Carbon-13 chemical shifts of bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives

¹³C chemical shifts of more than fifty bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives (hydrocarbons, alcohols, ketones and esters) have been determined. The usefulness of ethyl derivatives for the assignment of close ¹³C chemical shifts in bicyclic methyl derivatives is shown both for the bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane series. Comparison of substituent effects on α-, β-, γ- and δ-carbons in both series of compounds shows remarkable differences in steric interactions. In contrast to the rigid bicyclo[2.2.1]heptane system, both chair and boat conformations can be predominant in the bicyclo[3.2.1]octane series with the conformationally flexible 6-membered ring.     

Synthetic approach to preparation of indole derivatives fused with a bicyclo[3.3.1]nonane framework

Starting with Δ¹⁵-17-ketosteroids, applying Normant reaction with allylmagnesium bromide and anionic Cope rearrangement of the formed allyl alcohol, 15α-derivatives of androstane series were prepared. The latter were brought into Wittig reaction with an ylide generated from ethyltriphenylphosphonium bromide, and the product was subjected to ene reaction to provide 15α-substituted pregnanes.     

Synthesis of 1,10-phenanthrolines fused with bicyclo[3.3.0]octane and bicyclo[3.3.1]nonane frameworks

Reactions of bicyclo[3.3.1]nonane-2,6-dione and bicyclo[3.3.0]octane-3,7-dione with 8-amino-7-quino-linecarbaldehyde under basic conditions led to fused nonplanar compounds with one or two 1,10-phenanthroline moieties. The novel heterocyclic systems bicyclo[3.3.1]nonano[2,3-b]bis[1,10]-phenanthroline, cis-bicyclo[3.3.0]octano[3,2-b:7,6-b']bis[1,10]phenanthroline, bicyclo[3.3.1]nona-no[2,3-b:6,7-b']bis[1,10]phenanthroline, and 8H-9,16-methanoindolo[2',3':5,6]cycloocta[1,2-b]bis-[1,10]-phenanthroline have been synthesized and characterized.     

Synthesis of bridgehead hydroxy bicyclo[2.2.2]octane derivatives

Two independent synthetic routes, starting from 1,3-cyclohexadione, toward the 4-hydroxy bicyclo[2.2.2]octane-2,6-dione derivative 3 are described.     

Synthesis of novel spiro-cyclohexene bicyclo[2.2.2]octane derivatives

A methodology for the synthesis of novel spiro-cyclohexene bicyclo[2.2.2]octane derivatives, including Claisen rearrangement and ring-closing metathesis (RCM) as key synthetic steps, is described.     

Regiocontrolled synthesis of bicyclo[3.2.1]octane derivatives by cuprate addition and intramolecular acylation

Copper-catalysed reaction of 4-butenylmagnesium bromide with cyclohexenones (2) and (5) occurs with intramolecular acylation of the intermediate enolate to give bicyclo[3.2.1]octane derivatives (4) and (6).     

Synthesis of highly functionalised enantiopure bicyclo[3.2.1]- octane systems from carvone

The commercially available monoterpene carvone has been efficiently converted into the tricyclo[3.2.1.0(2.7)]octane and bicyclo[3.2.1]octane systems characteristic of some biologically active compounds. The sequence used for this transformation involves as key features an intramolecular Diels-Alder reaction of a 5-vinyl-1,3-cyclohexadiene and a cyclopropane ring opening.     

Molecular and crystal structure of indole derivatives fused with substituted bicyclo[3.3.1]nonane

Molecular structures of oxime 6-oxo-indolo[2,3-b]-bicyclo[3.3.1]non-2-en 1 and 6-oxo-(5-methoxy-indolo[2,3-b])-bicyclo[3.3.1]non-2-en 2 were determined by X-ray crystal investigation. It was revealed that oxime 1 has anti-configuration in respect to indole-containing framework, and both compounds adopt half-chair–chair-conformation. The distortion of rings was evaluated by calculation of the ZP- and CP-puckering parameters. The presence of the methoxy-group in compound 2 was found to lead to the changes in molecular packing in comparison with structure 1.     

Silver-promoted reactions of bicyclo[3.2.1]octadiene derivatives

[reaction: see text] Highly substituted bicyclo[3.2.1]octadiene building blocks are easily prepared from tetrachloro- or tetrabromocyclopropene through reaction with cyclic dienes. These polyhalogenated derivatives can serve as precursors to a variety of functionalized bridged bicyclic compounds. Herein, we report on the generation and reaction of electrophilic species with silver ion.     

