1451255-10-9Relevant academic research and scientific papers
Regiospecific Acylation of Cycloplatinated Complexes: Scope, Limitations, and Mechanistic Implications
Carroll, Jeffrey,Woolard, Hannah G.,Mroz, Robert,Nason, Charles A.,Huo, Shouquan
, p. 1313 - 1322 (2016)
A series of platinum complexes based on the tridentate cyclometalating ligand derivatives 6-arylamino-2,2′-bipyridine, 6-phenoxy-2,2′-bipyridine, 6-phenylthio-2,2′-bipyridine, 6-benzyl-2,2′-bipyridine, and 6-benzoyl-2,2′-bipyridine were synthesized, and their acylation reactions were studied. Acylation of platinum complexes based on 6-(4-R-phenylamino)-2,2′-bipyridine derivatives (R = CH3O, CH3, Cl, COOEt) tolerates both electron-donating and electron-withdrawing substituents on the aryl ring that are para to the amino group. However, platinum complexes based on 6-(3-R′-phenylamino)-2,2′-bipyridine (R′ = CH3, Cl, Br) did not undergo the acylation reaction under the same conditions. Interestingly, the acylation of the platinum complexes based on 6-(3-fluorophenylamino)-2,2′-bipyridine proceeded smoothly, and the results indicate that the acylation is regiospecific and occurs at the metalated carbon. Complexes based on 6-phenoxy-2,2′-bipyridine, 6-phenylthio-2,2′-bipyridine, and 6-benzyl-2,2′-bipyridine are also regioselectively acylated. A cyclometalated platinum complex based on 6-benzoyl-2,2′-bipyridine, where the benzene is more electron deficient than those in other cyclometalated platinum complexes, failed to undergo the acylation reaction. The acylation can be carried out in acetic acid, 1,2-dichloroethane, benzonitrile, and acetonitrile. Other acyl halides such as benzoyl chloride and crotonyl chloride are also effective acylating reagents. On the basis of the fact that the reaction is discouraged by the electron deficiency of the phenyl ring and contrasting results of the acylation of platinum complexes based on 6-(3-R′-phenylamino)-2,2′-bipyridine (R′ = CH3, F, Cl, Br), an unprecedented electrophilic addition-platinum migration-rearomatization cascade mechanism is proposed for the regiospecific acylation reaction.
Reaction of N -isopropyl- N -phenyl-2,2′-bipyridin-6-amine with K2PtCl4: Selective C-H bond activation, C-N bond cleavage, and selective acylation
Carroll, Jeffrey,Gagnier, Joshua P.,Garner, Alexander W.,Moots, Justin G.,Pike, Robert D.,Li, Yumin,Huo, Shouquan
, p. 4828 - 4836 (2013/09/24)
The selective C-H bond activation of N-isopropyl-N-phenyl-2,2′- bipyridin-6-amine promoted by Pt(II) was complicated by the low selectivity of sp2 C-H bond activation in acetonitrile and low yield of sp 3 C-H activation in acetic acid. The use of a base was found to effectively suppress the competing sp3 C-H bond activation in acetonitrile, improving the selectivity of sp2 C-H bond activation from 70% to 99%. In the reaction in acetic acid, the low yield was due to the competing C-N bond cleavage. The use of a base reduced the C-N bond cleavage, but not completely. The reaction of N-tert-butyl-N-phenyl-2,2′-bipyridin- 6-amine with K2PtCl4 in acetic acid produced the cyclometalated complex with complete C-N bond cleavage and its acylated derivative. These results indicated that the C-N bond cleavage might proceed via heterolytic C-N bond dissociation. The acylation following the C-N cleavage in the reaction in acetic acid is regioselective. Further experiments showed that the reaction of N-phenyl-2,2′-bipyridin-6-amine with K 2PtCl4 in acetic acid produced the cyclometalated complex, while the reaction in a mixture of acetic anhydride and acetic acid produced the acylated cyclometalated complex. An X-ray crystal structure study revealed strong intramolecular H bonding in the acylated complexes. The regioselectivity was explained in terms of H bonding and the electron distribution predicted by the DFT calculations.
