Quantum chemical study of the structure of bicyclo[2.2.0]hex-1(4)-ene and its dimers

The RHF, B3LYP, and PBE0/6-311G** quantum chemical methods are used to determine the point symmetry group and the equilibrium structure of bicyclo[2.2.0]hex-1(4)-ene (I, D _2h ), its two stable dimers (tricyclo[4.2.2.2^2,5]dodeca-1.5-diene (II, D _2h ) and 2,5-dimethylenetricyclo[4.2.2.0^1,6]decane (III, C ₂)), and pentacyclo [4.2.2.2^2,5]dodecane (IV, D ₂) that is a hypothetical intermediate in the dimerization reaction of the molecules of I. The relation of total energies is obtained with regard to zero-point vibrations: E(III) < E(II) ≪ E(IV) ≪ 2E(I).     

Asymmetric ruthenium‐catalysed [2+2] cycloadditions between bicyclic alkenes and chiral aryl‐substituted acetylenic acyl camphorsultam alkynes

The regio‐ and absolute stereochemistry of (7S)‐N‐[4‐(3‐thienyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam tetrahydrofuran hemisolvate, C₂₄H₂₉NO₃S₂·0.5C₄H₈O, and (7S)‐N‐[4‐(4‐tolyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam, C₂₇H₃₃NO₃S, have been established. One contains a half‐occupancy tetrahydrofuran solvent molecule located on a twofold axis and the other contains two crystallographically unique molecules which are nearly identical. The extended structures of both complexes can be explained via weak C—H...O interactions, which link the molecules together into two‐dimensional sheets in the ab plane for the thienyl complex and ultimately into a three‐dimensional structure for the tolyl derivative. The stereochemistry of both structures confirms that [2+2] cycloadditions of bicyclic alkenes and alkynes catalysed by ruthenium are exclusively exo.     

Facial selectivity in addition reactions to the highly strained enone in tricyclo[5.2.1.0]deca-2(6),8-dienone and tricyclo[5.2.1.0]dec-2(6)-enone

Tricyclo[5.2.1.0^2,6]deca-2(6),8-dien-3-one contains a highly strained central double bond due to geometrical constraints imposed by the tricyclic skeleton which does not allow optimal sp² hybridization at the C₂ and C₆ bridgehead positions. Michael addition of various nucleophiles (alkoxides, cyanide, and malonate) under protic conditions resulted in an exclusive exo-facial selectivity. This preference can be explained by steric and electronic factors. Michael additions using lithium dialkylcuprates resulted in predominant formation of endo-products, but also some exo-products were obtained. These exo-products arising from endo-approach may be the result of coordination of the cuprate with both the enone moiety and the olefinic C₈-C₉ bond. Michael additions to tricyclo[5.2.1.0^2,6]dec-2(6)-en-3-one, which lacks this C₈-C₉ double bond showed exclusive exo-facial selectivity to give exo-products. Besides these additions were all considerably slower than those to tricyclo[5.2.1.0^2,6]deca-2(6),8-dien-3-one proving significant electronic participation of the C₈-C₉ double bond in reactions with this substrate.     

Tricyclo[4.2.2.22,5] dodecane and Tricyclo [4.2.2.12,5]undecane. Preliminary communication

A synthesis of tricyclo [4.2.2.2^2,5]dodecane ( 19 ), a novel tricyclic C₁₂H₂₀ compound, is described. The key intermediate ketone 13 was prepared either from the C₁₀-photodimer 1 of cyclopentadienone or the C₁₁-cycloaddition products 11 and 12 . 13 was also transformed to tricyclo [4.2.2.1^2,5]undecane ( 8 ).     

Nitrochlorination of methyl tricyclo[4.1.0.02,7]heptane-1-carboxylate and phenyl tricyclo[4.1.0.02,7]hept-1-yl sulfone

Treatment of methyl tricyclo[4.1.0.0^2,7]heptane-1-carboxylate and phenyl tricyclo[4.1.0.0^2,7]hept-1-yl sulfone with a ～1:8 mixture of N₂O₄ and NOCl in diethyl ether at ?5 to 0°C gave products of formal anti-addition of NO₂Cl at the central C¹-C⁷ bond. In the reaction with phenyl tricyclo[4.1.0.0^2,7]hept-1-yl sulfone nitryl chloride acts as an effective chlorinating agent; as a result, a mixture of diastereoisomeric syn- and anti-6,7-dichlorobicyclo[3.1.1]hept-6-yl phenyl sulfones at a ratio of 7.5:1 is formed.     

