Generation and reactions of two new functionalized tricyclo[3.3.0.0 3,7]oct-1(5)-ene derivatives

The generation of the new functionalized and highly pyramidalized alkenes, 3,7-(2,2'-biphenylene)tricyclo[3.3.0.0(3,7)]oct-1(5)-ene (20) and 3,7-sulfonyldioxytricyclo[3.3.0.0(3,7)]oct-1(5)-ene (39), and their trapping with 1,3-diphenylisobenzofuran and 11,12-dimethylene-9,10-dihydro-9,10-ethanoanthracene are described. While both alkenes 20 and 39 failed to give the expected cyclobutane or diene dimers, 20 was reacted with 3,7-dimethyltricyclo[3.3.0.0(3,7)]oct-1(5)-ene (1b) to give the cross-coupled product 4,5-(2,2')-biphenylene-10,11-dimethylpentacyclo[8.2.1.1(2,5).1(4,7).1(8,11)]hexadeca-1,7-diene (33). DFT calculations [B3LYP/6-31G(d)] on compound 20 gave important parameters of this pyramidalized alkene, such as the pyramidalization angle (61.7 degrees), the strain energy (72.9 kcal/mol), and the HOMO/LUMO gap (3.79 eV).     

Generation and trapping of tricyclo[3.3.0.0]oct-1(5)-ene derivatives containing carbonyl functionalities

Two new functionalized highly pyramidalized tricyclo[3.3.0.0^3,7]oct-1(5)-ene derivatives containing carbonyl functionalities have been trapped as Diels-Alder adducts, although they failed to dimerize. An interesting fragmentation of the bisnoradamantane skeleton to norbornane derivatives has also been observed.     

Diels-Alder reactions of highly pyramidalized tricyclo[3.3.0.0]oct-1(5)-ene derivatives: further chemistry of pentacyclo[6.4.0.0.0.0]dodeca-5,8,11-triene

A study of the trapping of highly pyramidalized tricyclo[3.3.0.0^3,7]oct-1(5)-ene derivatives (generated from a 1,2-diiodo precursor on reaction with t-BuLi, 0.45% sodium amalgam and molten sodium) with different dienes (11,12-dimethylene-9,10-dihydro-9,10-ethanoanthracene, 1,3-diphenylisobenzofuran, 2,5-dimethylfuran and furan) is presented. Byproducts from the trapping of pentacyclo[6.4.0.0^2,10.0^3,7.0^4,9]dodeca-5,8,11-triene with 1,3-diphenylisobenzofuran have been synthesized and fully characterized, including an X-ray diffraction analysis. Also, the above triene has been cross coupled with 3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1(5)ene to give a tetrasecododecahedratetraene derivative.     

Novel 2-phosphabicyclo[2.2.2]oct-5-ene derivatives and their use in phosphinylations

The [4 + 2] cycloaddition of the double-bond isomers ( A and B ) of dihydrophosphinine oxide 1 afforded novel phosphabicyclo[2.2.2]oct-5-ene derivates ( 2–4 ), formation of which was justified by PM3 semiempirical calculations. The compounds of dimer type ( 2–4 ) were utilized in the UV light-mediated fragmentation-related phosphinylation of nucleophiles, especially in that of alcohols. To explore the role of structural modifications on the fragmentation ability, disulfide 5 , phosphabicyclooctane 7 obtained by the hydrogenation of 2 , and the adduct of dihydrophosphinine oxide 1 with benzoquinone ( 7 ) were also synthesized and tested in fragmentation. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:97–106, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10221     

A highly regio- and stereoselective formation of bicyclo[4.2.0]oct-5-ene derivatives through thermal intramolecular [2 + 2] cycloaddition of allenes

Thermal [2 + 2] cycloaddition of allenes with an additional multiple bond is described. By simply heating the allenenes or allenynes having a three-atom tether in an appropriate solvent such as dioxane or DMF, the distal double bond of the allenic moiety regioselectively participates in the cycloaddition to form bicyclo[4.2.0]oct-5-ene derivatives in good to excellent yields. In all the reactions of allenenes, the olefin geometry was completely transferred to the cycloadducts. While the reaction of terminal allenes afforded bicyclic cyclobutane derivatives as a single isomer, the cycloaddition of some internal allenes with axial chirality yielded a diastereomeric mixture of cycloadducts. These results are in good accordance with the stepwise mechanism through a biradical intermediate with a coplanar allyl radical.     

