53946-80-8Relevant academic research and scientific papers
Cycloaddition Reaction of Mesoionic Betaines as an Approach toward Trialkylindoline Alkaloids
Padwa, Albert,Harring, Scott R.,Semones, Mark A.
, p. 44 - 54 (1998)
Intramolecular 1,4-dipolar cycloaddition of an anhydro-4-hydroxy-2-oxo-1,3-thiazium hydroxide across a tethered indole π-bond has been used for the construction of the pentacyclic skeleton of epi-16,17-dihydroeburnamenine. The reaction of 3-ethyl-3-(alkenyl)piperidinones with diketene and trimethylsilyl triflate in benzene at ambient temperature produced annulated pyridones in good yield. The initial reaction involved formation of a N-acetoacetylated amide which was further converted to the pyridone with TMSOTf. The overall process was found to proceed with complete stereospecificity. Treating a sample of 3-ethyl-3-[(E)-4-phenyl-3-butenyl]-2-piperidone with diketene and TMSOTf produced a cycloadduct in 63% yield whose stereochemistry was elucidated by a X-ray crystallographic study. The epimeric Z-isomer produced a different stereoisomer of the annulated dihydropyridone. The mechanism of the annulation involves a TMSOTf induced cyclization followed by proton removal and generation of a cross-conjugated heteroaromatic betaine. This 1,4-dipole undergoes a subsequent intramolecular dipolar cycloaddition across the neighboring π-bond, and the resulting cycloadduct is subsequently converted to the annulated lactam. A related annulation sequence leading to a key intermediate previously utilized in the synthesis of the (±)-vallesamidine has been developed which is based on the intramolecular dipolar cycloaddition of a mesoionic betaine intermediate.
An expedient synthesis of epi-eburnamenine via an intramolecular 1,4-dipolar cycloaddition reaction
Padwa, Albert,Semones, Mark A.
, p. 335 - 338 (2007/10/02)
The intramolecular 1,4-dipolar cycloaddition of an anhydro-4-hydroxy-2-oxo-1,3-thiazium hydroxide across a tethered indole π-bond has been used for the construction of the pentacyclic skeleton of epi-16,17-dihydroeburnamenine.
Synthetic Approach to (+/-)- Vincamine via Cleavage of an α-Diketone Monothioacetal. Alternative Synthesis of (+/-)-Eburnamine, (+/-)-Isoeburnamine, and (+/-)-Eburnamenine
Takano, Seiichi,Hatakeyama, Susumi,Ogasawara, Kunio
, p. 457 - 461 (2007/10/02)
The half ester (8) prepared from cleavage of 2-(1,3-dithian-2-yl)-4-ethoxycarbonyl-4-ethylcyclohexanone (7) has been converted into (+/-)-eburnamine (20), (+/-)-isoeburnamine (21), and (+/-)-eburnamenine (22) by a stereospecific reaction sequence proceeding via the dithian intermediate (16).However an attempted conversion of (16) into (+/-)-vincamine (6) was unsuccessful.