The Novel Adamantane Isomer 2,5-Trimethylenenorbornane (Tricycio-[5.3.0.3,9]decane, 4-Homotwistbrendane)

A synthesis of the novel C₁₀H₁₆ hydrocarbon 2,5-trimethylenenorbornane (tricyclo[5.3.0.0^3,9]decane, 1 ), one of the 19 members of the ‘adamantaneland’, and its Lewis-acid-catalyzed rearrangement is described.     

Synthesis of diesters by addition of saturated carboxylic acids to tricyclodecenyl formate

Reaction of addition of C₁-C₅-saturated monobasic acids to tricyclo[5.2.1.0^2.6]dec-3-en-8(9)-yl for-mate in the presence of a catalyst, boron trifluoride etherate (BF₃·OEt₂), was used to synthesize homo- and mixed tricyclo[5.2.1.0^2.6]decane-3(4),8(9)-diol diesters. The synthesized formic-acetic and formic-propionic acid diesters have a pleasant odor and can be used as components for preparation of perfume formulations.     

Reactions of 1-halocycloheptenes with potassium t-Butoxide and with sodium pyrrolidide

Reactions of 1-halocycloheptenes with KO-t-Bu in DMSO and THF were studied. The principal products obtained could be accounted for on the basis of two competing dehydrohalogenation mechanisms. These are: dehydrohalogenation across the C₁-C₂ bond to give cycloheptyne; and dehydrohalogenation across the C₁-C₇ bond to give 1,2-cycloheptadiene. One or both of these intermediates react with KO-t-Bu to give 1-t-butoxycycloheptene in poor yield. The principal product from the three 1-halocycloheptenes in both solvents is tricyclo[7.5.0.0²8]tetradeca-2,14-diene (4), the dimer of 1,2-cycloheptadiene. Also formed are 5, the 2(8), 14-diene isomer of 4, presumably by cycloaddition of 1,2-cycloheptadiene and cycloheptyne, and 6, the 2,13-diene isomer of 4, by rearrangement of 4 effected by KO-t-Bu.Also studied were rections of 1 chloro- and 1-iodocycloheptene with sodium pyrrolidide (Na- NC₄H₈) in THF. These reactions give 1-(1-pyrrolidino)cycloheptene in fair yield together with smaller amounts of the 14-carbon hydrocarbons. Reactions of 1-chlorocycloheptene-1-¹⁴C and 4-chloro- and 4-iodobicyclo[5.1.0]oct-3-ene leading to (1-pyrrolidino)cycloheptenes were found to occur via both the corresponding cycloheptyne and 1,2-cycloheptadiene.     

Peri-selective photocycloadditions of methyl 2-pyrone-5-carboxylate with unsaturated cyclic ethers

Photosensitized cycloaddition reaction of methyl 2-pyrone-5-carboxylate ( 1 ) with 2,3-dihydrofuran gave cis- exo- and cis-endo-[2 + 2] cycloadducts across the C₃-C₄ double bond in 1 , and a [4 + 2] cycloadduct which was different in addition-orientation from the Diels-Alder adducts. Each [2 + 2] cycloadduct was obtained by the use of sensitizers having different triplet energies. Photosensitized reactions of 1 with 3,4-dihydro-2H-pyrans afforded cis-endo-[2 + 2] cycloadducts, respectively. The photocycloaddition mechanism was also explained from the excited state of 1 calculated by means of MNDO-Cl method.     

