NMR spectra of 1,3,5-triazines with fluorinated substituents

Brey, Wallace S.; Richardson, David W.; West, John T.

doi:10.1016/j.jfluchem.2004.01.002

Cited by 6 publications

(4 citation statements)

References 17 publications

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“…The peak at 31.2 ppm also appears in the spectrum of the H-DNPs (Supporting Information S11) and comes from the surface carbons that are hydrogenated during the hydrogen treatment. The peak at 38.1 ppm (quaternary 13 C) corresponds to the carbons from the diamond core, consistent with prior studies showing a peak near 37 ppm that is characteristic of the core diamond carbons. − The small peak at 29.6 ppm is assigned to the CH 2 carbon adjacent to the CF 2 group (shown in blue in Figure a) based on the chemical shift of previously reported compounds with mixed CF 2 and CH 2 motifs. − The fluorine atoms couple to this hydrocarbon and split the 13 C peaks, leading to the lower intensity and broadening of the peak at 29.6 ppm. Previous studies have shown that fluorine atoms couple strongly with the adjacent carbon atom through 2-bond coupling, reducing the peak intensity due to the splitting into multiplets.…”

Section: Resultsmentioning

confidence: 99%

Molecular Surface Functionalization of Carbon Materials via Radical-Induced Grafting of Terminal Alkenes

et al. 2019

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Formation of functional monolayers on surfaces of carbon materials is inherently difficult because of the high bond strength of carbon and because common pathways such as SN2 mechanisms cannot take place at surfaces of solid materials. Here, we show that the radical initiators can selectively abstract H atoms from H-terminated carbon surfaces, initiating regioselective grafting of terminal alkenes to surfaces of diamond, glassy carbon, and polymeric carbon dots. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) demonstrate formation of self-terminating organic monolayers linked via the terminal C atom of 1-alkenes. Density functional theory (DFT) calculations suggest that this selectivity is at least partially thermodynamic in origin, as significantly less energy is needed to abstract H atoms from carbon surfaces as compared to typical aliphatic compounds. The regioselectivity favoring binding to the terminal C atom of the reactant alkenes arises from steric hindrance encountered in bond formation at the adjacent carbon atom. Our results demonstrate that carbon surface radical chemistry yields a versatile, selective, and scalable approach to monolayer formation on H-terminated carbon surfaces and provide mechanistic insights into the surface selectivity and regioselectivity of molecular grafting.

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Section: Resultsmentioning

confidence: 99%

Molecular Surface Functionalization of Carbon Materials via Radical-Induced Grafting of Terminal Alkenes

et al. 2019

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“…Similarly, they observed very different gauche and trans 3 J FF in CF 3 CF 2 Cl and CF 3 CF 2 Br. Non-first-order spectra have been observed between CF 2 's in perfluoropropyl groups such as CF 3 CF 2 CF 2 CO 2 H [8] or CF 3 CF 2 CF 2 -substituents on 1,3,5-triazines [9], but the spectra have not been analyzed for the individual coupling constants. Complex higher order spectra are also observed in the middle -CF 2 CF 2 -of HCF 2 CF 2 CF 2 CF 2 CH 2 OH [10].…”

Section: Introductionmentioning

confidence: 99%

Vicinal fluorine–fluorine coupling constants in perfluoropropyl groups

Newmark¹

2009

Journal of Fluorine Chemistry

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“…Taking the advantage that fluorous compounds can be easily analyzed by conventional analytical methods [12], we first conducted a model reaction using F-CDT 5 in deuterinated THF and monitored each reaction step by 1 H NMR analysis. It is noteworthy that THF is a good solvent for coupling reactions with chlorinated triazines.…”

Section: Resultsmentioning

confidence: 99%

Fluorous 2,4‐Dichloro‐1,3,5‐triazine (F‐DCT) as an Amide Coupling Agent

Zhang

2006

QSAR Comb. Sci.

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IntroductionSubstituted 1,3,5-triazines, such as 2-chloro-4,6-dimethoxy-1,3,5-triazine 1 (CDMT) [1], 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) 2 [2], polymer-supported 2,4-dichloro-1,3,5-triazine (PS-DCT) 3 [3], and fluorous CDMT 4 [4], represent an important class of coupling reagents for synthesis of amide bonds [5]. These reagents are derivatives of 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) [6]. Three chlorines of cyanuric chloride have different reactivity. Selective displacement of chlorines with MeOH for example, is performed at 0 °C for the first chlorine, at room temperature for the second one, and at 100 °C for the third one [5]. Commercially available 1,3,5-triazine-based reagents usually employ only one reactive site for coupling reactions. The other two active sites are blocked by alkoxy groups or a fluorous tag. PS-DCT 3 has two chlorines, but only one is reported to be involved in the coupling reaction [3a]. We describe here a new fluorous 2,4-dichloro-1,3,5-triazine (F-DCT) 5 which has one fluorous chain and two active sites for amide coupling reactions.A decade ago, fluorous technology was first introduced as a new phase-tagging strategy for biphasic catalysis [7]. The scope of fluorous chemistry has been well advanced since then and now it covers many aspects of organic synthesis [8]. A series of fluorous catalysts, reagents, scavengers, and protecting groups have been developed for solution-phase parallel and combinatorial synthesis of small molecules, peptides, and oligosaccharides ResultsThe preparation of 5 was accomplished by modifying literature procedures [11] using one equiv of 3-(perfluorooctyl)propanol, 1.05 equiv of cyanuric chloride, and 2,4,6-collidine as a base. The reaction was conducted in benzotrifluride (BTF) at 25 °C for 10 h. After filtration to remove the salt, the concentrated crude product was crystallized from hexanes to give 5 in 60% as a white solid. Crude product can also be purified by flash column chromatography with normal silica gel. Compound 5 is slowly decomposed if it is not stored under nitrogen in a sealed bottle. Its purity can be easily determined by GC analysis.Taking advantage of the fact that fluorous compounds can be easily analyzed by conventional analytical methods [12], we first conducted a model reaction using F-CDT 5 in deuterinated THF and monitored each reaction step by 1 H NMR analysis. It is noteworthy that THF is a good solvent for coupling reactions with chlorinated triazines. Other solvents such as CH 2 Cl 2 may cause demethylation of N-methylmorpholine (NMM)-triazine complex [13]. At the first step, one equiv of 5 and two equiv of p-bromobenzoic acid was mixed in THF-d. Analysis of the mixture showed no reaction occurred at room temperature (Figure 1a). At the second step, 2.1 equiv of NMM was added and a small amount of white precipitate (presumably NMM-HCl salt) was generated immediately at room temperature. Chemical shift changes of aromatic protons indicated the formation of activated acid 6 (Fi...

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NMR spectra of 1,3,5-triazines with fluorinated substituents

Cited by 6 publications

References 17 publications

Molecular Surface Functionalization of Carbon Materials via Radical-Induced Grafting of Terminal Alkenes

Molecular Surface Functionalization of Carbon Materials via Radical-Induced Grafting of Terminal Alkenes

Vicinal fluorine–fluorine coupling constants in perfluoropropyl groups

Fluorous 2,4‐Dichloro‐1,3,5‐triazine (F‐DCT) as an Amide Coupling Agent

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