Bicyclic Alkenes Research Articles

ChemInform Abstract: Diastereoselective [3 + 2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes Through Cobalt‐Catalyzed C—H Activation and Intramolecular Nucleophilic Addition.

A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group. Transition-metal-catalyzed C-H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C-H bond cleavage may be the rate-limiting step.

An easy access to fused chromanones via rhodium catalyzed oxidative coupling of salicylaldehydes with heterobicyclic olefins

Herein we describe a detailed study on the rhodium catalyzed oxidative coupling of salicylaldehydes with heterobicyclic olefins such as diazabicyclic olefins and urea-derived bicyclic olefins. The developed method provides an ideal route to fused chromanone systems in a single synthetic step. Moreover, the scope of this methodology was extended to different oxa/aza-bridged bicyclic urea derivatives.

Back Cover: Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt‐Catalyzed C−H Activation and Intramolecular Nucleophilic Addition (Angew. Chem. Int. Ed. 13/2016)

Back Cover: Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt‐Catalyzed C−H Activation and Intramolecular Nucleophilic Addition (Angew. Chem. Int. Ed. 13/2016)

Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt‐Catalyzed C−H Activation and Intramolecular Nucleophilic Addition

AbstractA highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt‐catalyzed C−H activation and intramolecular nucleophilic addition to the amide functional group. Transition‐metal‐catalyzed C−H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C−H bond cleavage may be the rate‐limiting step.

Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt-Catalyzed C-H Activation and Intramolecular Nucleophilic Addition.

A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group. Transition-metal-catalyzed C-H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C-H bond cleavage may be the rate-limiting step.

Gold‐Mediated Isomerization of ­Cyclooctyne to Ring Fused Olefinic Bicycles

AbstractIsomerization reactions of cyclooctyne mediated by N‐heterocyclic carbene supported gold(I) leading to ring‐contraction and the formation of 5/5‐fused bicyclic alkenes have been observed. Isolation and complete characterization, including X‐ray structural data of the cationic gold(I) complexes featuring the precursor alkyne and the product alkenes are also described.

Progress in Transition Metal-Catalyzed Asymmetric Ring-Opening Reactions of Oxa(Aza)bicyclic Alkenes with Carbanion Nucleophiles

The recent progress in transition metal-catalyzed asymmetric ring-opening reactions of oxa(aza)bicyclic alkenes with carbanion nucleophiles was reviewed focused on the influence of the types of transition metal catalysts, carbanion nucleophiles, ligands, the structures of oxa(aza)bicyclic alkenes, solvents and additives on the asymmetric ring-opening reactions. Moreover, the parties of possible mechanisms for the asymmetric ring-opening reactions were also discussed.

Cobalt-Catalyzed Allylation of Heterobicyclic Alkenes: Ligand-Induced Divergent Reactivities.

The allylation of heterobicyclic alkenes is presented for the first time. By using an inexpensive cobalt salt as the catalyst and easy-to-handle potassium allyltrifluoroborate as the reagent, an unprecedented formal hydroallylation of the bicyclic alkenes is realized in high efficiency. When a chiral cobalt/bis(phosphine) complex is used instead, the alternative ring-opening products can be obtained in high yield and excellent enantioselectivity.

Cobalt‐Catalyzed Allylation of Heterobicyclic Alkenes: Ligand‐Induced Divergent Reactivities

AbstractThe allylation of heterobicyclic alkenes is presented for the first time. By using an inexpensive cobalt salt as the catalyst and easy‐to‐handle potassium allyltrifluoroborate as the reagent, an unprecedented formal hydroallylation of the bicyclic alkenes is realized in high efficiency. When a chiral cobalt/bis(phosphine) complex is used instead, the alternative ring‐opening products can be obtained in high yield and excellent enantioselectivity.

