Sodium sulfide in methanol: a two-in-one reagent for deprotection of silyl and formation of propargyl sulfide
摘要:
A new reagent Na2S/MeOH for silyl deprotection has been developed. The reagent has several advantages which include deprotection of C-TMS, O-TMS, O-TBS, and O-TBDPS, selective removal of C-TMS and O-TMS in the presence of O-TBS and simultaneous desilylation and sulfide formation in one pot. (c) 2015 Elsevier Ltd. All rights reserved.
Highly atom economical uncatalysed and I2-catalysed silylation of phenols, alcohols and carbohydrates, using HMDS under solvent-free reaction conditions (SFRC)
摘要:
An uncatalysed silylation of phenols, regardless on the aggregate state and nature of the substituents with 0.55 equiv of HMDS under solvent-free reaction conditions (SFRC) at room temperature is reported. Sterically hindered phenols, carbohydrates and most of the alcohols additionally required a catalytic amount (up to 2 mol%) of iodine. The reaction protocol is very simple; obtaining a pure product, particularly of uncatalysed reactions, was frequently a completely solvent-free process. (C) 2012 Elsevier Ltd. All rights reserved.
Cobalt Catalysis at the Crossroads: Cobalt-Catalyzed Alder−Ene Reaction versus [2 + 2] Cycloaddition
作者:Gerhard Hilt、Anna Paul、Jonas Treutwein
DOI:10.1021/ol100266u
日期:2010.4.2
The application of bidentate phosphine ligands in cobalt-catalyzed transformations of cyclic alkenes such as cyclopentene and cycloheptene with internal alkynes led to a chemoselective Alder−ene or a [2 + 2] cycloaddition reaction depending on the electronic nature of the alkyne and the bite angle of the ligand used.
The palladium‐catalyzed cyclopropanation of strained alkenes with 3‐trimethylsilyl‐ or 3‐pinacolatoboryl‐1‐arylallyl acetate derivatives is described. This reaction gives cyclopropanation products in good to high yields with a single diastereomer, and the key step is likely to involve the formation of a palladacyclobutene complex from the α‐trimethylsilyl‐ or α‐pinacolatoboryl‐σ‐allylpalladium complex
OSitBuMe₂ and OSiiPr₃ groups, other than the OSiMe₃ group, were successfully substituted. The substitution reaction of enantiopure secondary benzylic silyl ether yielded the corresponding racemic thioether product, which suggested that the reaction of tertiary alkyl, secondary alkyl, benzylic, and propargylic silyl ethers would proceed via a SN1 mechanism.
Cobalt-Catalysed [6+2] Cycloaddition of Internal Alkynes and Terminal Alkenes with Cycloheptatriene
作者:Gerhard Hilt、Anna Paul、Christoph Hengst
DOI:10.1055/s-0029-1216900
日期:2009.10
cobalt-catalysed [6+2] cycloaddition of cycloheptatriene with internal alkynes as well as with terminal alkenes is described. The cycloaddition process is most efficiently catalysed by cobalt dibromide[bis(triisopropylphosphite)] complexes in dichloromethane as the solvent of choice. In the cobalt-catalysed reaction of cycloheptatriene with norbornene an unexpected tricyclic [2+2] cycloaddition product was