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1.
The first total syntheses of the racemates of naturally occurring macrophyllin-type bicyclo[3.2.1]octanoid neolignans, kadsurenin C 3 and kadsurenin L 4, were accomplished starting from vanillin and resorcinol. The acid-catalyzed rearrangement of hydrobenzofuranoid neolignans into bicyclo[3.2.1]octanoid neolignans was used as the key step. 相似文献
2.
[reaction: see text] The total synthesis of racemic clavubicyclone (1), which was isolated from Okinawan soft coral by our group, is described. The bicyclo[3.2.1]octane skeleton was prepared by Cope rearrangement of a divinylcyclopropane derivative. Three functional groups on the skeleton were constructed by Barton decarboxylation, Wittig reaction, and alkylation. 相似文献
3.
Dicarbonyl(pentane-2,4-dionato)rhodium(I) does not form a complex with, or induce a skeletal rearrangement in, cycloheptatriene. 5-Exo-methylene-2-norbornene is present as an impurity in cycloheptatriene and is complexed by Rh(I) complexes as its endocyclic tautomer. Rhodium complexes of 1,3,5-cyclooctatriene, bicyclo [3.2.1] octa-2,6-diene, cyclooctatetraene, cyclooctatetraene epoxide, bicyclo [6.1.0] nonatriene and 9,9-dimethyl bicyclo [6.1.0] nonatriene are also reported. 相似文献
4.
《Tetrahedron letters》1987,28(50):6343-6346
Trimethylsilyl group substituted bicyclo[2.2.2]octane derivatives were synthesized and subjected to TMS group directed Wagner-Meerwein rearrangement to give bicyclo[3.2.1]octene derivatives in high yields. 相似文献
5.
Alan R. Burns Ama?l G. E. Madec Darryl W. Low Iain D. Roy Hon Wai Lam 《Chemical science》2015,6(6):3550-3555
2,2-Disubstituted cyclic 1,3-diketones containing a tethered electron-deficient alkene undergo chiral phosphoric acid-catalyzed desymmetrizing Michael cyclizations to give bridged bicyclic products in high enantioselectivities. Both bicyclo[3.2.1]octanes and bicyclo[3.3.1]nonanes are accessible using this methodology. 相似文献
6.
[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. 相似文献
7.
Qiuyu Li Jiajia Li Jie Zhang Shu Wu Yu Zhang Prof. Dr. Aijun Lin Prof. Dr. Hequan Yao 《Angewandte Chemie (International ed. in English)》2023,62(51):e202313404
Bicyclo[3.2.1]octadiene compounds and derivatives exist in a number of natural products and bioactive compounds. Nevertheless, catalytic enantioselective protocols for the synthesis of these skeletons have not been disclosed. Herein we reported a palladium-catalyzed asymmetric intramolecular alkene-alkyne coupling of alkyne-tethered cyclopentenes, affording a library of enantionenriched bicyclo[3.2.1]octadienes in excellent yields and enantioselectivities (mostly >99 % ee). Moreover, the products could undergo an unusual iodination-induced 1,2-acyl migration, forming iodinated bicyclo[3.2.1]octadienes with three vicinal stereocenters. The enone and isolated olefin motifs embedded in the products provide useful handles for downstream elaboration. 相似文献
8.
通过萜品油烯和2,6-二氧代戊酸甲酯的de Mayo反应,使[2 + 2]环加成产物 3-6经retro-aldol重排,开环生成取代环己烯7和12。在不同反应介质中对开环产 物进行再环合,并对其反应机理进行研究。在碱性条件下,经分子内Claisen缩合 反应形成螺环化合物;以对甲本碘酸为催化剂的环合,除生成正常的Claisen缩合 产物以外,7和12均发生烯键亲核加成反应,生成具有二环[3.3.1]结构的桥环化合 物9-11和二环[3.2.1]结构的桥环化合物16-18。所得新化合物的化学结构均经IR, ~1H NMR,~(13)C NMR及元素分析予以确定。 相似文献
9.
