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
Transition‐Metal‐Free Reduction of
<i>α</i>
‐Keto Thioesters with Hydrosilanes at Room Temperature: Divergent Synthesis through Reagent‐Controlled Chemoselectivities
作者:Rajib Maity、Bhanuranjan Das、Indrajit Das
DOI:10.1002/adsc.201900222
日期:2019.5.14
acid as a promoter can be used for the reagent‐controlled chemoselective reduction at room temperature of conjugated C=C bond, enone moiety, or the carbonyl of (β,γ‐unsaturated) α‐keto thioesters, providing facile access to β,γ‐saturatedα‐keto thioesters, α‐hydroxy thioesters, or silyl ethers. The reaction pathway and the chemoselectivity can be fine‐tuned through the judicious choice of the hydrosilane
氢硅烷与布朗斯台德酸或路易斯酸作为促进剂的组合可用于在室温下进行试剂控制的化学选择还原反应,以还原共轭C = C键,烯酮部分或(β,γ-不饱和)α-酮的羰基硫酯,可轻松获得β,γ-饱和的α-酮硫代酯,α-羟基硫代酯或甲硅烷基醚。可以通过明智地选择氢化硅烷或反应条件来微调反应途径和化学选择性。该反应可耐受包括不稳定的硫酯在内的各种官能团,并且通常以中等至极好的收率获得产物。不对称硫醚也可以使用PMHS和催化性B(C 6 F 5)3合成通过两个羰基的还原性脱氧。β,γ-不饱和α-羟基硫代酯和β,γ-饱和α-酮硫代酯的饱和α-酮酰胺的胺介导和无偶联剂的合成突出了其适用性。
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
Copper(II)-Catalyzed Reactions of α-Keto Thioesters with Azides via C–C and C–S Bond Cleavages: Synthesis of <i>N</i>-Acylureas and Amides
作者:Rajib Maity、Sandip Naskar、Indrajit Das
DOI:10.1021/acs.joc.7b03054
日期:2018.2.16
Cu(II)-catalyzed reaction of α-keto thioesters with trimethylsilyl azide (TMSN3) proceeds with the transformation of the thioester group into urea through C–C and C–S bond cleavages, constituting a practical and straightforward synthesis of N-acylureas. When diphenyl phosphoryl azide (DPPA) is used instead as the azide source in an aqueous environment, primary amides are formed via substitution of
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