Synthesis and spectroscopic studies of some new oxazepine derivatives throughout [2+5] cycloaddition reactions (III)

The present work included condensation reactions of o-tolidine with different aromatic aldehydes in absolute ethanol to give Schiff bases (w ₉ –w ₁₂ ) in high yield which, on reaction with maleic and phthalic anhydride by [2+5] cycloaddition reactions in the presence of suitable solvents, give the corresponding [1,3]oxazepine-4,7-dione (w ₉ m–w ₁₂ m) and [1,3]oxazepine-1,5-dione (w ₉ ph–w ₁₂ ph), respectively. The structure of the newly synthesized compounds were monitored by TLC and established on the basis of elemental analysis, FT-IR, and ¹H NMR.     

Kinetics and mechanism of the thermal reactions of endo- and exo-5-cyanobicyclo[2.2.2]oct-2-ene and methyl-substituted derivatives in the gas phase

The thermal reactions of endo- and exo-5-cyanobicyclo-[2.2.2]oct-2-ene and their trans- and cis-6-methyl-substituted derivatives have been investigated in the gas phase between 518 and 630 K. Each product decomposes by two parallel first-order retro-Diels-Alder reactions, a main one with formation of cyclohexa-1,3-diene and a minor one with elimination of ethene. Slight isomerizations are also observed. The kinetic results can be explained in terms of a biradical mechanism. The rate-determining step is shown to depend on the amount of resonance energy in the biradical. Heats of formation and entropies of the bicyclo[2.2.2]oct-2-enes studied are estimated.     

Synthesis of tetracyclo[3.3.0.02.4.03.6]oct-7-ene and some of its derivatives

A full account is given of the synthesis of the title compound, its 7,8-dihydro-analogue and of some of its derivatives.     

Metathesis polymer based on 5-trimethylsilylbicyclo[2.2.2]oct-2-ene: Synthesis and gas-transport properties

A new silicon-containing bicyclic monomer 5-trimethylsilylbicyclo[2.2.2]oct-2-ene has been synthesized, and its metathesis polymerization and gas transport properties of the polymer based on it have been studied. The monomer is synthesized by the two-step scheme using the Diels–Alder reaction from 1,3-cyclohexadiene and vinyltrichlorosilane followed by methylation with a Grignard reagent. The resulting 5-trimethylsilylbicyclo[ 2.2.2]oct-2-ene is inactive in metathesis homopolymerization in the presence of first- and second- generation Grubbs catalysts and a Hoveyda–Grubbs catalyst, but it slowly polymerizes when norbornene is present in the reaction mixture. The high-molecular-mass copolymer (M _w = 3.0 × 10⁵, M _w/M _n = 2.8) of 5-trimethylsilylbicyclo[2.2.2]oct-2-ene and norbornene possesses good film-forming properties, and its glass transition temperature is 126°C. The gas-transport properties of the copolymer have been studied.     

Synthesis and crystal structure of 5-amino-4,6-dicyano-3-dicyanomethylene-1, 8,8-trimethyl-2-azabicyclo[2.2.2]oct-5-ene

5-Amino-4,6-dicyano-3-dicyanomethylene-1,8,8-trimethyl-2-azabicyclo[2.2.2]oct-5-ene has been synthesized. The molecular and crystal structure of this compound has been determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 169–172, January, 1996.     