The stereochemistry of bicyclo[3.2.1]-octane—XII The photohalogenation of bicyclo[3.2.1]octene-2 derivatives

The light-initiated halogenation of bicyclo[3.2.1]octene-2, its 3-phenyl and 3-bromo derivatives with N-bromosuccinimide and t-butyl hypochlorite resulted in the exclusive formation of the exo-4-halobicyclo[3.2.1]octene-2-derivatives.     

Oxabicyclo[3.2.1]octane derivatives as highly reactive dienophiles: synthesis of bicyclo[5.n.0] systems

[reaction: see text] We have developed highly versatile, homochiral oxabicyclo[3.2.1]octadiene building blocks for the synthesis of natural products. We have found that these bridged alkenes undergo exceptionally facile Diels-Alder reactions and react faster than several well studied bicyclo[2.2.1]heptene dienophiles. The reaction proceeds with high levels of stereochemical control and in very good to excellent yields, providing access to bicyclo[5.4.0]undecane and bicyclo[5.3.0]decane systems. This reactivity is attributed to strain and homoconjugation effects.     

Synthesis of crownophane with the bicyclo[2.2.2]octane core

Russian Chemical Bulletin -     

Cationic polymerization of 6,8-dioxabicyclo-[3.2.1]octane and 3,6,8-trioxabicyclo[3.2.1]octane

6,8-Dioxabicyclooctane (DBO) and 3,6,8-trioxabicyclooctane (TBO) underwent ring-opening polymerization when treated with PF₅ in dichloromethane at ?78°C. These conditions were outstandingly effective for the polymerization of these bicyclic monomers, as shown by systematic variation of catalyst, solvent, and temperature. Best results were 68–84% yields of poly-DBO, η_inh 0.26–0.33 dl/g, and ～100% yield of poly-TBO, η_inh 0.56–0.80 dl/g. The relationship of these results to those of previous investigators of DBO discussed.     

Unusual ring-chain tautomerism in bicyclo[4.2.0]octane derivatives

A new type of ring-chain tautomerism, which consists of the reversible conversion of bicyclo[4.2.0]octane derivatives into trisubstituted enamines was found and studied by ¹H NMR spectroscopy. The starting materials were prepared by the stereoselective reaction of (E)-3,3,3-trichloro-1-nitropropene with cyclohexanone enamines.     

Synthesis of a substituted 6,8-dioxabicyclo[3.2.1]octane

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 692–693, May, 1991.     

Synthesis and reactivity of bicyclo[3.2.1]octanoid-derived cyclopropanes

Photochemical oxa-di-π-methane rearrangement of bicyclo[3.2.1]octanoid scaffolds affords multifunctional, donor-acceptor cyclopropanes. A related photochemical reaction of an iminium ether substrate uncovered an unprecedented aza-di-π-methane rearrangement of a β,γ-unsaturated iminium. Donor-acceptor cyclopropanes have been evaluated as substrates for reactions generating several new chemotypes.     

Asymmetric sequential Michael reaction: Synthesis of optically active bicyclo[2.2.2]octane derivatives

The sequential Michael reaction of (S)-4,5-di-O-isopropylidenepent-2- enoate and with lithium enolate afforded diastereo- and enantioselectively bicyclo[2.2.2]octane and (or ), respectively. The adducts were efficiently converted into both enantiomeric keto aldehydes (−)- and (+)- .     

Efficient synthesis of 8-oxa-bicyclo[3.2.1]octane derivatives from d-arabinose

Our studies of the TIBAL-promoted Claisen rearrangement reaction and ring-closing metathesis (RCM) resulted in the development of an efficient synthetic route to polyfunctional seven-membered carbasugar synthons from d-arabinose. Moreover, the construction of 8-oxa-bicyclo[3.2.1]octane derivatives 10 and 13 was achieved by BCl₃ or iodide-promoted intramolecular electrophilic addition reactions, which were regio- and stereoselective.     

Vibrational circular dichroism DFT study on bicyclo[3.3.0]octane derivatives

The absolute configurations of four bicylco[3.3.0]octane derivatives: endo-bicyclo[3.3.0]octane-2,6-diol, endo-2,6-diacetoxybicyclo[3.3.0]octane, endo-bicyclo[3.3.0]octane-2,6-dione and bicyclo[3.3.0]octa-2,6-dien-2,6-bistriflate were studied by vibrational circular dichroism (VCD). These chiral derivates are of interest as intermediates in the asymmetric synthesis of enantiomerically pure natural products and chiral ligands for asymmetric catalysis. VCD has been used to determine the absolute configuration of each compound, proving the capability of VCD for molecules with several stereogenic centres. IR and VCD spectra have been simulated at the B3LYP/6-31G¹ level for all possible diastereomers. Based on the agreement between the experimental and the calculated spectrum, the stereochemistry of each compound could be assigned. The predicted absolute configurations are found to agree with literature data.