Preparation of Chiral 5,6-trans-Disubstituted Phenanthrolines from Phenanthroline-5,6-epoxide

Schoffers, Elke; Tran, Son Duc; Mace, Kristen

doi:10.3987/com-02-9689

Cited by 10 publications

(7 citation statements)

References 7 publications

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“…This step provides the free amine whose enhanced nucleophilicity is required for the subsequent ring opening of epoxide 3 . A range of activators such as Lewis acids or lithium salts − was then tested to carry out the aminolysis of 3 by 8 . We first evaluated LiClO 4 as a catalyst, because this compound had already been used successfully in the first approach to the synthesis of PhenHDO3A (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

Auto-Assembling of Ditopic Macrocyclic Lanthanide Chelates with Transition-Metal Ions. Rigid Multimetallic High Relaxivity Contrast Agents for Magnetic Resonance Imaging

et al. 2006

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PhenHDO3A is a ditopic ligand featuring a tetraazacyclododecane unit substituted by three acetate arms and one 6-hydroxy-5,6-dihydro-1,10-phenanthroline group (PhenHDO3A = rel-10-[(5R,6R)-5,6-dihydro-6-hydroxy-1,10-phenantholin-5-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid). This ligand was specially designed so as to obtain highly stable heteropolymetallic assemblies. PhenHDO3A has been prepared starting from phenanthroline epoxide and either a triprotected tetraazacyclododecane or tert-butyl triester of N,N',N' '-tetraazacyclododecane-triacetic acid. The latter yields PhenHDO3A in a single step. PhenHDO3A forms kinetically stable lanthanide complexes (acid-catalyzed kinetic constant kH = (1.2 +/- 0.2) x 10(-3) s(-1) M(-1)) whose solution structure has been deduced from a quantitative analysis of the paramagnetic shifts and the longitudinal relaxation times of the proton nuclei of YbPhenHDO3A. The alcohol group of the dihydro-phenanthroline unit remains coordinated to the encapsulated metal ion despite the steric crowding brought about by this group. Furthermore, the complexes are monohydrated, as shown by luminescence lifetime measurements on EuPhenHDO3A solutions. Relaxivity titrations at 20 MHz clearly indicate that the phenanthroline unit of GdPhenHDO3A is available for the spontaneous formation of highly stable tris complexes with the Fe2+ and Ni2+ ions. The water-exchange times and the rotational correlation times of GdPhenHDO3A and Fe(GdPhenHDO3A)32+ have been deduced from variable temperature 17O NMR studies and from nuclear relaxation dispersion curves. Despite rather slow water-exchange rates (taum0 = 1.0-1.2 x 10(-6) s), relaxivity gains of 90% have been observed upon the formation of the heterometallic tris complexes. The latter rotate about four times more slowly (taur0= 398 ps) than the monomeric unit (taur0 = 105 ps) and their relaxivity is, accordingly, twice as high. The relaxivity of the tris complexes between 10 and 50 MHz is comparable to relaxivities reported for Gd3+-containing dendrimers of much higher molecular weights. The high relaxivity of the tris-PhenHDO3A lanthanide complexes is attributed to their internal rigidity.

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Section: Resultsmentioning

confidence: 99%

Auto-Assembling of Ditopic Macrocyclic Lanthanide Chelates with Transition-Metal Ions. Rigid Multimetallic High Relaxivity Contrast Agents for Magnetic Resonance Imaging

et al. 2006

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“…We previously found that magnesium perchlorate and alumina catalyzed the ring‐opening of epoxide 1 with nitrogen nucleophiles, whereas oxygen nucleophiles required a stronger Lewis acid, ytterbium(III) triflate 48, 51. Reactions proceeded with a variety of alcohols in 81–99% yield but attempts to use phenol were unsuccessful.…”

