3, OisoBuTPP) could be isolated from the reaction of OETPPLi2 (or OisoBuTPPLi2) with SOCl2. The X-ray analysis and the characteristic UV-vis spectra of 1 and 3 revealed that these are the first examples of 16 pi nonaromatic porphyrins.

A novel chlorogermylene compound, (1,8-dimethoxy-9-anthracenyl)chlorogermylene, has been synthesized by the reaction of GeCl2·dioxane and 9-lithio-1,8-dimethoxyanthracene. X-ray crystallographic st...