Phase chromonics

Luckhurst potential, dimers 816 luminance, guest-host effect 272 lutetium, phthalocyanine ligands 924 lyotropic blue phases, chromonics 998 lyotropic systems... 

Method A The 2-hydroxyacetophenone (3 mmol) and acyl chloride (3.6 mmol) in PhH (20 ml) are stirred at 80°C with aqueous K,CO, (I0%, 20 ml) and TBA-HS04 (0.5 g, 1.5 mmol) for 2-3 h until the ester is completely formed. The PhH phase is separated, washed with H.O (3 x 20 ml) and dried by azeotropic distillation. Ring closure is effected by the addition of TosOH (1.55 g, 9 mmol) in PhH (20 ml) and azeotropic distillation. The organic solution is washed with aqueous NaHCO, (10%, 50 ml) and evaporated to yield the chromone. 

Method B The acyl chloride (12 mmol) in CH2C12 (10 ml) is added dropwise over 15 min to the 2-hydroxyacetophenone (10 mmol), TBA-HS04 (0.1 g, 0.3 mmol) and aqueous K,CO, (20%, 30 ml) at room temperature. The mixture is stirred for ca. 7 h and the organic phase is then separated, washed well with H20 and brine, dried (MgS04), and evaporated to yield the chromone (70-95%). 

Another problem for the synthetic use of PFR is that the ortho-rearranged products may act as internal light filters, stopping the reaction. In synthetic routes leading to chromanones, chromones, and related compounds, this is of vital importance because the overall yield is limited by the photochemical step. Improved yields can be obtained if the a, 3-unsamrated orr/io-hydroxyphenones resulting from PFR are removed and cyclized to chromanones. This can be acomplished in one pot by irradiation in a two-phase system benzene/10% aqueous NaOH, whereby chromanones are directly obtained from phenyl crotonates in 80-90% yields [210]. 

Examples of thermochemical considerations of cupric enolates include the study of the binding of Cu + with kojic acid (16), a cyclic a-ketoenol. Comparison was made between the divalent cations of U02 +, Cu +, Zn +, Ni +, Co +, Cd +, Ca + where these metals are listed in decreasing order of binding constants over 6 powers of 10. In this case carbon-bonded metal seems most unreasonable because it would ruin the chelation as well as any aromaticity in the pyrone ring. It is admittedly an assumption that pyrones are aromatic. There are no one-ring pyrones for which there are enthalpy of formation data for gas phase species, as opposed to the benzoannelated compounds coumarin (I7)i07a, I07b chromone (is) " " "and xanthone (19) . Plausible, but unstable, Cu(II) enolates eliminate copper and form the 1,4-dicarbonyl compounds as shown in equation 8. 

LCs typically have an aromatic organic core with ionic groups lining the periphery, giving them a disk- or plank-like shape (e.g., ionic organic dye molecules). They are technically classified as LLCs because they can self-assemble into ordered phases in the presence of water. However, unlike traditional amphiphiles, lyotropic chromonic LCs are rigid rather than flexible, and their hydrophobic components are based on aromatic units rather than aliphatic chains. Unlike traditional amphiphilic LCs, they self-organize in so-... 

Fig.4 Structure of a typical lyotropic chromonic LC, and schematic representations of two lyotropic chromonic LC phases. Reproduced with permission from [10]. 2004 by Elsevier...

In addition to those formed by surfactant amphiphiles, two other types of lyotropic mesophases are generally recognized, neither of which exhibits a cmc. The first of these are lyotropic phases of rigid-rod polymers that can form mesophases in both aqueous and non-aqueous solvents " these mesophases are of the nematic or hexagonal type. Examples include polymeric metal acetylide complexes and DNA." The other type is usually formed from flat and largely aromatic molecules which stack to give lyotropic columnar phases, also referred to as chromonic phases." " This latter class is formed from systems with ionic or strongly hydrophilic peripheral functions, and forms mesophases... 

A few pyrazolo-[3,4-e]-2H-pyrans were made 6 m the heterocyclization of l-phenylpyrazolidine-3,5-dione with active nitriles, under phase-transfer catalysis conditions (14JHC860). The natural chromone-fused 2H-pyran macakurzin C was obtained from phlorc ucinol in a multistep synthetic approach, a Claisen rearrangement-cyclization of propai loxychromone derivative being the key transformation to build the pyran core (14SL2794). 

Reversed-phase HPLC is the method recommended for the screening of plant materiaL in which chromone alkaloids can be present. Mostly C-18 columns were applied with aqueous mobile phases containing high concentrations of buffer at pH 4.5-6.5, modified with methanol or acetonitrile. Polyhydroxy alkaloids of the pyrrohdine, piperidine, pyrro-lizidine, indolizidine, and tropane classes, because of their lack of a suitable chromophore, have rarely been analyzed... 

The tendency for the molecnles of chromonic phases to aggregate into colnmns is present even in dilute solution where colnmn formation occnrs before a phase is formed. Althongh there may be a threshold concentration before aggregation begins to occur, there is no optimum column length and hence no critical concentration, with a further distinction being the absence of a Krafft temperature. Since the process of mesophase formation does not depend on the presence of flexible alkyl chains, there is no threshold temperature below which mesophases cannot form because the vital flexibility of the molecules has been frozen out. 

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