Studies directed towards the total synthesis of polyether antibiotic ionomycin: asymmetric synthesis of fragments C(24)–C(32) and C(1)–C(23)

A convergent and stereoselective approach for the synthesis of C1–C23 and C24–C32 segments of polyether antibiotic, ionomycin has been achieved. The key steps involved in this approach are the elaboration of two advanced fragments from a common precursor using enzymatic desymmetrization to create two methyl chiral centers, desymmetrization of the bicyclic olefin to introduce two methyl and two hydroxyl chiral centers, the use of Evans auxiliary to introduce another methyl group and the creation of four chiral centers in bis-tetrahydrofuran ring by Sharpless asymmetric epoxidation and the regioselective opening of epoxide with methyl sulphone. The coupling of C11–C16 with C17–C23 was achieved through a Julia-Kocienski olefination and directed Aldol reaction. Oxidation of C9 alcohol facilitates the coupling of C10–C23 with C1–C9.

ChemInform Abstract: Copper(I)—Taniaphos Catalyzed Enantiodivergent Hydroboration of Bicyclic Alkenes.

AbstractCopper‐catalyzed enantiodivergent hydroboration of bicyclic alkenes is achieved using the same chiral ligand (TPO) but different boron sources.

ChemInform Abstract: Copper‐Catalyzed Stereoselective Aminoboration of Bicyclic Alkenes.

AbstractA copper‐catalyzed, exo‐selective aminoboration of bicyclic alkenes, including oxa‐ and azabenzonorbornadienes, is developed.

ChemInform Abstract: Ruthenium‐Catalyzed Asymmetric [2 + 2] Cycloadditions Between Chiral Acyl Camphorsultam‐Substituted Alkynes and Bicyclic Alkenes.

Ruthenium-catalyzed asymmetric [2 + 2] cycloadditions between chiral acyl camphorsultam-functionalized alkynes and bicyclic alkenes were examined, providing adducts with complete exo stereoselectivity in good overall yield and enantioselectivity (up to 99% and 166:1, respectively), as well as appreciable diastereoselectivity (up to 163:1). The diastereoselectivity showed dependence on the solvent and temperature, as well as on the substitution pattern of the reacting alkyne and bicyclic alkene components. In general, higher diastereoselectivities were observed for reactions conducted in ethereal solvents and at lower temperatures between N-propynoyl camphorsultams and bicyclic alkenes.

Photochemisch induzierte C–C-Verknüpfungen zwischen einem Mangan-koordinierten Pentadienylliganden und Acetylen

Abstract Irradiation of tricarbonyl(η5-2,4-dimethyl-2,4-pentadien-1-yl)manganese (1) in tetrahydrofuran (THF) at 208 K affords the carmine solvent complex dicarbonyl(η5-2,4-dimethyl-2,4-pentadien-1-yl)(THF)manganese (2). Complex 2 thermally reacts with acetylene (3) to give tricarbonyl(η3:2-1,3-dimethyl-bicyclo[3.3.1]-3,6-nonadien-2-yl)manganese (4) and dicarbonyl(5-7,10-13-η-6,8-dimethyl-1,3,5,8,10,12-tridecahexaen-5-yl)manganese (5). The crystal structure of complex 4 was determined at room temperature [triclinic space group P 1 ¯ , $P\bar 1,$ a =7.6891(9), b =8.3860(8), c =10.5252(13) Å, α =93.000(9)°, β =93.390(10)°, γ = 108.032(8)°, V =642.43(13) Å3]. The manganese atom is trigonal-bipyramidally coordinated by three carbonyl ligands, one ethenylic and one allylic fragment. Consequently, the bicyclic olefin ligand 1,3-dimethyl-bicyclo[3.3.1]-3,6-nonadiene coordinates the manganese atom in a η3:2 mode. The constitution of complex 5 was deduced from IR data, elemental analysis, and 1H NMR spectra. For the formation of complexes 4 and 5, a reaction mechanism is proposed.

Copper(I)-taniaphos catalyzed enantiodivergent hydroboration of bicyclic alkenes.

