A convenient route to prepare isodicyclopentadiene—precursor of 1,5-dihydro-pentalene

A new route to prepare tricyclo[5.2.1.0^2,6]deca-2,4-diene (isodicyclopentadiene) was developed. This new route passes through a brominated (5-bromotricyclo[5.2.1.0^2,6]dec-3-ene) derivative obtained from tricycle[5.2.1.0^2,6]dec-3-ene (8,9-dihydrodicyclopentadiene) and NBS with a good yield. The complete assignment of protons and carbons on nuclear magnetic resonance spectra was done for dicyclopentadiene and the chemically transformed compounds by 2D NMR techniques.     

Molecular diversity from aromatics. A tandem oxidative dearomatization,cycloaddition and reactivity modulation in excited states: synthesis of tricyclo[5.3.1.0]undecanes and bicyclo[4.2.0]octanes from common precursors

Stereoselective route to tricyclo[5.3.1.0^1,5]undecane and bicyclo[4.2.0]octane ring systems present in the molecular structure of tricycloillicinone, cedrenoids and endiandric acid, elysiapyrones, respectively, is described. A tandem oxidative dearomatization of o-hydroxymethylphenol, π⁴s+π²s cycloaddition, reactivity modulation in excited state and ring-closing metathesis are the key features of our approach.     

Synthesis of Tricyclic Skeletons Mediated by (Diene)Fe(CO)3 Complexes

Sequential additions of carbon nucleophiles to the (η⁵-pentadienyl)Fe(CO)₃ cation afforded tricyclo[6.3.0.0^2.6]undecane, tricyclo[6.4.0.0^2.6]dodecane, tricyclo[7.3.0.0^2.7]dodecane and tricyclo[7.4.0.0^2.7]-tridecane derivatives. The same strategy can also be applied to construct heterotricyclic skeletons.     

Omriolide A and B; two new rearranged spongian diterpenes from the marine sponge Dictyodendrilla aff. retiara

Two new rearranged spongian diterpenes designated omriolide A and B were isolated from the southern Kenyan sponge Dictyodendrilla aff. retiara collected at Wasini Is., Shimoni Channel. Omriolide A possesses an octalin linked to a unique trioxatricyclo[5.2.1.0^4,10]decane ring system, forming a tricyclic ‘cap’. Omriolide B comprised a tricyclo[5.4.0.0^2,4]undecane linked to a dioxabicyclo[3.3.0]octane. The structures of both diterpenes were elucidated by interpretation of MS results and, mainly, 1D and 2D NMR spectra.     

Synthesis, structural characterization, and skeletal rearrangement of dibenzo tricyclo[3.3.0.0]-1,2,5,6-tetrasubstituted octanes

Dibenzo tricyclo[3.3.0.0^2,6]-1,2,5,6-tetrasubstituted octanes, the ‘twisted’ highly strained valence isomers of substituted dibenzo[a,e]cyclooctatetraenes, were synthesized and their structure characterized by single-crystal X-ray analysis. Their skeletal rearrangement was experimentally observed.     

Zur Photochemie von (Z,Z)-2,7-Cyclodecadien-1-on und 4,8-Cyclododecadien-1-on. Synthese und Eigenschaften von Tricyclo[5.3.0.02,8]decan-Systemen

On the Photochemistry of (Z,Z)-2,7-Cyclodecadien-1-one and 4,8-Cyclododecadien-1-one. Synthesis and Properties of Tricyclo[5.3.0.0^2,8]decane Systems Irradiation of (Z,Z)-2,7-cyclodecadien-1-one ( 3 ) yields (Z,Z)-3,7-cyclodecadien-1-one ( 12 ) or tricyclo-[5.3.0.0^2,8]decan-4-one ( 16 ), depending on the reaction conditions. Irradiation of 4,8-cyclododecadien-1-one ( 28 ) results also in a light-induced transannular [2 + 2] cycloaddition, yielding tetracyclo[7.3.0.0^2,100^3,6]dodecan-1-one ( 30 ). Starting from 16 , the preparation of tricyclo[5.3.0.0^2,8]dec-4-ene ( 19 ), tricyclo[5.3.0.0^2,8]dec-4-ene ( 21 ) and tricyclo[5.3.0.0^2,8]deca-3,5-diene ( 24 ) is described. The ¹H-NMR and ¹³C? NMR spectra of the newly prepared compounds are discussed. In the case of 19, 21 , and 24 , the electronic structure is discussed on hand of their PE spectra.     