S. S. Koval’skaya N. G. Kozlov E. A. Dikusar 《Russian Journal of Organic Chemistry》2010,46(10):1493-1502
The reaction of 2-ethynylisoborneol with acetic acid in the presence of boron trifluoride-diethyl ether complex gave 4-ethynylisobornyl
acetate as a result of successive skeletal rearrangements. Under the Kucherov reaction conditions 2-ethynylisoborneol underwent
Meyer—Schuster rearrangement leading to (2-bornylidene)acetaldehyde. The hydration product of 2-ethynylisoborneol, 2-acetylisoborneol,
was obtained by the action of mercury(II) acetate in dioxane under mild conditions. The Nieuwland reaction of 2-ethynylisoborneol
afforded 4-acetylisoborneol acetate. 2-Ethynylisocamphanol in the presence of formic acid gave rise to a mixture of Rupe and
Meyer—Schuster rearrangement products, stereoisomeric 2-(isocamphylidene)acetaldehydes and 2-acetylisocamphene. Mixtures of
acetyl-substituted acetates having a camphane, isocamphane, and bicyclo[3.2.1]octane skeleton were obtained in the reaction
with acetic acid in the presence of BF3-Et2O. Under the Nieuwland reaction conditions 2-ethynylisocamphanol underwent hydration and rearrangement with ring expansion,
yielding a mixture of endo-2-hydroxy-2,6,6,7-tetramethylbicyclo[3.2.1]octan-3-one and the corresponding acetate. 相似文献
10.
The solvolysis rates and products of the 2-exo- norbornyl, bicyclo[3.2.1]oct-8-yl, bicyclo[3.3.1]non-2-yl, bicyclo[3.2.1]oct-6-yl, bicyclo[3.2.1]oct-2-yl and bicyclo[3.2.2]non-6-yl p-toluenesulfonates 10–15 , respectively, are reported. The exo/endo rate ratios for these epimeric secondary tosylates in 80% EtOH varied from 1125 for 11 to 1.6 for 15 . The relative rates varied between 2278 for exo- 10 and 4 ·10?3 for endo- 11 . The hydrolysis products were mainly rearranged alcohols and olefins. The unrearranged alcohols from the exo-tosylates were formed with complete or predominant retention of configuration, whereas those derived from the endo-tosylates were mostly inverted. These results confirm the hypothesis that relative rates, as well as products, are largely determined by the degree of bridging between the cationic center and a dorsal C-atom in the transition state and in the resulting ion pairs. Since bridging is a directed bonding interaction, it is subject to the same angle and conformational strains as ordinary covalent bonds. But bridging requires less geometrical change than the formation of normal bonds and of nonclassical ions. 相似文献
11.
《Tetrahedron》1988,44(13):3931-3944
We describe an efficient synthesis (summarised in Schemes 8 and 10) of an advanced intermediate (34) suitable for the synthesis of gelsemine. The key steps in the synthesis are (i) the Diels-Alder reaction between 1-tetrahydropyranyloxycyclohexa-1,3-diene (10) and methyl β-nitroacrylate (11) giving an adduct (12), in which the chiral centre in the tetrahydropyranyl ring is produced substantially in only one sense, (ii) the rearrangement of a bicyclo [2.2.2] octane (23) into a bicyclo[ 3.2.1] octane (24), where control of which bridge migrates is achieved by a choice of the counterion in the Lewis acid, and (iii) the efficient formation of the quaternary centre by an intramolecular reaction between an allylsilane group and an acyliminium ion (33 → 34). 相似文献
12.
The title compound was synthesized from bicyclo[3.2.1]octenone 1 in six steps and in overall yield 59%. Photochemical rearrangement of β,γ-unsaturated enone 1 is the key step. 相似文献
13.
