Search results for "EXPEDIENT ROUTE"
showing 6 items of 6 documents
The synthesis of fluorinated heteroaromatic compounds. Part 1. Five-membered rings with more than two heteroatoms. A review
2005
(2005). THE SYNTHESIS OF FLUORINATED HETEROAROMATIC COMPOUNDS. PART 1. FIVE-MEMBERED RINGS WITH MORE THAN TWO HETEROATOMS. A REVIEW. Organic Preparations and Procedures International: Vol. 37, No. 5, pp. 447-506.
Experimental and DFT studies on competitive heterocyclic rearrangements. part 2: A one-atom side-chain versus the classic three-atom side-chain (Boul…
2007
The experimental investigation of the base-catalyzed rearrangements of 3-acylamino-1,2,4-oxadiazoles evidenced a new reaction pathway which competes with the well-known ring-degenerate Boulton- Katritzky rearrangement (BKR). The new reaction consists of a one-atom side-chain rearrangement that is base-activated, occurs at a higher temperature than the BKR, and irreversibly leads to the corresponding 2-acylamino-1,3,4-oxadiazoles. An extensive DFT study is reported to elucidate the proposed reaction mechanism and to compare the three possible inherent routes: (i) the reversible three-atom side-chain ring-degenerate BKR, (ii) the ring contraction-ring expansion route (RCRE), and (iii) the one…
Designing fluorous domains. Synthesis of a series of pyridinium salts bearing a perfluoroalkylated azole moiety
2006
The synthesis of a series of N-methylpyridinium salts bearing a perfluoroalkylated 1,2,4-oxadiazole or 1,2,4-triazole moiety is reported. X-Ray structures of representative perfluoroalkyl-triazolylpyridine (15) and methyl- pyridinium iodide salt (5a) are reported. Their crystal packing clearly shows segregation between the aromatic and parallel double layer fluorinated regions.
Fluorinated Heterocyclic Compounds. A Photochemical Approach to a Synthesis of Polyfluoroaryl-1,2,4-triazoles.
2005
The reaction of some fluorinated 1,2,4-oxadiazoles in the presence of methylamine or propylamine has been investigated. The irradiation in methanol or acetonitrile leads with acceptable yields to the corresponding fluorinated 1- methyl- or 1-propyl-1,2,4-triazole.
Photochemistry of 1,2,4-oxadiazoles. A DFT study on photoinduced competitive rearrangements of 3-amino- and 3-N-methylamino-5-perfluoroalkyl-1,2,4-ox…
2006
The photoinduced competitive rearrangements of 5-perfluoroalkyl-3-amino(N-alkylamino)-1,2,4-oxadia- zoles have been investigated by DFT calculations and UV-vis spectroscopy. The observed product selectivity depends on the number of hydrogen atoms present in the amino moiety and involves two or three possible routes: (i) ring contraction-ring expansion (RCRE), (ii) internal-cyclization isomerization (ICI), or (iii) C(3)-N(2) migration-nucleophilic attack-cyclization (MNAC). UV absorption and fluorescence spectra of the reactants, and vertical excitation energy values, calculated by time dependent DFT, support the involvement of a neutral singlet excited state in the photoexcitation process. …
Five-to-Six Membered Ring-rearrangements in the Reaction of 5-Perfluoroalkyl-1,2,4-oxadiazoles with Hydrazine and Methylhydrazine
2006
The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine or methylhydrazine as bidentate nucleophiles has been investigated. The reaction occurred through the addition of the bidentate nucleophile to the C(5)-N(4) double bond of the 1,2,4-oxadiazole followed by ring-opening and ring-closure (ANRORC) involving the second nucleophilic site of the reagent. This ring-closure step could involve either the original C(3) of the 1,2,4-oxadiazole (giving a five-to-five membered ring rearrangement) or an additional electrophilic center linked to it (exploiting a five-to-six membered ring rearrangement). An alternative initial nucleophilic attack may involve the additional elec…