Quantum chemical study of the structure of tricyclic saturated hexafluoro-1,3-butadiene dimers

Results of a quantum-chemical study of the molecular structure of dimerization products of saturated 1,3-butadiene and hexafluoro-1,3-butadiene (tricyclo[3.3.0.0^2.6]octane, dodecafluorotricyclo[4.2.0.0^2.5]octane (I), and dodecafluorotricyclo[3.3.0.0^2.6]octane (II)) are presented. The calculated symmetry of the molecule of I in vacuum (C ₂) differs from its symmetry in the single crystal (C _b , XRD). The most stable of dimers (II) contains C-C bonds with a length of up to 1.573 Å and a four-atom cycle with angles of 82.3°.     

Synthesis of polycyclic cyclopropanecarboxylic acids and their esters based on catalytic cyclopropanation of 6,6-dimethylfulvene

Reactions of 6,6-dimethylfulvene with methyl diazoacetate in the presence of Cu compounds is accompanied by methoxycarbonylmethylenation of the endocyclic double bonds to give the corresponding mono- and diadducts in total yields of up to 85% with marked predominance ofanti-isomers. The subsequent cyclopropanation of monoadducts with diazomethane in the presence of Pd compounds also involves the endocyclic double bond and gives esters of tricyclo[4.1.0.0.^2,4]heptanecarboxylic acid in high yields. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 528–531, March, 1997.     

Synthesen von Tricyclo [5.2.1.04,8]decan (2-Homobrendan)

Syntheses of Tricyclo [5.2.1.0^4,8]decane (2-Homobrendane) Three different approaches to tricyclo [5.2.1.0^4,8] decane (5) (and derivatives thereof), one of the 19 isomeric hydrocarbons of the ‘adamantaneland’, are described: (1) Cyclization of properly functionalized bicyclo [3.2.1]octanes as 32 (cyclialkylation), 40+42 (thermocyclization) and 44+45 (photocyclization); (2) Silver-(I)-ion catalyzed rearrangement of 5,7- and 5,10-Dehydroprotoadamantane ( 63 and 64 , respectively) yielding tricyclo[5.2.1.0^4,8]dec-2- (39) and -5-ene (59) , respectively; (3) Thermal eliminative rearrangement of the 10endo-p-toluenesulfonate and -methanesulfonate of protoadamantane ( 71 and 72 ) and protoadamant-4-ene ( 76 and 77 ), respectively, yielding tricyclo [5.2.1.0^4,8]dec-2-ene (39) and -2, 5-diene (15) , respectively.     

Complex Carbocyclic Skeletons from Aryl Ketones through a Three-Photon Cascade Reaction

Starting from readily available 7-substituted 1-indanones, products with a tetracyclo[5.3.1.0^1,70^4,11]undec-2-ene skeleton were obtained upon irradiation at λ=350 nm (eight examples, 49–67 % yield). The assembly of the structurally complex carbon framework proceeds in a three-photon process comprising an ortho photocycloaddition, a disrotatory [4π] photocyclization, and a di-π-methane rearrangement. The flat aromatic core of the starting material is converted into a functionalized polycyclic hydrocarbon with exit vectors in three dimensions. Ring opening reactions at the central cyclopropane ring were explored, which enable the preparation of tricyclo[5.3.1.0^4,11]undec-2-enes and of tricyclo[6.2.1.0^1,5]undecanes.     

