Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• previous literature. Keywords: asymmetric [3 + 2] annulation; maleimides; Morita–Baylis–Hillman carbonates; multifunctional thiourea-phosphine; organocatalysis; Introduction Highly functionalized cyclopentene derivatives are important subunits in a variety of biologically active molecules and have

• ] have also developed asymmetric [3 + 2] annulations of allenoates to give the corresponding cyclopentene derivatives in good yields with excellent enantioselectivities [37]. On the other hand, some examples of phosphine-catalyzed [3 + 2] annulation of MBH carbonates with electron-deficient alkenes have

• + 2] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentene derivatives bearing three contiguous stereocenters in moderate to excellent yields along with excellent diastereo- and enantioselectivities. Results and Discussion In our previous work, it

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

• Xiufang Ji,
• Zhiming Li,
• Quanrui Wang and
• Andreas Goeke

Beilstein J. Org. Chem. 2012, 8, 650–657, doi:10.3762/bjoc.8.72

• led us to disclose the facial ring opening of a series of cyclobutanones to produce 1,2-disubstituted cyclopentene derivatives with high selectivity. The economic cycloaddition/ring-opening sequence is significant in that it allows a useful functional group to be easily introduced under mild

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• . Disubstituted 1,6-diynes furnished the (Z)-cyclopentylidene derivative 239 stereoselectively [117]. Monosubstituted terminal diyne afforded the cyclopentene derivative 240, while the diterminal 1,6-diyne produced a cyclohexenone derivative 241 (Scheme 43). Cheong and co-workers demonstrated that 1,5-allenynes

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• diradical intermediate of type 17, its lifetime is evidently too short to allow ring-expansion as depicted in Scheme 7. Whether this process might be induced thermally (vinylcyclopropane→cyclopentene rearrangement; [23]) is an open question. Conclusion Although the detailed mechanisms of the

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• medium-sized rings also reacted well to yield interesting seven- or eight-membered ring fused dihydroindolizinones in good yields. Surprisingly, the corresponding cyclopentene or cyclohexene substrates did not afford the corresponding five- or six-membered ring-fused dihydroindolizinones. After 10 h, the

• starting materials were mostly unreacted in the case of cyclohexene substrates and partly decomposed in the case of cyclopentene substrates. This method allows an expedient formal synthesis of indolizidine 167B. Oxycyclizations Transition metal-assisted intramolecular addition of oxygen nucleophiles across

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• ]. An excellent example for such intermolecular selectivity was published a few years ago by Piet et al. (Scheme 10) [38]. They observed a very selective endo 1,3-photocycloaddition across the substituent on the aromatic moiety in the reaction of cyclopentene with a protected isoindoline. This reaction

• to the desired compound via a thermal vinylcyclopropane–cyclopentene rearrangement. All obtained photocycloaddition compounds can be converted into the target by this means. The cyclopropane ring was opened by a Birch-type reduction. Oxidation of the primary alcohol and ozonolysis of the double bond

• cyclopentene with a protected isoindoline. 2,6- and 1,3-addition in intramolecular approach. Linear and angularly fused isomers can be obtained upon intramolecular 1,3-addition. Synthesis of α-cedrene via diastereoselective meta photocycloaddition. Asymmetric meta photocycloaddition introduced by chirality of

Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.0^1,5]dodecenone

• Fuyuhiko Inagaki,
• Naoya Itoh,
• Yujiro Hayashi,
• Yumi Matsui and
• Chisato Mukai

Beilstein J. Org. Chem. 2011, 7, 404–409, doi:10.3762/bjoc.7.52

• provides a new method for the preparation of 9g. The intramolecular Rh(I)-catalyzed PKTR of allenenes is applicable to the more complex substrate as shown in Table 3 [42][43][44]. Exposure of the cyclopentene 10 to the standard conditions in Table 2 did not lead to the desired tricyclo[6.4.0.01,5]dodec-7

Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles

• Franca M. Cordero,
• Carolina Vurchio,
• Stefano Cicchi,
• Armin de Meijere and
• Alberto Brandi

Beilstein J. Org. Chem. 2011, 7, 298–303, doi:10.3762/bjoc.7.39

• of the two diastereomers (E)- and (Z)-19. No trace of the cyclopentene-annelation product was observed in the reaction mixture. In refluxing toluene, the reaction was quite slow and after 15 h in the presence of 5 mol % of catalyst, a considerable amount of starting material still remained. Even

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• ]. Cyclic olefin–alkyne cross-metathesis As already mentioned, EYCM involving internal linear olefins has not been reported. On the other hand, the cross-metathesis of terminal alkynes with the internal carbon–carbon double bond of cyclopentene has been performed in the presence of catalyst II under mild

• reaction demonstrated that ruthenium alkylidene was the active catalytic species (methylidene free conditions). This ring expansion could be extended to fused cycloalkene substrates such as tetrahydroindene and bicyclo[3.2.0]heptenone, both of them featuring a cyclopentene unit to form functionalized

• obtained for EYCM with styrenes. EYCM of terminal olefins with internal borylated alkynes. Synthesis of propenylidene cyclobutane via EYCM. Efficient EYCM with vinyl ethers. From cyclopentene to cyclohepta-1,3-dienes via cyclic olefin-alkyne cross-metathesis. Ring expansion via EYCM from bicyclic olefins

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• in the presence of ruthenium–indenylidene catalyst precursor 1 (5 mol %). A preliminary experiment was carried out in toluene-d8 and monitored by 1H NMR spectroscopy. The RCM of the α,ω-diene occurred readily at 25 °C and a quantitative conversion into cyclopentene derivative 17 was achieved within 1

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• Cope rearrangement and an intramolecular Diels-Alder reaction. The substrate for the Cope rearrangement was prepared by the merger of two cyclopentene units (Scheme 1). First, the addition of chloro compound 8 [18] to aldehyde 9 [19] occurred smoothly using the CrCl3/LAH system, developed by Hiyama et