58001-94-8Relevant articles and documents
Method for preparing single-configuration C-2-position-monosubstituted norbornene derivative
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, (2021/07/01)
The invention discloses a method for preparing a single-configuration C-2-position-monosubstituted norbornene derivative. The method comprises the following steps of: firstly, preparing exo-isomer enriched exo-isomer mixed 5-norbornene-2-carboxylic ester by taking commercial exo-isomer/endoisomer mixed 5-norbornene-2-carboxylic acid and large-steric-hindrance monohydric alcohol as raw materials; separating 5-norbornene-2-carboxylate with a single configuration through common column chromatography separation or fractionation; and finally, preparing the C-2-position-monosubstituted norbornene derivative with the single configuration from the separated 5-norbornene-2-carboxylate with the single configuration. The raw materials used in the invention are easy to obtain, the preparation process is simple, and the C-2-position-monosubstituted norbornene derivative with high purity (greater than 98%) and single configuration can be obtained.
Improving the efficiency of the Diels-Alder process by using flow chemistry and zeolite catalysis
Seghers,Protasova,Mullens,Thybaut,Stevens
supporting information, p. 237 - 248 (2017/08/14)
The industrial application of the Diels-Alder reaction for the atom-efficient synthesis of (hetero)cyclic compounds constitutes an important challenge. Safety and purity concerns, related to the instability of the polymerization prone diene and/or dienophile, limit the scalability of the production capacity of Diels-Alder products in a batch mode. To tackle these problems, the use of a high-pressure continuous microreactor process was considered. In order to increase the yields and the selectivity towards the endo-isomer, commercially available zeolites were used as a heterogeneous catalyst in a microscale packed bed reactor. As a result, a high conversion (≥95%) and endo-selectivity (89:11) were reached for the reaction of cyclopentadiene and methyl acrylate, using a 1:1 stoichiometry. A throughput of 0.87 g h-1 during at least 7 h was reached, corresponding to a 3.5 times higher catalytic productivity and a 14 times higher production of Diels-Alder adducts in comparison to the heterogeneous lab-scale batch process. Catalyst deactivation was hardly observed within this time frame. Moreover, complete regeneration of the zeolite was demonstrated using a straightforward calcination procedure.
Ruthenium Lewis Acid-Catalyzed Asymmetric Diels–Alder Reactions: Reverse-Face Selectivity for α,β-Unsaturated Aldehydes and Ketones
Thamapipol, Sirinporn,Ludwig, Bettina,Besnard, Céline,Saudan, Christophe,Kündig, E. Peter
, p. 774 - 789 (2016/10/17)
Acrolein, methacrolein, methyl vinyl ketone, ethyl vinyl ketone, 3-methyl-3-en-2-one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron-poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to solid-state structures and to the facial selectivities of catalytic asymmetric Diels–Alder reactions with cyclopentadiene. X-Ray structures of four Ru-enal and Ru-enone complexes show the α,β-unsaturated C=O compounds to adopt an anti-s-trans conformation. In solution, enals assume both anti-s-trans and anti-s-cis conformations. An additional conformation, syn-s-trans, is present in enone complexes. Enantioface selectivity in the cycloaddition reactions differs for enals and enones. Reaction products indicate enals to react exclusively in the anti-s-trans conformation, whereas with enones, the major product results from the syn-s-trans conformation. The alkene in s-cis conformations, while present in solution, is shielded and cannot undergo cycloaddition. A syn-s-trans conformation is found in the solid state of the bulky 6,6-dimethyl cyclohexanone-Ru(II) complex. The X-ray structure of divinyl ketone is unique in that the Ru(II) center binds the enone via a η2bond to one of the alkene moieties. In solution, coordination to Ru–C=O oxygen is adopted. A comparison of facial preference is also made to the corresponding indenyl Lewis acids.