The Adamantane Rearrangement of Tricyclo[4.2.2.01,5]decane to Tricyclo[5.3.0.04,8]decane

Regioselective generation of the C(2)-carbocation a of tricyclo[4.2.2.0^1,5]decane ( 1 ) by treatment of both corresponding epimeric alcohols 5 and 6 with BF₃ and trapping the rearranged tricyclo[5.3.0.0^4,8]decan-7-yl carbocation b with Et₃SiH as hydride-ion donor (ionic hydrogenation) gives the corresponding hydrocarbon 3 as sole product in almost quantitative yield. The latter is a known intermediate in the Lewis-acid-catalyzed rearrangement of 1 to adamantane ( 4 ).     

Complex Carbocyclic Skeletons from Aryl Ketones through a Three‐Photon Cascade Reaction

Starting from readily available 7‐substituted 1‐indanones, products with a tetracyclo[5.3.1.0^1,70^4,11]undec‐2‐ene skeleton were obtained upon irradiation at λ=350 nm (eight examples, 49–67 % yield). The assembly of the structurally complex carbon framework proceeds in a three‐photon process comprising an ortho photocycloaddition, a disrotatory [4π] photocyclization, and a di‐π‐methane rearrangement. The flat aromatic core of the starting material is converted into a functionalized polycyclic hydrocarbon with exit vectors in three dimensions. Ring opening reactions at the central cyclopropane ring were explored, which enable the preparation of tricyclo[5.3.1.0^4,11]undec‐2‐enes and of tricyclo[6.2.1.0^1,5]undecanes.     

The synthesis of 2,6-dimethylenetricyclo[3.3.0.03,7]octane

The synthesis of the title compound is reported together with that of 2-methyl-6-methylenetricyclo[3.3.0.0^3,7]octane. During the synthesis a rearrangement of the tricyclo[3.3.0.0^3,7]octane skeleton to the tricyclo[3.2.1.0^3,6]octane system has been observed.     

Photochemische Umwandlungen. XV [1] Photochemische Isomerisierung des exo-Tricyclo[4.2.1.02′5]nona-3,7-dien-Systems. Vorläufige Mitteilung

The acetone sensitized isomerization of two exo-tricyclo[4.2.1.0^2,5]nonadiene derivatives, of the corresponding tricyclo[4.3.0.0^2,5]nonadienes, and the photoisomerization of two bicyclo[4.3.0]nonatrienes by direct excitation are described.     

Tricyclo [3.3.2.03,7]decan (9-Homo-nor-adamantan) Synthese und Umwandlungen

Tricyclo[3.3.2.0^3,7]decane (9-Homo-nor-adamantane). Synthesis and Transformations A synthesis of tricyclo [3.3.2.0^3,7]decane (=9-homo-nor-adamantane; 1 ), which belongs to the adamantaneland, a family of nineteen isomeric C₁₀H₁₆ hydrocarbons, is described, as well as derivatives thereof. Treatment of protoadamantan-5endo-ol (11) with either thionyl chloride or phosphorus pentachloride yielded under rearrangement the chloride 18 , and solvolysis of the 5endo-chloro-protoadamantane (16) led to the acetate 26, 18 and 26 having both the tricyclo [3.3.2.0^3,7]decane skeleton. Subsequent transformations gave the title compound 1 as well as the corresponding olefin 8 .     

13C NMR spectra of tricyclo[4.2.1.02,5]nonanes and tetracyclo[5.4.1.02,6.08,11]dodecanes

The ¹³C NMR spectra of tricyclo[4.2.1.0^2,5]nonanes and tetracyclo[5.4.1.0^2,6.0^8,11]dodecanes and their dimethyl derivatives were measured to demonstrate the four-membered ring annelation effects on the bicyclo[2.2.1]heptane skeleton, and the steric δ-syn effects of the methyl groups attached to the four-membered ring on the bridge carbons in these systems.     

