62617-39-4Relevant articles and documents
Hydrothermal synthesis of chiral inorganic-organic CoII complex: Structural, thermal and catalytic evaluation
Salah, Assila Maatar Ben,Herrera, Raquel P.,Na?li, Houcine
, p. 356 - 362 (2018/05/29)
By heating the cobalt chloride hexahydrate (CoCl2·6H2O) with the R form of the organic amine α-methylbenzylamine (C8H11N) under hydro(solvo)thermal conditions, we have successfully generated the corresponding non-centrosymmetric homochiral hybrid tris (α-methylbenzylammonium tetrachloridocobaltate chloride [R-(C8H12N)3][CoCl4]Cl abbreviated R(MBA)Co. We present the growth conditions together with a characterization of the single crystals by means of X-ray single-crystal diffraction, Fourier-transform infrared, TG/TDA thermal decomposition and catalytic properties. This inorganic–organic hybrid compound crystallizes in the chiral space group P21 and exhibits a supramolecular-layered organization wherein a double layer of (R)-methylbenzylammonium cations and the uncoordinated chloride anions are sandwiched between anionic layers, formed by isolated tetrachloridocobaltate tetrahedra. The crystal packing is governed by a three-dimensional network of N/C–H?Cl hydrogen bonds between the inorganic and organic moieties and C–H···π interactions between the aromatic rings of the organic moieties themselves. Thermal analysis discloses a phase transition at the temperature 130 °C. The Co complex was also employed as suitable catalyst activating the acetal formation reaction of aldehydes using MeOH as solvent and as the unique source of acetalization.
Crystallisation, thermal analysis and acetal protection activity of new layered Zn(II) hybrid polymorphs
Sa?d, Salem,Na?li, Houcine,Bataille, Thierry,Herrera, Raquel P.
, p. 5365 - 5374 (2016/07/21)
Two new polymorphic mononuclear complexes, with analogous structural formula (C6H9N2)2[Zn(H2O)6](SO4)2·2H2O, of zinc(ii) templated by 2-amino-6-methylpyridinium ligand have been discovered. These polymorphic hybrid crystals, which differ only in terms of their crystal structures, were prepared in one-step synthesis under ambient conditions and investigated for their thermal and catalytic properties. Single-crystal X-ray diffraction of the obtained materials revealed that polymorphs 1 and 2 crystallise in the triclinic system, space group P1. In an effort to further explore the form diversity of these compounds, the structural arrangements and intermolecular interactions such as hydrogen-bonding and π?π interactions are discussed from which supramolecular assembly was formed. Meanwhile, these new polymorphic forms can be described as the stacking of 3D layers where the interlayer distances are 13.23 and 12.59 ? for 1 and 2, respectively. The thermal behaviour of the precursors checked by TG-DTA analysis for both zinc sulfate polymorphs and variable temperature powder X-ray diffraction (VT-PXRD) show successive intermediate crystalline anhydrous phases upon dehydration in 1. The catalytic activity of both polymorphic structures has been tested in the acetalisation reaction of aldehydes as a benchmark process. Interestingly, both complexes showed excellent activity with almost total conversion in many examples and using MeOH as solvent and as the unique source of acetalisation.
Catalytic asymmetric phase-transfer reactions using tartrate-derived asymmetric two-center organocatalysts
Ohshima, Takashi,Shibuguchi, Tomoyuki,Fukuta, Yuhei,Shibasaki, Masakatsu
, p. 7743 - 7754 (2007/10/03)
A new highly versatile asymmetric two-center catalyst, tartrate-derived diammonium salt (TaDiAS), was designed and a catalyst library containing more than 70 new two-center catalysts was constructed. A variety of (S,S)- and (R,R)-TaDiAS were easily synthesized from diethyl L- and D-tartrate, respectively, using common and inexpensive reagents under operationally simple reaction conditions. TaDiAS was used in phase-transfer alkylations and Michael additions to afford various optically active α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst (acetal, Ar, and counter anion) for optimization. Recovery and reuse of the catalyst was also possible using simple procedures. The present asymmetric PTC was successfully applied to enantioselective syntheses of serine protease inhibitor aeruginosin 298-A and its analogues.
