161152-65-4Relevant academic research and scientific papers
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
, 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.
Photochemical Reactions of Arenecarboxylic Acid Esters with Electron-Rich Alkenes: 2 + 2 Cycloaddition, Hydrogen Abstraction, and Cycloreversion
Cantrell, Thomas S.,Allen, Andrew C.
, p. 135 - 139 (2007/10/02)
The photochemical reaction of arenecarboxylic acid methyl esters and isopropyl esters with alkenes has been examined and found to afford three types of products: (a) 2-alkoxyoxetanes 3 via a direct 2 + 2 cycloaddition to the substrate alkenes; (b) β,γ-unsaturated ketones 5 via hydrogen abstraction by the carbonyl oxygen of the photoexcited ester from an allylic position of the substrate alkene; and (c) alkoxyalkenes 4, which arise via 2 + 2 cycloreversion of the oxetanes 3.The quantum yields for the formation of the various products generally fell in the range 0.005-0.03, approximately 1 order of magnitude less than those of aryl ketones and aldehydes undergoing similar reactions.
