Abstract
A convenient carbonylative approach to 2-oxazolidinone derivatives carried out using an ionic liquid (1-ethyl-3-methylimidazolium ethyl sulfate, EmimEtSO4) as the solvent is presented. It is based on the sequential concatenation of two catalytic cycles, both catalyzed by the same metal species (auto-tandem catalysis): the first cycle corresponds to the oxidative monoaminocarbonylation of the triple bond of propargylic amines to give the corresponding 2-ynamide intermediates, while the second one involves the cyclocarbonylation of the latter to yield 2-(2-oxooxazolidin-5-ylidene)-acetamides. Reactions are carried out using a simple catalytic system consisting of PdI2 in conjunction with an excess of KI, and the catalyst/solvent system could be recycled several times without appreciable loss of activity after extraction of the organic product with Et2O.
Highlights
IntroductionIn which a catalytic cycle is concatenated to another eventually leading to the final produc1t,
Cascade catalysis, in which a catalytic cycle is concatenated to another eventually leading to the final produc1t
We report on the direct synthesis of 2-oxazolidinone derivatives through an auto-Mtaonledcuelems 20c16a,t2a1l,y89s7is process consisting of the concatenation of two carbonylative catalyt2icofc8ycles, bthoethioctnaaintcadlleIiynqmzutehciddaistba1wly-yeosttrihhksye,plws-r3aoe-mcmreesepesctocharoyttnalosilnmiystttiiihdcneagsdzyooisrflteitecuhmtmesyc(eoPntntdhhcIyae2stleiissnnuaocltffioao2ntn-eojuxo(naEf zcmtowtilioiomdnciEnawtorSbniOtoehn4dy)aelnaaristveivaaxentcivecuasenstsactolohyfnrtKiovcuIecg)ny,htcpilaoeensnr,faaoblurostmtooh-levdenint
Summary
In which a catalytic cycle is concatenated to another eventually leading to the final produc1t,. Our first experiment was carried out using N-benzyl-2-methylbut-3-yn-2-amine (1a) as the substrate This compound was allowed to react with CO, morpholine (2a), O2, and water in the presence of the catalytic system PdI2/KI under the following conditions: PdI2/KI/1a/2a/H2O molar ratio = 1:10:50:250:250, T = 100 ̋C, P(CO) = 16 atm, P(air) = 4 atm, EmimEtSO4 as the solvent (0.5 mmol of 1a per mL of solvent) (Table 1, entry 1, run 1). The yield turned out to be lower using only 2 equiv of 2a instead of 5 (total yield = 55%) These results confirmed the possibility to carry out the auto-tandem catalysis process leading to oxazolidinones 3 in an ionic liquid (IL) as unconventional solvent. Good yields of the corresponding 2-(2-oxooxazolidin-5-ylidene)acetamides 3 were obtained (69%–76%), and the PdI2/KI/EmimEtSO4 system could be conveniently recycled up to six times without loss of activity
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