PPh<sub>3</sub>⋅HBr-DMSO Mediated Expedient Synthesis of γ-Substituted β,γ-Unsaturated α-Ketomethylthioesters and α-Bromo Enals: Application to the Synthesis of 2-Methylsulfanyl-3(<i>2 H</i>)-furanones
作者:Kanchan Mal、Abhinandan Sharma、Prakas R. Maulik、Indrajit Das
DOI:10.1002/chem.201303755
日期:2014.1.13
An efficient chemoselective general procedure for the synthesis of γ‐substituted β,γ‐unsaturatedα‐ketomethylthioesters from α,β‐unsaturatedketones has been achieved through an unprecedented PPh3⋅HBr‐DMSO mediated oxidative bromination and Kornblum oxidation sequence. The newly developed reagent system serves admirably for the synthesis of α‐bromoenals from enals. Furthermore, AuCl3‐catalyzed efficient
Tandem Chemoselective 1,2-/1,4-Migration of the Thio Group in Keto Thioesters: An Efficient Approach to Substituted Butenolides
作者:Kanchan Mal、Sandip Naskar、Shovan Kumar Sen、Ramalingam Natarajan、Indrajit Das
DOI:10.1002/adsc.201600640
日期:2016.10.20
We report herein an efficient and mechanistically unique tandem chemoselective 1,2‐/1,4‐migration of the thio group in keto thioesters that provides substitutedbutenolides in moderate to excellent yields. Thus, α‐keto thioesters in the presence of stabilized phosphonate carbanions undergo tandem 1,2‐sulfur migration; whereas 1,4‐migration of the thio group has been achieved with the same thioesters
Visible-Light-Activated Divergent Reactivity of Dienones: Dimerization in Neat Conditions and Regioselective <i>E</i> to <i>Z</i> Isomerization in the Solvent
作者:Sandip Naskar、Sabyasachi Roy Chowdhury、Somrita Mondal、Dilip K. Maiti、Sabyashachi Mishra、Indrajit Das
DOI:10.1021/acs.orglett.9b00083
日期:2019.3.15
4-Dienones undergo visible-light-promoted, photocatalyst-free dimerization in neat conditions to provide cyclohexene derivatives stereoselectively through cascade rearrangement pathways, whereas regioselective E → Z isomerization of the more dienophilic doublebond takes place exclusively in nitromethane. On the basis of intermediate isolation and computational DFT studies, the dimerization reaction is proposed
Thermally Activated Geometrical Regioselective <i>E</i>→<i>Z</i> Isomerization‐Enabled Cascade Sequences of Conjugated Dienals: Experimental and DFT Studies
作者:Jayanta Saha、Soumadip Banerjee、Sidhartha Malo、Abhijit Kumar Das、Indrajit Das
DOI:10.1002/chem.202302335
日期:2023.11.13
Thermal isomerization-enabled cascade: Conjugated dienals undergo regioselective 2E,4E→2Z,4E alkene isomerization in a mixture of toluene-alcohol (2 : 1) or only with alcohol at 60–70 °C, which enables subsequent cascade sequences to furnish γ-alkoxybutenolides. Density functional theory (DFT) studies have been employed to shed light on the feasibility of geometrical alkene isomerization and alcohol-assisted
热异构化级联:共轭二醛在甲苯-醇(2:1)混合物中或仅与醇在60-70°C下进行区域选择性2 E,4 E →2 Z,4 E烯烃异构化,这使得后续级联成为可能提供γ-烷氧基丁烯内酯的序列。密度泛函理论(DFT)研究已被用来阐明几何烯烃异构化和醇辅助中继质子转移机制在内酯化之前形成半缩醛中间体的可行性。
A Torquoselective Thermal 6π‐Electrocyclization Approach to 1,4‐Cyclohexadienes via Solvent‐Aided Proton Transfer: Experimental and Theoretical Studies
作者:Jayanta Saha、Soumadip Banerjee、Sidhartha Malo、Abhijit Kumar Das、Indrajit Das
DOI:10.1002/chem.202304009
日期:2024.3.15
1,4-Cyclohexadienes can be directly synthesized by heating (2E,4E,6E)-hexatrienes in a mixture of toluene/MeOH or EtOH (2 : 1) solvents at 90–100 °C. This is done through a torquoselective disrotatory 6π-electrocyclic ring closure followed by a polar protic solvent-assisted proton-transfer process.
1,4-环己二烯可以通过在甲苯/MeOH或EtOH(2:1)溶剂混合物中于90–100°C下加热( 2E , 4E , 6E )-六三烯直接合成。这是通过扭矩选择性旋转 6π-电环闭合,然后是极性质子溶剂辅助的质子转移过程来完成的。