《Tetrahedron: Asymmetry》2006,17(10):1544-1548
Enantioselective syntheses of bicyclo[3.3.0]octan-3-one, bicyclo[3.2.1]octan-3-one and bicyclo[3.2.1]octan-2-one derivatives were accomplished by employing a chiron based approach, using intramolecular rhodium carbenoid C–H insertion, acid catalysed cyclisation of α-diazo ketone and intramolecular type II carbonyl ene reactions as key steps. 相似文献
14.
E. Lippmaa T. Pehk N. A. Belikova A. A. Bobyleva A. N. Kalinichenko M. D. Ordubadi A. F. Plat 《Magnetic resonance in chemistry : MRC》1976,8(2):74-78
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. 相似文献
15.
Goodell JR Poole JL Beeler AB Aubé J Porco JA 《The Journal of organic chemistry》2011,76(23):9792-9800
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. 相似文献
16.
Jinbao Wu Yuichiro Kadonaga Benke Hong Jin Wang Xiaoguang Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):10995-10999
A concise and enantioselective total synthesis of (+)‐jungermatrobrunin A ( 1 ), which features a unique bicyclo[3.2.1]octene ring skeleton with an unprecedented peroxide bridge, was accomplished in 13 steps by making use of a late‐stage visible‐light‐mediated Schenck ene reaction of (?)‐1α,6α‐diacetoxyjungermannenone C ( 2 ). Along the way, a UV‐light‐induced bicyclo[3.2.1]octene ring rearrangement afforded (+)‐12‐hydroxy‐1α,6α‐diacetoxy‐ent‐kaura‐9(11),16‐dien‐15‐one ( 4 ). These divergent photo‐induced skeletal rearrangements support a possible biogenetic relationship between (+)‐ 1 , (?)‐ 2 , and (+)‐ 4 . 相似文献
17.
Brinker UH Bespokoev AA Reisenauer HP Schreiner PR 《The Journal of organic chemistry》2012,77(8):3800-3807
Bicyclo[3.2.1]oct-6-en-8-ylidene (1) can assume either the conformation of "classical" carbene 1a or that of foiled carbene 1b in which the divalent carbon bends toward the double bond. Oxadiazoline precursors for the generation of 1 were prepared, followed by photochemical and thermal decomposition as well as flash vacuum pyrolysis (FVP) of a tosyl hydrazone sodium salt precursor, to give a number of rearrangement products. Matrix isolation experiments demonstrate the presence of a diazo intermediate and methyl acetate in all photochemical and thermal precursor reactions. The major product from rearrangements of "classical" bridged carbene 1a is bicyclo[3.3.0]octa-1,3-diene as a result of an alkyl shift, while dihydrosemibullvalene formed from a 1,3-C-H insertion. In contrast, thus far unknown strained bicyclo[4.2.0]octa-1,7-diene formed by a vinyl shift in foiled carbene 1b. The experimental results are corroborated by density functional theory (DFT), MP2, and G4 computations. 相似文献
18.
Crina M. Orac 《Tetrahedron letters》2009,50(12):1261-3485
A new and a direct synthetic method for the construction of the bicyclo[3.2.1]octane system is envisioned by assembling cyclic allylsilanes with electron-deficient double bonds in a single step via a formal diastereoselective Lewis acid-promoted [3+2] cycloaddition. 相似文献
19.
An acid-catalyzed Dieckmann-type reaction has been developed to access functionalized bicyclo[3.2.1]alkenediones. This methodology has been successfully extended to more substituted and larger ring homologues, providing a new and efficient route to the core of numerous attractive natural products and their analogues. 相似文献
20.
Synthetic or natural aza-sugars have shown promise as a therapeutic approach to a variety of disease states by acting as transition state mimics to sugar processing enzymes. Although the synthesis of functionalized bicyclo[3.2.1]octanes has been reported, the procedures are relatively long and low yielding. Herein, we report the facile synthesis of polyhydroxylated 2-azabicyclo[3.2.1]octane that can be selectively functionalized. 相似文献