Publications by authors named "Gary L Gard"

N-C bonded (non-bridged) 5-(1,2,3-triazol-1-yl)tetrazoles were synthesized by the Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition click reaction using 5-azido-N-(propan-2-ylidene)-1H-tetrazole (1). For example, the click reaction of 1 in the presence of CuSO(4)5 H(2)O and Na ascorbate at 65-70 degrees C for 48 h in CH(3)CN/H(2)O co-solvent was found to be limited to only terminal alkynes that have electron-withdrawing groups, CF(3)C[triple chemical bond]CH (2 a) and SF(5)C[triple chemical bond]CH (2 b), giving rise to isopropylidene-[5-(4-trifluoromethyl-1,2,3-triazol-1-yl)tetrazol-1-yl]amine (3 a) and isopropylidene-[5-(4-pentafluorosulfanyl-1,2,3-triazol-1-yl)tetrazol-1-yl]amine (3 b) in 47 % and 66 % yields, respectively. When carried out under conditions using CuI and 2,6-lutidine as catalysts at 0 degrees C for 13 h in CHCl(3), the click reaction was versatile toward alkynes even those having electron-donating groups.

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In this study, the effect of fluorine upon the heme-binding ability of the xanthone nucleus was investigated for 3,6-bis-(omega-N,N-diethylaminoamyloxy)-4,5-difluoroxanthone (F2C5). 2-Fluoro-1,3-dimethoxybenzene was prepared by a new, improved method and used to build up the xanthone nucleus. The interaction of F2C5 with heme was investigated by UV-vis, (1)H NMR, and (19)F NMR spectroscopy.

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1-Pentafluorosulfanyl acetylene and its derivatives react with azide or diazomethane giving rise to an SF5-substituted 1,2,3-triazole or pyrazole. The SF5 group increases density remarkably and as a result enhances the detonation performance of the energetic materials relative to the CF3 group.

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The structure of SF(5)OSO(2)F has been investigated using gas-phase electron diffraction and quantum-chemical calculations. It is found to exist primarily in the gauche form (SF(5) group gauche relative to the S-F bond of the SO(2)F group with phi(S-O-S-F = 71(7) degrees ). A small contribution of the trans conformer cannot be excluded.

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The first quaternary salts of pyridine (2), N-methyl imidazole (3), N-propyl triazole (4), and pyridazine (5) that contain the pentafluorosulfanyl (SF(5)) group were prepared and characterized. Neat reactions of the aromatic nitrogen compounds with SF(5)(CF(2))(n)(CH(2))(m)I (n = 2 or 4, m = 2 or 4) gave quaternary iodides 6a-c, 7a-c, 8a, and 9a,b, which were metathesized with LiN(SO(2)CF(3))(2) to form the bis(trifluoromethylsulfonyl)amides 10a-c, 11a-c, 12a, and 13a,b, in high yields. With the exception of the pyridine bis(trifluoromethylsulfonyl)amide salts, the compounds melted or exhibited a T(g) at <0 degrees C.

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Core-ionization energies have been measured for SF(6) (S 2p), SF(5)SF(5) (S 2p), SF(5)Br (S 2p and Br 3d), and SF(5)CF(3) (S 2p and C 1s). These results, together with others that establish correlations between core-ionization energies and Pauling electronegativities, make it possible to assign group electronegativities to SF(5) and CF(3). This method gives electronegativities for these groups comparable to that of bromine, whereas analysis of the effect of these groups on acidity indicates electronegativities comparable to that of fluorine.

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