Adducts of Tricyclo[4.1.0.0<Superscript>2,7</Superscript>]heptane hydrocarbons with methane- and Halomethanesulfonyl Thiocyanates and their transformations in the presence of bases (nucleophiles)

1-R-Tricyclo[4.1.0.0^2,7]heptanes (R = H, Me, Ph) take up methane- and halomethanesulfonyl thiocyanates XCH₂SO₂SCN (X = H, Cl, Br) at the central C¹–C⁷ bond in benzene at 20°C with high anti-selectivity to give bicyclo[3.1.1]heptane derivatives with the 7-endo-oriented sulfonyl group and the thiocyanato group in the geminal position with respect to the R substituent. The syn-adducts lose HSCN molecule by the action of potassium tert-butoxide in THF at 0°C or on heating in boiling aqueous dioxane containing NaOH with formation of 1-(X-methylsulfonyl)tricyclo[4.1.0.0^2,7]heptanes. Under analogous conditions the anti-adducts (X = Me) are converted into 1,2-bis(7-syn-methylsulfonyl-6-endo-R-bicyclo[3.1.1]hept-6-exo-yl)disulfanes. The anti-adduct derived from unsubstituted tricyclo[4.1.0.0^2,7]heptane and MeSO₂SCN reacted with methyllithium or phenylmagnesium bromide to produce 7-anti-methyl(phenyl)sulfanyl-6-endo-methylsulfonylbicyclo-[3.1.1]heptanes which were also obtained by photochemical addition of MeSO₂SMe(or Ph) to tricyclo-[4.1.0.0^2,7]heptane. Geometric parameters of radical intermediates in the sulfonylation of 1-R-tricyclo-[4.1.0.0^2,7]heptanes were optimized ab initio using 6-31G basis set.     

`0'‐ and `8'‐shaped complexes generated from a nano‐sized oxadiazole‐containing organic ligand with CdI2 and CuI

A new nano‐sized rigid double‐armed oxadiazole‐bridged organic ligand, 2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl)ethenyl]phenyl}‐1,3,4‐oxadiazole, C₃₀H₂₀N₄O, L or (I), which adopts a cis conformation in the solid state, has been synthesized and used to create the two novel metallocycle complexes (2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)diiodidocadmium(II) dichloromethane monosolvate, [CdI₂(C₃₀H₂₀N₄O)]·CH₂Cl₂, (II), and di‐μ‐iodido‐bis[(2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)copper(I)], [Cu₂I₂(C₃₀H₂₀N₄O)₂], (III). Molecules of complex (II) adopts a 20‐membered `0'‐shaped metallocycle structure with crystallographic mirror symmetry. The discrete units are linked into one‐dimensional chains through intermolecular π–π and C—H...π interactions. In (III), the two I atoms and two Cu<sup>I</sup> atoms form a {Cu<sub>2</sub>(μ‐I)<sub>2</sub>} cluster. One {Cu<sub>2</sub>(μ‐I)<sub>2</sub>} cluster and two L ligands form two 20‐membered monometallic rings in a head‐to‐head fashion, leading to a discrete centrosymmetric `8'‐shaped metallocyclic complex. These metallocycles stack together via two kinds of intermolecular π–π interactions to generate a two‐dimensional network in the ac plane. The luminescence properties of (I)–(III) were investigated in the solid state at room temperature and displayed an obvious red shift.     

Effect of substituents on addition polymerization of norbornene derivatives with two Me3Si-groups using Ni(II)/MAO catalyst

Addition polymerization and copolymerization of bis(Me₃Si)-substituted norbornene-type monomers such as 5,5-bis(trimethylsilyl)norbornene-2, 2,3-bis(trimethylsilyl)norbornadiene-2,5 and 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7, in the presence of Ni(II) naphtenate/MAO catalyst were studied. Disubstituted norbornene and norbornadiene were found to be practically inactive in homopolymerization. On the other hand, their copolymerization with norbornene proceeded with moderate yields of copolymers containing predominantly norbornene units. Under studied reaction conditions 2,3-bis(trimethylsilyl)norbornadiene-2,5 was transformed into the only exo-trans-exo-dimer as a result of the [2+2]-cyclodimerization reaction. Moving Me₃Si-substituents one carbon atom away from norbornene double bond made 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7 active in homopolymerization and allowed to obtain addition homo-polymer with two Me₃Si-substituents in each elementary unit. The reaction mechanism and steric effect of Me₃Si-substituents are also discussed.     

