Stephen T. Astley

Structure and Luminescent Properties of the 4-Arylidene-2-Aryl-5-Oxazolones(Azlactones)In Solution and Crystalline State

Abstract Experimental and theoretical evaluations have proven that very low fluorescence quantum yields of azlactones in solution are not caused by an efficient inter system crossing from S1*(ππ) to T*(nπ) states, but rather from solvation and steric effects, that result in non-planarity of the molecular system. High fluorescence quantum yields in the solid state are attributed to the planarity of the azlactone molecule upon packing into the crystal lattice. Supporting evidence was found upon observation of the excited state proton transfer (ESIPT) bands of fluorescence emissions of o-hydroxyarylidene derivatives. The photoinstability of azlactones in liquid states are attributed to photochemical E-Z isomerization and cleavage of the hetero ring α to the carbonyl group.

A beneficial effect of ortho-substituents in the arylation of (benzene)tricarbonylmanganese(1+) hexafluorophosphate(1−)

Abstract ortho -Substituted aryllithium and aryl Grignard reagents react with (benzene)manganesetricarbonyl cation ( 1 ) to give good yields of the expected ring adducts. The presence of the ortho substituent(s) appears to be necessary for the satisfactory outcome of the reaction with aryllithiums. This reactivity opens up the possibility of preparing novel heterocyclic structures via the initial reaction of 1 with functionalised metallated arenes.

Synthesis of novel Schiff base ligands from gluco- and galactochloraloses for the Cu(II) catalyzed asymmetric Henry reaction.

A series of chiral Schiff base ligands has been prepared using aminochloralose derivatives of glucose and galactose. These ligands were used as catalysts in the asymmetric Henry reaction in the presence of Cu(II) ions giving yields of up to 95%. An interesting solvent dependency on enantiomeric control was observed with the best enantiomeric excesses (up to 91%) being obtained in the presence of water.

trans-Diaqua­{5,5′-[(E,E)-pyridine-2,6-diylbis(methyl­idynenitrilo)]bis­[pyrimi­dine-2,4(1H,3H)-dione]}zinc(II) nitrate hexa­fluorophosphate trihydrate

The title compound, [Zn(C(15)H(11)N(7)O(4))(H(2)O)(2)](NO(3))(PF(6)).3H(2)O, contains a mononuclear zinc(II) complex. The Zn(2+) centre is seven-coordinated in a slightly distorted pentagonal-bipyramidal geometry, with the two water O atoms located in the apical positions, and the pyridine N atom, the two imine N atoms and two carbonyl O atoms of the uracil groups located in the equatorial plane. The charge is balanced by PF(6)(-) and NO(3)(-) anions.

STEREOCONTROLLED ORGANOMANGANESE SYNTHESIS OF CIS-4A, 10B-DIHYDROPHENANTHRIDINE DERIVATIVES

Abstract Cis-4a,10b-dihydrophenanthridine derivatives have been prepared in high yield via nucleophilic addition of a functionalised metalated arene to (benzene)tricarbonylmanganese(1+) hexafluorophosphate(1−) followed by reactivation, and intramolecular nucleophile addition.

Preparation of o-bromobenzophenone derivatives from lithium diarylcuprate(I) reagents

The reaction of lithium diarylcuprate(I) reagents with o-bromobenzoyl chloride has been investigated. In general, the reaction proceeds well to give synthetically useful o-bromobenzophenone derivatives as the major product. It is suggested that a minor substituent effect, whereby diarylcuprate reagents containing an ortho or meta substituent react more favourably, may be attributed to small changes in the structure of the organometallic reagent. Copyright

Catalyst functional group cooperativity in the amino acid-catalysed nitroaldol condensation reaction

Several amino acids and their derivatives have been evaluated as organic catalysts for the nitroaldol reaction. It was found that when an unprotected amino group and an unprotected carboxylate group were present in the organocatalyst, both the nitroaldol reaction and subsequent elimination could occur to afford nitroalkenes from aromatic aldehydes and nitromethane. The best results were obtained by use of γ-amino acids derived from l-glutamine. It is suggested that the amino group is important for intermediate Schiff base formation and that the free carboxylate group facilitates the elimination step.

Synthesis of Stable Acyclic Aminals Derived from L-(+)-Aspartic Acid and Their Application in Asymmetric Henry Reactions

A series of stable acyclic aminals derived from L-(+)-aspartic acid were synthesized in excellent yields (up to 96%) and characterized by spectroscopic methods. They were applied as enantioselective catalysts in Henry reactions of nitromethane with various aldehydes in the presence of Cu(II) ions, affording the corresponding adducts in high yields (up to 90%) and enantioselectivities (up to 92% ee). Graphical Abstract Synthesis of Stable Acyclic Aminals Derived from L-(+)-Aspartic Acid and Their Application in Asymmetric Henry Reactions

HIGHLY CHEMOSELECTIVE THIOCARBONYL OXIDATION UPON REACTION OF 4-METHYL-3-PHENYL-2-THIAZOLIDINETHIONE WITH SINGLET OXYGEN

Abstract 4-Methyl-3-phenyl-2-thiazolidinethione was reacted with both photochemically and chemically generated singlet oxygen. Despite reaction conditions which were selected to favor oxidation of the sulfide group, both reactions afforded a single product arising solely from thiocarbonyl oxidation.