In this study, highly enantioselective copper(I)-catalyzed hydroboration of bicyclic alkenes is reported. Using a copper-taniaphos complex, excellent enantioselectivities up to >99% ee were obtained for bicyclic alkenes including oxa- and azabicyclic alkenes. Furthermore, copper-catalyzed enantiodivergent hydroboration methods with the same chiral ligand-copper precursors were developed using different boron sources based on alternative mechanistic pathways.

Infrared matrix isolation and theoretical studies of reactions of ozone with bicyclic alkenes: α-pinene, norbornene, and norbornadiene.

The reactions of ozone with three bicyclic alkenes, α-pinene, norbornene, and norbornadiene, were studied by low-temperature (14 K), argon matrix isolation infrared spectroscopy including (18)O isotope-labeling studies. Theoretical calculations of some of the proposed reaction intermediates and products were carried out using the Gaussian 09 suite of programs, applying density functional theory (DFT), the B3LYP functional, and the 6-311G++(d,2p) basis set. In the α-pinene/ozone system, the thermal reaction between α-pinene and ozone was too slow to observe under the twin-jet or merged-jet deposition conditions of these experiments. However, red light (λ ≥ 600 nm) irradiation of the argon matrixes containing α-pinene and ozone caused new infrared peaks to appear that could be readily assigned to reaction products of α-pinene with O((3)P) resulting from ozone photolysis: α-pinene oxide (with an epoxide ring) and two isomeric ketones. Norbornene and norbornadiene were both found to react with ozone in the gas phase during twin-jet or merged-jet deposition of these mixtures with argon. New peaks observed in the infrared spectra were assigned to the primary ozonides, Criegee intermediates, and secondary ozonides of norbornene and norbornadiene, indicating that the bulk of these reactions proceeded via the "classic" Criegee mechanism for ozonolysis of alkenes. Calculated infrared frequencies and molecular energies support these conclusions. Ultraviolet irradiation of these mixtures resulted in complete decomposition of the early intermediates and the formation of acids, aldehydes, alcohols, carbon dioxide, and carbon monoxide. In any case, no evidence for "unusual" chemistry, prompted by the bicyclic nature of the reactants, was observed.

Stereoselective hydroacylation of bicyclic alkenes with 2-hydroxybenzaldehydes catalyzed by hydroxoiridium/diene complexes.

A hydroxoiridium complex coordinated with 1,5-cyclooctadiene efficiently catalyzed the hydroacylation of bicyclic alkenes with 2-hydroxybenzaldehyde and its derivatives in high yields with high stereoselectivity.

Copper-catalyzed stereoselective aminoboration of bicyclic alkenes.

A copper-catalyzed aminoboration of bicyclic alkenes, including oxa- and azabenzonorbornadienes, has been developed. With this method, amine and boron moieties are simultaneously introduced at an olefin with exo selectivity. Subsequent stereospecific transformations of the boryl group can provide oxygen- and nitrogen-rich cyclic molecules with motifs that may be found in natural products or pharmaceutically active compounds. Moreover, a catalytic asymmetric variant of this transformation was realized by using a copper complex with a chiral bisphosphine ligand, namely (R,R)-Ph-BPE.

Copper‐Catalyzed Stereoselective Aminoboration of Bicyclic Alkenes

AbstractA copper‐catalyzed aminoboration of bicyclic alkenes, including oxa‐ and azabenzonorbornadienes, has been developed. With this method, amine and boron moieties are simultaneously introduced at an olefin with exo selectivity. Subsequent stereospecific transformations of the boryl group can provide oxygen‐ and nitrogen‐rich cyclic molecules with motifs that may be found in natural products or pharmaceutically active compounds. Moreover, a catalytic asymmetric variant of this transformation was realized by using a copper complex with a chiral bisphosphine ligand, namely (R,R)‐Ph‐BPE.

ChemInform Abstract: The Use of Silyl Ketene Acetals and Enol Ethers in the Catalytic Enantioselective Alkylative Ring Opening of Oxa/Aza Bicyclic Alkenes.

AbstractSeveral further transformations of the primary reaction products are described.