Pauson-Khand photochemical

Diels-Alder, imino dienophiles, 65, 2 Diels-Alder, intramolecular, 32, 1 Diels-Alder, maleic anhydride, 4, 1 [4 -h 3], 51, 3 of enones, 44, 2 of ketenes, 45, 2 of nitrones and alkenes, 36, 1 Pauson-Khand, 40, 1 photochemical, 44, 2 retro-Diels-Alder reaction, 52, 1 53, 2 [6-h4], 49, 2 [3-h2], 61, 1 Cyclobutanes, synthesis ... 

Fenestranes are compounds of theoretical interest in which the central carbon atom undergoes severe planarization distortion. Reactions sequences involving double intramolecular Pauson-Khand reactions of ene-diynes, or intramolecular Pauson-Khand of dienynes followed by photochemical [2 + 2] cycloaddition, successfully lead to [5.5.5.5]- or [4.5.5.5]fenestrane, respectively [42], For instance, compound 37 was obtained from ene-diyne 36 in moderate yield as a single all-czs stereoisomer [43] (Scheme 18). 

Scheme 4. Photochemically induced, catalytic Pauson-Khand reactions according to Livinghouse.

The Pauson-Khand reaction typically involves the thermal reaction of a Co2(CO)6(/r- -alkyne) with alkene to form a substituted cyclopentenone. A photochemical version of this reaction has been reported.Matrix studies of Co2(CO)6(/r-jj -alkyne) have established that CO-loss occurs from a single position, but that photochemical rearrangement of the Co2(CO)5(/r- j -alkyne) photointermediate readily takes... 

Rhodium, " titanium,and tungsten " complexes have also been used for this reaction. The reaction can be promoted photochemically and the rate is enhanced by the presence of primary amines.Coordinating ligands also accelerate the reaction,polymer-supported promoters have been developed " and there are many possible variations in reaction conditions.The Pauson-Khand reaction has been done under heterogeneous reaction conditions, and with... 

Gordon, C. M., Kiszka, M., Dunkin, I. R., Kerr, W. J., Scott, J. S., Gebicki, J. Elucidating the mechanism of the photochemical Pauson-Khand reaction matrix photochemistry of (phenylacetylene)hexacarbonyldicobalt. J. Organomet. Chem. 1998, 554,147-154. 

Methods for the synthesis of central hydroisoquinolines or pyrrolo-hydroisoquinoHnes of manzamine A can be classified into 11 types of reactions (1) intermolecular Diels-Alder reaction, (2) intramolecular Diels-Alder reaction, (3) photochemical reaction, (4) radical reaction, (5) ionic cyclization, (6) intramolecular Michael reaction, (7) intramolecular Maimich reaction, (8) intramolecular [3 + 2] cycloaddition, (9) intermolecular [3 + 2] cycloaddition, (10) Pauson-Khand reaction, and (11) eneyne metathesis. 

Photochemical intermolecular and intramolecular Pauson-Khand reactions of the allq ne cobalt complexes [RC=CH Co(CO)3 2] with alkenes using a flow microreactor were reported. The reaction of [PhC=CH Co(CO)3 2] with norbornene in a batch reactor led to the product in 32% yield, while the flow reactor resulted in 88% yield. " ... 

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