A New Conformation With an Extraordinarily Long, 3.04 Å Two‐Electron,Six‐Center Bond Observed for the π‐[TCNE]22− Dimer in [NMe4]2[TCNE]2 (TCNE=Tetracyanoethylene)

[NMe₄]₂[TCNE]₂ (TCNE=tetracyanoethenide) formed from the reaction of TCNE and (NMe₄)CN in MeCN has ν_CN IR absorptions at 2195, 2191, 2172, and 2156 cm^?1 and a ν_CC absorption at 1383 cm^?1 that are characteristic of reduced TCNE. The TCNEs have an average central C?C distance of 1.423 Å that is also characteristic of reduced TCNE. The reduced TCNE forms a previously unknown non‐eclipsed, centrosymmetric π‐[TCNE]₂^2? dimer with nominal C₂ symmetry, 12 sub van der Waals interatomic contacts <3.3 Å, a central intradimer separation of 3.039(3) Å, and comparable intradimer C???N distances of 3.050(3) and 2.984(3) Å. The two pairs of central C???C atoms form a ?C?C???C?C of 112.6° that is substantially greater than the 0° observed for the eclipsed D_2h π‐[TCNE]₂^2? dimer possessing a two‐electron, four‐center (2e^?/4c) bond with two C???C components from a molecular orbital (MO) analysis. A MO study combining CAS(2,2)/MRMP2/cc‐pVTZ and atoms‐in‐molecules (AIM) calculations indicates that the non‐eclipsed, C₂ π‐[TCNE]₂^2? dimer exhibits a new type of a long, intradimer bond involving one strong C???C and two weak C???N components, that is, a 2e^?/6c bond. The C₂ π‐[TCNE]₂^2? conformer has a singlet, diamagnetic ground state with a thermally populated triplet excited state with J/k_B=1000 K (700 cm^?1; 86.8 meV; 2.00 kcal mol^?1; H=?2 JS_a?S_b); at the CAS(2,2)/MBMP2 level the triplet is computed to be 9.0 kcal mol^?1 higher in energy than the closed‐shell singlet ground state. The results from CAS(2,2)/NEVPT2/cc‐pVTZ calculations indicate that the C₂ and D_2h conformers have two different local metastable minima with the C₂ conformer being 1.3 kcal mol^?1 less stable. The different natures of the C₂ and D_2h conformers are also noted from the results of valence bond (VB) qualitative diagram that shows a 10e^?/6c bond with one C???C and two C???N bonding components for the C₂ conformer as compared to the 6e^?/4c bond for the D_2h conformer with two C???C bonding components.     

Synthesis,Structure, and Redox Properties of [{(η5-C5H5)Co(S2C6H4)}2Mo(CO)2], a Novel Metalladithiolene Cluster

Metal–metal bond formation by a cobaltadithiolene complex was observed for the first time in the reaction of [Co(η⁵-C₅H₅)(S₂C₆H₄)] with [Mo(CO)₃(py)₃] and BF₃ to give the Co-Mo-Co cluster 1 . Cyclic voltammetry reveals that 1 undergoes two one-electron reduction steps at the Co centers, which is indicative of transmission of the Co−Co electronic interaction through the Mo center.     

Chemo-, regio-, and stereoselectivity in acid-catalyzed hydromethoxylation of tricyclo[4.1.0.0<Superscript>2,7</Superscript>]hept-1-yl and 7-methyltricyclo[4.1.0.0<Superscript>2,7</Superscript>]hept-1-yl phenyl sulfones

Hydromethoxylation of tricyclo[4.1.0.0^2,7]hept-1-yl and 7-methyltricyclo[4.1.0.0^2,7]hept-1-yl phenyl sulfones with methanol at 20°C in the presence of a catalytic amount of perchloric acid is initiated by the endo attack of proton at the C¹ atom, and the subsequent cleavage of the side C¹–C² bond leads to formation of mixtures of diastereoisomeric exo-7-phenylsulfonyl-2-methoxybicyclo[4.1.0]heptanes, the endo-2 isomer prevailing. Probable factors responsible for the observed chemo-, regio-, and stereoselectivity of the addition are discussed.     

