Aza-Pauson-Khand reaction

The Pauson-Khand reaction has also been carried out under different conditions, such as the use of chiral ligands, including PuPHOS, CamPHOS, and camphorsultam the use of aldehydes as the carbon monoxide source > the use of solid-supported cobalt catalyst to enhance purification, such as the dry-state adsorption the use of colloidal cobalt nanoparticle and the use of metallic cobalt supported on mesoporous silica prepared by decomposing Co2(CO)8 on mesoporous silica supports (SBA-15 and MCM-41) in the refluxing toluene solution.Other modifications include different promoting methods, such as photo-irradiation, microwave irradiation, molecular sieves, TEMPO,A-oxides, and supercritical fluids. Furthermore, the cycloaddition between allene and carbon monoxide under similar conditions is known as the allenic Pauson-Khand reaction,27,41 jjjg reaction among alkyne, carbodiimide, and CO is referred to as the aza-Pauson-Khand reaction. ... 

The aza-Pauson—Khand reaction ([2+2+1] cycloaddition), where one of the TC-bond-containing components contains a nitrogen atom in place of a carbon atom (e.g., imine in place of alkene), is a powerful strategy for preparing 3-pyrrolin-2-ones and fused 3-pyrrolin-2-ones. One of the earliest... 

Variations on the hydrazulene skeleton have been approached via the Pauson-Khand reaction, several with high regio- and diastereo-selectivity. Pauson s cycloadditions of cycloheptene provided the Brst entries but were limited in scope and efficiency (equation 39).2° Several synthetic equivalents of cyclohep-tenes displaying greater reactivity include 8-oxa- and 8-aza-bicyclo[3.2.1]oct-6-enes (equations 48 and... 

The Pauson-Khand reaction was first applied to the synthesis of several model compounds, e.g., the piperidine derivative 438, as illustrated in Scheme 4.43. The dotted fines show the atoms that are to be connected in the reaction. The desired bicycfic structure was indeed obtained. Of significance was the stereochemistry of the reaction product, where the aza bridge and the proton on C-2 are trans-oiiented as found in the alkaloid. 

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