Tuvia Sheradsky

Introduction of the aminooxy group on to nitroaromatic and heterocyclic rings : Synthesis and properties of O-(nitroaryl)hydroxylamines

Abstract The reaction of halonitrobenzenes with t-butyl N-hydroxycarbamate ( 2 ), gave t-butyl N(nitroaryloxy)carbamates ( 3 ), which yielded on acidolysis with trifluoroacetic acid, O-(nitroaryl)hydroxylamines ( 4 ). Compounds 4 were utilized for the amination of anionic nitrogens and of carbanions. Attempts to apply the method to the synthesis of hydroxylamines substituted on the oxygen by heterocyclic rings (pyridine, pyrimidine, pyrazine, triazine, purine and benzothiazole) yielded only the corresponding hydroxy compounds. However, the formation of a N,O-dipyridylhydroxylamine derivative ( 22b ) indicates that O(5-nitro-2-pyridyl)hydroxylamine ( 17 ) existed as a highly reactive intermediate.

Synthesis of polymers with isolated thiophene-based chromophores

The polymers presented in this paper are designed for the intended use in light-emitting diodes. The synthesis of a new series of macromolecules containing isolated oligothiophene, oligothienylene vinylene, or bithiazole conjugated units bridged by aliphatic units is presented along with optical characterization by UV−vis absorption and fluorescence spectra in solution. These polymers gave very similar optical traits to their corresponding subunits while possessing the physical characteristics of a macromolecule.

INTRAMOLECULAR NUCLEOPHILIC SUBSTITUTION ON NITROGEN. A NEW HETEROCYCLIC SYNTHESIS

Abstract A series of 5-(diphenylphosphinyloxyamino)valeric acid esters has been prepared. Their treatment with appropriate bases led to cyclization to proline derivatives. The reaction constitutes the first reported case of intramolecular nucleophilic substitution on nitrogen.

Synthesis of polymers with isolated thiophene–arylidene–thiophene chromophores for enhanced and specific electron/hole transport

The synthesis of nine new polymers intended for future use in light-emitting diodes is described. The polymers consist of alternating units of thiophene–arylidene–thiophene chromophores and saturated silicon-containing spacers. The arylidene moieties include benzene-1,4-, 2,5-dimethoxybenzene-1,4-, naphthalene-1,4-, anthracene-9,10-, pyridine-2,5-, pyridine-2,6-, N-methylcarbazole-3,6-, 1,3,4-oxadiazole-2,5-, and 4,4′-dimethyl-2,2′-bithiazole-5,5′-. The syntheses involved dibromination of the central arene followed by Suzuki or Kumada cross-coupling reactions with two thiophene units. Subsequent dilithiation and reaction with dihalosilylalkanes provided the polymers. Their optical properties, including ultraviolet–visible absorption and emission in solution, were comparable to those of the parent monomer units, and they possessed the physical characteristics of macromolecules.

Adjustable electroluminescence: blue-green to red organic light-emitting diodes based on novel poly-non-conjugated oligomers

Two new polymers, poly-9,10(1,3-bis(4-ethynylphenoxy)propane)anthracene and poly-1,2(tetra-2,5-thienylene-1,2-vinylene)dimethylsilyslethane, based on conjugated chromophores that are interconnected via non-conjugated spacers, were prepared and characterized in terms of their photo- and electroluminescence (PL and EL, respectively) properties in pure films and in solid solutions. The application of solid solutions of the two polymers in PVK:PBD (polyvinyl carbazole:2-(4-biphenyl)-5-(4-tert-buthyl phenyl)-1,3,4-oxadiazole) matrices as active layers in adjustable blue-green to red OLED is presented.

Polymers containing backbone fluorescein, phenolphthalein and benzaurin. Synthesis and optical properties

In order to utilize the prominent fluorescence ability of fluorescein in light emitting devices, we have synthesized a series of polymers that contain fluorescein in their backbones. The key step of the synthesis, in which the fluorescein unit and the polymer are created simultaneously, is the reaction of bis(2,4-dihydroxyphenyl)alkanes with phthalic anhydride. This new methodology was also used for the synthesis of polymers containing phenolphthalein and benzaurin. All the new polymers completely maintained the optical and chemical characteristics of the parent pigment.

Photochemical transformations. Part 36. Synthesis and photolytic ring contraction of mesoionic 2-alkylthiothiazol-4-ones; a new route to β-lactams

A number of mesoionic 2-alkylthiothiazol-4-ones (6) were prepared by alkylation of rhodanines or by the reaction of α-bromomalonates with dithiocarbamates. The photolysis of these mesoionic compounds proceeds via a highly strained, bicyclic, ling contraction product which rearranges to a thiazolin-2-one (14), loses sulphur, affording a β-aminoacrylate (11), or is trapped by methanol giving methoxy-β-lactams (12) and (13).

Intramolecular oxidative diels-alder reaction of n-sorbyl-l-proline acylhydrazides

Abstract Oxidation of the title compounds to the corresponding azo derivatives resulted in an intramolecular Diels-Alder reaction with complete asymmetric induction. The two newly formed chiral centers have R configuration.

Reaction of mesoionic thiazol-4-ones with azodicarbonyl dipolarophiles. Cleavage modes of the bi- and tri-cyclic adducts

The thiazolium-4-olates (1a–e) were treated with dimethyl and diethyl azodicarboxylate and gave, through 1,3-dipolar cycloaddition, the 3,6-sulphur bridged hexahydro-1,2,4-triazin-5-ones (2). When heated in benzene these rearranged to the blue thioxohydrazides (3), whilst when heated in methanol or ethanol they reacted with the solvent to give 2-alkoxy-5-hydrazinothiazol-4-ones (4). Reaction of the mesoionic compounds (1) with 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) gave the cycloadducts (11) which reacted very readily with water or alcohols to give the thiazol-4-ones (5), analogous to (4). The structures and stereochemistry of (2), (3), and (5) were established by X-ray analyses. The mechanisms of the ring openings of (2) to (3) and (4), and of (11) to (5) are discussed.

Reaction of carbanions with N-tosyloxyphthalimide. Formation of 3,3-disubstituted quinoline-2,4-diones

The reaction of a series of carbanions, including both aromatic anions and enolate anions, with N-tosyloxyphthalimide gave 3,3-disubstituted quinoline-2,4-diones. A multi-step mechanism which involves attack of the carbanion on a carbonyl group, ring opening, Lossen-like rearrangement, intermolecular proton transfer, and ring closure is suggested.