Efficient acetalisation of aldehydes catalyzed by titanium tetrachloride in a basic medium
Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
, p. 15679 - 15690 (2007/10/03)
The acetalisation of aliphatic and aromatic aldehydes is achieved in a basic medium by using catalytic amount of Ti(IV) chloride in MeOH in the presence of NH3 or Et3N. The present protocol shows many advantages over the well known base or acid catalysis: in fact, in contrast to base-promoted acetalisation, aldehydes with electron-rich carbonyl groups react easily, enolizable aldehydes do not undergo aldol condensation and, in contrast to acid-catalysis, migration of the double bond does not occur in the preparation of α,β-unsaturated acetals.
Stereoselective Alkylierung an C(α) von Serin, Gycerinsaeure, Thereonin und Weinsaeure ueber heterocyclische Enolate mit exocyclischer Doppelbindung
Seebach, Dieter,Aebi, Johannes D.,Gander-Coquoz, Marlyse,Naef, Reto
, p. 1194 - 1216 (2007/10/02)
The chiral, non-racemic title acids are converted to methyl dioxalene- (cf. 13), oxazoline- (4) and oxazolidine-carboxylates (cf. 9).Deprotonation by Li(i-Pr)2N at dry-ice temperature gives solutions of the litium enolates A-D with exocyclic enolate double bonds.These are stable enough with respect to β-elimination (Scheme 1) to be alkylated with or without cosolvents such as HMPA or DMPU.The products are formed in good to excellent yields and, with the exception of the tartrate derived acetonide (see Schemem 2), with diastereoselectivities above 90percent.While the tartrate- and threonine-derived enolates (A and B, resp.) are chiral due to the second stereogenic center of the precursors, the serine- and glyceric-acid-derived enolates are non-racemic due to a tert butyl-substituted (pivalaldehyde-derived) acetal center (C and D, resp.).The products of alkylation can be hydrolyzed to give α-branched tartaric acid (Scheme 2), allothreonine (Scheme 3), serine (Scheme 4), and glycerine-acid derivatives (Scheme 5) with quaternary stereogenic centers.The configurations of the products are determined by NOE-NMR measurements and by chemical correlation.These show taht the dioxolane-derived enolates A and D are alkylated preferentially from that face of the ring which is alredy substituted ('syn'-attack).The 'syn'-attack is postulated to arise from strong folding of the heterocyclic ring due to elelctronic repulsion between the enolate ?-system and non-bonding elelctron pairs on the heteroatoms (see Scheme 6).
Photochemistry of Alkyl Halides. 9. Geminal Dihalides
Kropp, Paul J.,Pienta, Norbert J.
, p. 2084 - 2090 (2007/10/02)
The photobehavior of the geminal dihalides (diiodomethyl)cyclohexane (7), (bromoiodomethyl)cyclohexane (11), (dibromomethyl)cyclohexane (17), (diiodomethyl)cyclopentane (22), 3,3-dimethyl(diiodomethyl)cyclobutane (27), and 8,8-diiodo-2,6-dimethyl-2-octene (31) has been studied and compared with that previously observed for diiodomethane.In all solvents the corresponding vinyl halides (iodomethylene)cyclohexane (13), (bromomethylene)cyclohexane (21), (iodomethylene)cyclopentane (23), 3,3-dimethyl(iodomethylene)cyclobutane (28), or cis- and trans-3,7-dimethyl-1-iodo-1,6-octadiene (33) were obtained, which are thought to arise from α-halo cationic intermediate formed via initial light-induced homolytic cleavage of the carbon-iodine bond followed by electron transfer within the resulting caged radical pair, as shown in Schemes II and III.In the case of diiodide 31 competing intramolecular trapping of the α-iodo cation afforded in addition the cyclized isopulegyl iodide (34).In polar solvents the vinyl iodides were accompanied by the nonhalogenated products methylenecyclohexane (15), 1-methylcyclopentene (25), cyclohexene (26), 4,4-dimethylcyclopentene (29), and cis- and trans-carane (35), which are thought also to arise from the α-halo cationic intermediate. 1.1-Diiodo-2,2-dimethylpropane (1b) afforded 2-methyl-2-butene (6b).Except for carane (35) from diiodide 31 there was no detectable formation of cyclopropanes.In methanol the nucleophilic substitution products (dimethoxymethyl)cyclohexane (14), (dimethoxymethyl)cyclopentane (24), and 1,1-dimethoxy-2,2-dimethylpropane (30) were obtained.It is concluded that geminal dihalides undergo predominant, if not exclusive, photoreaction via initial clea vage of a single carbon-halogen bond in analogy with monohalides and that carbene intermediates are not formed.A similiar conclusion has been reached previously for diiodomethane in the photocyclopropanation of alkenes.