The relative merits of 6π9C bishomoaromatic and 10π13C longicyclic stabilization

The behaviour of tricyclo[4.4.3.0^1,6] tridecapentaenyl and tricyclo[4.4.3.0^1,6]trideca- 2,4,11-trienyl cations under short- and long- life conditions is described.     

The effect of the α-cyano moiety on neighboring group participation by the cyclopropyl group

H/α-CN rate ratios have been derived for the solvolysis of sulfonate esters of endo-tricyclo[3.2.1.0^2,4]octan-anti-8-ol and tricyclo[2.2.1.0^2,6]heptan-3-ol. The role of the α-cyano moiety in the stabilization of highly delocalized cations has been evaluated.     

Accurate prediction of 195Pt-NMR chemical shifts for hydrolysis products of [PtCl6]2− in acidic and alkaline aqueous solutions by non-relativistic DFT computational protocols

The ¹⁹⁵Pt-NMR chemical shifts of all possible hydrolysis products of [PtCl₆]^2? in acidic and alkaline aqueous solutions are calculated employing simple non-relativistic density functional theory computational protocols. Particularly, the GIAO-PBE0/SARC-ZORA(Pt) ∪ 6-31 + G(d)(E) computational protocol augmented with the universal continuum solvation model (SMD) performs the best for calculation of the ¹⁹⁵Pt-NMR chemical shifts of the Pt(IV) complexes existing in acidic and alkaline aqueous solutions of [PtCl₆]^2?. Excellent linear plots of δ_calcd(¹⁹⁵Pt) chemical shifts versus δ_exptl(¹⁹⁵Pt) chemical shifts and δ_calcd(¹⁹⁵Pt) versus the natural atomic charge Q_Pt are obtained. Very small changes in the Pt–Cl and Pt–O bond distances of the octahedral [PtCl₆]^2?, [Pt(OH)₆]^2?, and [Pt(OH₂)₆]⁴⁺ complexes have significant influence on the computed σ^{iso 195}Pt magnetic shielding tensor elements of the anionic [PtCl₆]^2? and the computed δ ¹⁹⁵Pt chemical shifts of [Pt(OH)₆]^2? and [Pt(OH₂)₆]⁴⁺. An increase of the Pt–Cl and Pt–O bond distances by 0.001 Å (1 mÅ) is accompanied by a downfield shift increment of 17.0, 19.4, and 37.6 ppm mÅ^?1, respectively. Counter-anion effects in the case of the highly positive charged complexes drastically improve the accuracy of the calculated ¹⁹⁵Pt chemical shifts providing values very close to the experimental ones.     

Density functional study of tricyclo[3,3,1,13,7]decane and tricyclo[3,3,1,13,7]decsilane and their halogen derivatives

The B3LYP/3‐21G* ab initio molecular orbital method from the Gaussian 94 computer program package was applied to study tricyclo[3,3,1,1^3,7]decane and tricyclo[3,3,1,1^3,7]decsilane molecules and their halogen derivatives (1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane, C₁₀H₁₂X₄, and Si₁₀H₁₂X₄). The optimized structures of these compounds were obtained. Ionization potentials, HOMO and LUMO energies, energy gaps, heats of formation, atomization energies, and vibration frequencies were calculated. These calculations indicate that these molecules are stable and have T_d symmetry. Tricyclo[3,3,1,1^3,7]decsilane and its halogen derivatives (Si₁₀H₁₂X₄) are found to have higher conductivity than that of tricyclo[3,3,1,1^3,7]decane and its halogen derivatives (C₁₀H₁₂X₄). 1,3,5,7‐Tetraflourotricyclo[3,3,1,1^3,7]decane (C₁₀H₁₂F₄) and 1,3,5,7‐tetraflourotricyclo[3,3,1,1^3,7]decsilane (Si₁₀H₁₂F₄) were found to be the easiest compounds to form and the most difficult to dissociate of all 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane compounds, respectively. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 189–198, 1999