2D 1H and 13C NMR evidences of the [2 + 2] autodimerization of 2-benzyl-5-benzylidene cyclopentanone yielding two different diphenyl,dispiro cyclobutane derivatives

The ene-ene [2 + 2] cycloaddition of 2-benzyl-5-benzylidenecyclopentanone proceeds smoothly and spontaneously in benzene-d6 or deuteriochloroform solution to give two different diphenyl dispiro [4.1.4.1] dodecan-4,11-diones. Detailed 1H and 13C 2DNMR spectroscopy (COSY, HMQC, HMBC) were performed in order to prove the existence in solution of two cyclobutane derivatives, one a previously described photodimer obtained by the UV irradiation of crystals of 2-benzyl-5-benzylidenecyclopentanone.     

Rhodium N-heterocyclic carbene-catalyzed [4 + 2] and [5 + 2] cycloaddition reactions

[reactions: see text] A rhodium complex of N-heterocyclic carbene (NHC) has been developed for intra- and intermolecular [4 + 2] and intramolecular [5 + 2] cycloaddition reactions. This is the first use of a transition-metal NHC complex in a Diels-Alder-type reaction. For the intramolecular [4 + 2] cycloaddition reactions, all the dienynes studied were converted to their corresponding cycloadducts in 91-99% yields within 10 min. Moreover, up to 1900 turnovers have been obtained for the intramolecular [4 + 2] cycloaddition at 15-20 degrees C. For the intermolecular [4 + 2] cycloadditions, high yields (71-99%) of the corresponding cycloaddition products were obtained. The reaction time and yield were highly dependent upon the diene and the dienophile. For the intramolecular [5 + 2] cycloaddition reactions, all the alkyne vinylcyclopropanes studied were converted to their corresponding cycloadducts in 91-98% yields within 10 min. However, the catalytic system was not effective for an intermolecular [5 + 2] cycloaddition reaction.     

[4+2] Cycloaddition reactions of 1-alkyl-2,3,4,5-tetraphenylphosphole derivatives

Russian Chemical Bulletin - The [4+2] cycloaddition reactions of 1-alkyl-2,3,4,5-tetraphenylphosphole derivatives with N-phenylmaleimide were studied for the first time. The reactions of...     

NMR structural elucidation and photochromic behavior of new 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives

Several 6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene derivatives having various substituents on C² were synthesized, and their ¹H NMR spectra and photochromic behavior were examined.     

Rh-catalyzed [5+1] and [4+1] cycloaddition reactions of 1,4-enyne esters with CO: a shortcut to functionalized resorcinols and cyclopentenones

We have developed novel Rh-catalyzed [n+1]-type cycloadditions of 1,4-enyne esters, which involve an acyloxy migration as a key step. The efficient preparation of functionalized resorcinols, including biaryl derivatives, from readily available 1,4-enyne esters and CO was achieved by Rh-catalyzed [5+1] cycloaddition accompanied by 1,2-acyloxy migration. When enyne esters had an internal alkyne moiety, the reaction proceeded by a [4+1]-type cycloaddition involving 1,3-acyloxy migration, leading to cyclopentenones.     

Photochemical reaction of 5-dicyanomethylenebicyclo[2.2.2]oct-2-ene as a model for a light-energy conversion and storage system

Upon irradiation, 5-dicyanomethylenebicyclo[2.2.2]octene ($\text{3}$) gives a highly strained compound, 2,2-dicyanotricyclo[4.2.1.0^1,3]nonene ($\text{6}$) in good yield. Of additional interest is the observation that the starting material $\text{3}$ can be quantitatively regenerated from the photo-product $\text{6}$ with release of 28.8 kcal/mol.     

Transition metal-catalyzed intermolecular [5+2] and [5+2+1] cycloadditions of allenes and vinylcyclopropanes

Initial examples of the intermolecular Rh(I)-catalyzed [5+2] cycloaddition reaction of bifunctional allenes and vinylcyclopropanes are described. The reactions proceed with facility and in yields of up to 99% with a variety of alkyne-, ester-, styrene-, or cyano-substituents on the allene to afford the corresponding cycloadducts. In the presence of CO, the reaction proceeds to an eight-membered ring cycloadduct and its transannularly closed product, providing the first example of a three-component [5+2+1] cycloaddition with allenes.