Stereoselective synthesis of substituted bicyclo[3.1.1]heptanes: II.* Synthesis of all diastereoisomers of 7-methyl-and 7-phenylbicyclo[3.1.1]hept-6-yl phenyl sulfones from tricyclo[4.1.0.02,7]heptane precursors

All four possible diastereoisomers of 7-methyl-and 7-phenylbicyclo[3.1.1]hept-6-yl phenyl sulfones were intentionally synthesized from tricyclo[4.1.0.0^2,7]heptane and 1-phenyltricyclo[4.1.0.0^2,7]heptane, respectively. The key stage in the synthesis was regio-and stereoselective cleavage of the central bicyclobutane C¹-C⁷ bond in the tricycloheptane precursors by the action of radical, nucleophilic, and electrophilic reagents. The NMR spectra of the diastereoisomers were compared.     

(12,17‐Diethoxy­carbonyl‐2,3,6,­7,11,­18‐hexa­methyl­corrphy­cenato‐­κ4N)iodoiron(III) chloro­form solvate

The title complex, (diethyl 3,4,8,15,19,20‐hexa­methyl‐21,22,23,24‐tetraazopenta­cyclo­[16.2.1.1^2,5.1^7,11.1^14,17]­tetracosa‐1(20),2(22),3,5,7,9,11,13(24),14,16,18‐undecaene‐9,14‐dicarb­oxyl­ate‐κ⁴N)­iodo­iron(III) chloro­form solvate, [Fe(C₃₂H₃₂­N₄O₄)I]·­CHCl₃, shows an almost planar arrangement of the corrphycene moiety with a slightly distorted trapezoid pyramidal core; the Fe^III atom is 0.416 (1) Å from the plane of the C₂₀N₄ system. The Fe—N distances are 2.049 (3), 2.044 (3), 2.079 (3) and 2.075 (3) Å. The solvated chloro­form forms a C—H?O hydrogen bond [C?O 3.107 (10) Å] to an adjacent carbonyl O atom. This is the first X‐ray structure analysis of a corrphycenatoiron(III) derivative.     

Cyclization of nitriles 41. Reaction of arylmethylenemalononitriles with malononitrile; crystal structure of 1-amino-3.5-diphenyl-2,4,4,6,6-pentacyano-1-Cyclohexene

1-Amino-3,5-diaryl-2,4,4,6,6-pentacyano-1-cyclohexenes are prepared by reaction of arylmethylenemalononitriles with malononitrile. The cyclohexene ring of (IVa) has a distorted N₂-C¹=C²-C⁷=N¹ fragment. Steric effects in (IVa) cause a substantial increase in C⁶-C¹ and C³-C⁴ bond length to 1.546(4) and 1.570(4) Å, respectively.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2771–2775, December, 1989.     

The Novel Adamantane Isomer Tricyclo[4.4.0.03,9]decane (2-Homotwistbrendane)

Two synthetic approaches to the novel C₁₀H₁₆ hydrocarbon tricyclo[4.4.0.0^3,9]decane ( 1 ; 2-homotwistbrendane), one of the 19 members of the adamantaneland, and its Lewis-acid-catalyzed rearrangement are described. One route starts from tricyclo[4.3.0.0^3,8]nonan-2-one ( 2 ; 2-twistbrendanone). The missing tenth C-atom is introduced by ring enlargement (Tiffeneau-Demjanov method). Starting from methyl 8,9,10-trinorborn-5-ene-2-endo-carboxylate ( 8 ), ring enlargement by one C-atom, regio- and stereoselective introduction of a C₁ unit to a 2-endo,6-endo-disubstituted bicyclo[3.2.1]octane, and ring closure by acyloin condensation are the key steps in the second approach.     

N‐Benzylnicotinamide and N‐benzyl‐1,4‐dihydronicotinamide: useful models for NAD+ and NADH

3‐Aminocarbonyl‐1‐benzylpyridinium bromide (N‐benzylnicotinamide, BNA), C₁₃H₁₃N₂O⁺·Br⁻, (I), and 1‐benzyl‐1,4‐dihydropyridine‐3‐carboxamide (N‐benzyl‐1,4‐dihydronicotinamide, rBNA), C₁₃H₁₄N₂O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)⁺ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low‐temperature high‐resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)⁺ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition‐state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom.