The Co_2(CO)_8-mediated intramolecular Pauson-Khand reaction is an efficient approach for constructing polycyclic skeletons. Recently, some of us reported a series of this type reactions involving stericallyhindered e...The Co_2(CO)_8-mediated intramolecular Pauson-Khand reaction is an efficient approach for constructing polycyclic skeletons. Recently, some of us reported a series of this type reactions involving stericallyhindered enynes for synthesizing natural products with reasonable reaction rates and yields. However,the reason for the high reactivity of the reaction remains unclear. We employed density functional theory calculations to clarify the mechanism and reactivity for this reaction. In contrast with chain olefin reactants, CO insertion is considered to be the rate-determining step for the overall Pauson-Khand reaction of cyclooctene derivatives. The reduced activation free energy for the alkene insertion step is attributed to: i) the electron-withdrawing group in close proximity to the C—C triple bond enhancing the reactivity of the alkyne moiety; ii) lower steric hindrance during alkene insertion when using the cyclooctene derivative. The effect of the substituent on the Co_2(CO)_8-mediated intramolecular PausonKhand reaction was then investigated. Internal alkenes exhibit lower reactivity than terminal alkenes because of the steric hindrance introduced by the substituted group. The cis internal alkene exhibits higher reactivity than the trans internal alkene. An ester group in close proximity to the C—C triple bond significantly enhances the reactivity.展开更多
The activity and enantiocontrol ability of the chiral catalysts prepared from spiro di-phosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pau-son-Khand reaction. The results sh...The activity and enantiocontrol ability of the chiral catalysts prepared from spiro di-phosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pau-son-Khand reaction. The results showed that SDP ligands were very effective in Rh-catalyzed Pau-son-Khand reaction, and their complexes with rhodium could convert a variety of 1,6-enyne compounds into bicyclopentone derivatives under CO atmosphere in high yields with good enantioselec-tivities. The SbF6- was found to be a suitable counter anion of the catalyst, and 1,2-dichloroethane was the best choice of the solvent for Pauson-Khand reaction.展开更多
The intermolecular Pauson-Khand reaction between 2-ethynylbenzaldehyde and ethylene promoted by dimethyl sulfide can be utilized to synthesize 2-（2-formylphenyl）cyclopentenone efficiently. This compound and its deri...The intermolecular Pauson-Khand reaction between 2-ethynylbenzaldehyde and ethylene promoted by dimethyl sulfide can be utilized to synthesize 2-（2-formylphenyl）cyclopentenone efficiently. This compound and its deriva- tives undergo a cascade process of Michael addition reaction followed by Henry reaction with nitromethane to con- struct substituted aromatic fused 2,3-dihydroindanones. Furthermore, direct one-pot synthesis of aromatic fused 2,3-dihydroindanones from 2-ethynylbenzaldehyde is achieved.展开更多
In this paper,we report the concise total syntheses of three botryane sesquiterpenoids:dehydrobotrydienal,dehydrobotrydienol,and 10-oxodehydrodihydrobotrydial.The key transformations include tandem Co-tetramethylthiou...In this paper,we report the concise total syntheses of three botryane sesquiterpenoids:dehydrobotrydienal,dehydrobotrydienol,and 10-oxodehydrodihydrobotrydial.The key transformations include tandem Co-tetramethylthiourea-catalyzed Pauson–Khand and 6π-electrocyclization reactions to forge the tricyclic core structure of the botryanes,and further oxidative aromatization and oxidation to complete the total syntheses.展开更多
基金project (Nos. 2018CDYJSY0055, 2018CDXZ0002, 106112017CDJXY220007) supported by the Fundamental Research Funds for the Central Universities (Chongqing University)supported by the National Natural Science Foundation of China (Nos. 21772020 and 21822303)
文摘The Co_2(CO)_8-mediated intramolecular Pauson-Khand reaction is an efficient approach for constructing polycyclic skeletons. Recently, some of us reported a series of this type reactions involving stericallyhindered enynes for synthesizing natural products with reasonable reaction rates and yields. However,the reason for the high reactivity of the reaction remains unclear. We employed density functional theory calculations to clarify the mechanism and reactivity for this reaction. In contrast with chain olefin reactants, CO insertion is considered to be the rate-determining step for the overall Pauson-Khand reaction of cyclooctene derivatives. The reduced activation free energy for the alkene insertion step is attributed to: i) the electron-withdrawing group in close proximity to the C—C triple bond enhancing the reactivity of the alkyne moiety; ii) lower steric hindrance during alkene insertion when using the cyclooctene derivative. The effect of the substituent on the Co_2(CO)_8-mediated intramolecular PausonKhand reaction was then investigated. Internal alkenes exhibit lower reactivity than terminal alkenes because of the steric hindrance introduced by the substituted group. The cis internal alkene exhibits higher reactivity than the trans internal alkene. An ester group in close proximity to the C—C triple bond significantly enhances the reactivity.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 20132010 and 20272026) the Major State Basic Research Development Program (Grant No. G2000077506) the Ministry of Education of China and the Committee of Science and Technology of Tianjin City for financial support.
文摘The activity and enantiocontrol ability of the chiral catalysts prepared from spiro di-phosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pau-son-Khand reaction. The results showed that SDP ligands were very effective in Rh-catalyzed Pau-son-Khand reaction, and their complexes with rhodium could convert a variety of 1,6-enyne compounds into bicyclopentone derivatives under CO atmosphere in high yields with good enantioselec-tivities. The SbF6- was found to be a suitable counter anion of the catalyst, and 1,2-dichloroethane was the best choice of the solvent for Pauson-Khand reaction.
文摘The intermolecular Pauson-Khand reaction between 2-ethynylbenzaldehyde and ethylene promoted by dimethyl sulfide can be utilized to synthesize 2-（2-formylphenyl）cyclopentenone efficiently. This compound and its deriva- tives undergo a cascade process of Michael addition reaction followed by Henry reaction with nitromethane to con- struct substituted aromatic fused 2,3-dihydroindanones. Furthermore, direct one-pot synthesis of aromatic fused 2,3-dihydroindanones from 2-ethynylbenzaldehyde is achieved.
基金supported by the National Natural Science Foundation of China (Nos. 21772008, 21632002 and U1606403)Natural Science Foundation of Guangdong Province (No. 2016A030306011)+1 种基金Shenzhen Basic Research Program (Nos. JCYJ20170818090044432 and JCYJ20160226105337556)Qingdao National Laboratory for Marine Science and Technology (No. LMDBKF201703)
文摘In this paper,we report the concise total syntheses of three botryane sesquiterpenoids:dehydrobotrydienal,dehydrobotrydienol,and 10-oxodehydrodihydrobotrydial.The key transformations include tandem Co-tetramethylthiourea-catalyzed Pauson–Khand and 6π-electrocyclization reactions to forge the tricyclic core structure of the botryanes,and further oxidative aromatization and oxidation to complete the total syntheses.