Section: Resultsmentioning

confidence: 99%

“…B‐ring‐modified 5,6‐dihydro‐1,10‐phenanthrolines have unique structural properties and can display axial chirality and/or central chirality; the latter typically referring to the presence of one or more stereogenic centers in the absence of an axis or plane 45–47. A few derivatives were recently prepared via epoxide‐opening with oxygen‐ and nitrogen nucleophiles,48–51 and via intramolecular Ullmann coupling of two ethyl‐bridged pyridine rings 52. Until now no optically active cis ‐5,6‐dihydro derivatives that contain axial and central chirality have been reported.…”

Section: Introductionmentioning

confidence: 99%

First isolation of disubstituted cis‐5,6‐dihydro‐1,10‐phenanthrolines. lipase‐mediated resolution of cis‐ and trans‐phenoxy alcohol isomers and assignment of absolute stereochemistry via cd and nmr spectroscopy

et al. 2012

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5,6-Dihydro-1,10-phenanthrolines can display axial and central chirality. In conjunction with the ligating properties of the diimino moiety, this class of compounds is of great interest to applications in supramolecular chemistry. We report the first preparation of cis-5,6-dihydro-1,10-phenanthroline derivatives by reacting triphenyl borate with the corresponding epoxide precursor. We found that solvent and temperature choice determined the stereoselectivity of the epoxide opening giving rise to the cis (14:1 dr) or trans (99:1 dr) product. Racemates of each stereoisomeric mixture, cis- and trans-phenoxy alcohol, were separated via highly enantioselective transesterifications with lipase PSCI from Burkholderia cepacia (97% ee, E > 200). Stereochemical assignments were carried out using CD and X-ray analyses in conjunction with NMR studies of α-methoxy-α-(trifluoromethyl)phenylacetic acid and α-methoxyphenylacetic acid esters.

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“…Ring-opening of 1,10-phenanthroline-5,6-epoxide with a variety of nitrogen nucleophiles is accomplished using magnesium perchlorate (150 mol %) as the Lewis acid in acetonitrile at 80 °C in 73-97% yield. 252 After the pioneering work of Crotti in 1991 on the ringopening of epoxides with nucleophiles such as lithium enolates 253 and amines, 254 in recent years, the Azizi and Saidi group has improved and developed the applications of LiClO 4 as a promoter in this reaction with various nucleophiles such as amines (20 mol %, 80-97% yield), 255 thiols (12.5 mol %, 90-98%), 256 chlorides (10 mol %, 82-97%), 257 azides (33 mol %, 45-78%), 257 and cyanides (10 mol %, 84-97%) 258 under solvent-free conditions at room temperature. It should be noted that the reaction of cyclohexene oxide with TMSCN is carried out in the presence of other perchlorates (Mg(II), Ni(II), Fe(III), and LiClO 4 -SiO 2 ) under solvent-free conditions, but they show lower activity.…”

Section: Epoxidesmentioning

confidence: 99%

Perchloric Acid and Its Salts: Very Powerful Catalysts in Organic Chemistry

et al. 2010

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Preparation of Chiral 5,6-trans-Disubstituted Phenanthrolines from Phenanthroline-5,6-epoxide

Cited by 10 publications

References 7 publications

Auto-Assembling of Ditopic Macrocyclic Lanthanide Chelates with Transition-Metal Ions. Rigid Multimetallic High Relaxivity Contrast Agents for Magnetic Resonance Imaging

Auto-Assembling of Ditopic Macrocyclic Lanthanide Chelates with Transition-Metal Ions. Rigid Multimetallic High Relaxivity Contrast Agents for Magnetic Resonance Imaging

First isolation of disubstituted cis‐5,6‐dihydro‐1,10‐phenanthrolines. lipase‐mediated resolution of cis‐ and trans‐phenoxy alcohol isomers and assignment of absolute stereochemistry via cd and nmr spectroscopy

Perchloric Acid and Its Salts: Very Powerful Catalysts in Organic Chemistry

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