29214-60-6Relevant articles and documents
Asymmetric Aza-Wacker-Type Cyclization of N-Ts Hydrazine-Tethered Tetrasubstituted Olefins: Synthesis of Pyrazolines Bearing One Quaternary or Two Vicinal Stereocenters
Kou, Xuezhen,Shao, Qihang,Ye, Chenghao,Yang, Guoqiang,Zhang, Wanbin
supporting information, p. 7587 - 7597 (2018/06/04)
We have developed an asymmetric aza-Wacker-type cyclization of N-Ts hydrazine-tethered tetrasubstituted olefins, affording optically active pyrazolines bearing chiral tetrasubstituted carbon stereocenters. This reaction is tolerant to a broad range of substrates under mild reaction conditions, giving the desired chiral products with high enantioselectivities. Generation of two vicinal stereocenters on the C=C double bonds was also achieved with high selectivities, a process which has been rarely studied for Wacker-type reactions. A mechanistic study revealed that this aza-Wacker-type cyclization undergoes a syn-aminopalladation process. It was also found that for substrates bearing two linear alkyl substituents on the outer carbon atom of the olefin, both of which are larger than a methyl group, the alkyl substituent that is cis to the intranucleophilic group participates more readily in β-hydride elimination. When one of the two alkyl substituents on the outer carbon atom of the olefin is a methyl group, β-hydride elimination proceeds selectively at the methylene side, thus both diastereomers can be prepared via switching the configuration of the olefin. Furthermore, the product can be converted to a pharmaceutical compound in high yields over three steps.
Nano-K2CO3: Preparation, characterization and evaluation of reactive activities
Li, Jun-Zhang,Fan, Shi-Ming,Sun, Xuan-Fei,Liu, Shouxin
, p. 1865 - 1869 (2016/01/20)
A novel base, nano-K2CO3, was easily prepared by ultrafine wet milling. The surface properties and the reactive activities of nano-K2CO3 were characterized. It was found that such a base showed higher basicity than normal K2CO3 and could replace sodium (or potassium) alkoxide to carry out monoalkylation and oximation of active methylene compounds. The nano-K2CO3 could be regenarated and reused 10 times without loss of its reactive activity.
Manganese(III)-promoted tandem oxidation and cyclization of β-keto ester derivatives of terpenoids
Li, Zhilong,Jung, Heejung,Park, Mira,Lah, Myoung Soo,Koo, Sangho
supporting information; experimental part, p. 1913 - 1917 (2011/10/08)
A new type of terpenoid cyclization directed by a β-keto ester moiety has been developed, which proceeded by manganese(III)-initiated oxidation of the β-keto ester, followed by an intramolecular hetero Diels-Alder reaction with the terpenoid chain. This reaction produces polycyclic dihydropyrans in high yields and stereoselectivities under mild conditions. Copyright
