Stereospecific beta-lithiation of oxazolinyloxiranes: synthesis of alpha,beta-epoxy-gamma-butyrolactones

[reaction: see text]. Stereospecific beta-lithiation of beta-aryl-substituted oxazolinyloxiranes is described. The trapping reaction of such reactive intermediates with carbonyl compounds gave alpha,beta-epoxy-gamma-butyrolactones after deblocking of the oxazoline moiety. This methodology has been also extended to the synthesis of optically active alpha,beta-epoxy-gamma-butyrolactones.     

Reaction between N-acyl-2,3-dihydrobenzo-1,4-thiazine and N-acylphenothiazine with organometallic reagents

the title $\text{N}$-acyl-derivatives react with $\text{n}$-BuLi and Grignard reagents leading to products, which, formally, can be considered as derived from a Claisen-type condensation reaction.     

On the lithiation of oxazolinylaziridines

Lithiated N-sulfonyloxazolinylaziridines 6a and 7a, generated by deprotonation of the corresponding aziridines 6 and 7 with sec-BuLi/TMEDA at −98°C in THF, were found to be chemically and configurationally stable to be stereospecifically captured by electrophiles, while warming up to rt resulted in the formation of oxazolinylazirine 15. In contrast, lithiation of N-phenyloxazolinylaziridines 8 and 9 led to oxazolinylenamine 18. Tricyclic aziridines 10 and 11 resulted from an intramolecular addition of the aziridinyllithium 6a to the phenyl ring of the benzenesulfonyl group.     

Reactivity of 4-nitro- and 4-nitro-7-halogeno-2,1,3-benzothiadiazoles toward methoxide ion

4-Nitro-2,1,3-benzothiadiazole reacted with sodium methoxide (0.1-1 M) in methanol yielding 2,1,3-benzothiadiazole-4, 7-dione monoxime (syn+anti). Methoxy-dehalogenation of 4-nitro-7-halogeno-derivatives yielded 4-nitro-7-methoxy-2,1,3-benzothadiazole under similar conditions. In both eases transitions attributable to the formation of Meisenheimer complexes were detected.     

Directed ortho lithiation of N-alkylphenylaziridines

The ortho lithiation-trapping sequence of phenylaziridines is described. This methodology, which counts on the ability of the aziridino group to act as a directed metalation group (DMG), provides an easy access to functionalized arylaziridines as well as to phthalans and phthalides. The importance of the aziridine N-substituent in this DoM reaction is stressed as well. [reaction: see text]     

Alpha- vs ortho-lithiation of N-alkylarylaziridines: probing the role of the nitrogen inversion process

The lithiation reaction of monophenyl- and diphenylaziridines has been investigated in detail in an effort to understand why the former undergo exclusively or mainly ortho-lithiation while the latter are lithiated exclusively at the alpha-position. Evidence is reported that ruled out the possibility that the alpha-lithiation, observed for the diphenylaziridines, is the result of an ortho- to alpha-translocation phenomenon, thus substantiating a direct alpha-deprotonation process. The role of the aziridine nitrogen lone-pair has been considered: dynamics at the aziridine nitrogen as well as complex-induced proximity effects seem to be responsible for the observed regioselectivity in both monophenyl and diphenylaziridines. It turns out that, by tuning the reaction conditions for the lithiation of trans-1-alkyl-2-methyl-3-phenylaziridines, it is possible to generate with high regioselectivity alpha- and/or ortho-lithiated aziridines, which can be stereoselectively functionalized by electrophilic trapping. A regioselective ortho-functionalization of diphenylaziridines is made possible by halogen- or tin-lithium exchange and by deprotonation of bis-deuterated aziridines.     

Molecular design of star-shaped benzotrithiophene materials for organic electronics

Progresses in the design and application of conjugated small molecules, oligomers and polymers have empowered rapid development of organic electronic technology as an alternative to conventional devices. Among the numerous organic electronic materials, benzotrithiophene (BTT)-based oligomers and polymers have recently come in the limelight demonstrating great potential in organic electronics as high performance photovoltaic devices, field-effect transistors, electrochromic materials, high-area capacitors and charge carrier discotic liquid crystals. In this digest, we propose an overview of the organic electronic materials based on BTT isomers, highlighting the structure-performance relationship. The results obtained so far clearly indicate that the BTT isomers are among the most promising building blocks for the development π-extended materials for optoelectronic applications in the near future.     

Direct synthesis of aromatic polyamides

The synthesis of aromatic polyamides, namely poly(p-phenylenetere-phthalamide) and poly(p-benzamide), via phosphorylation reaction has been thoroughly investigated. The effect of reaction temperature, concentration of monomers and reactants, type and concentration of salts, amount of the activator and its stepwise addition have been considered and the optimum reaction conditions found. The resultant synthesis of the above polymers, also in connection with the high purification techniques of all components of the reaction mixture, allowed to reach the highest molecular weights obtained so far by this synthetic way.     

Hyperbranched aramids by direct polyamidation of two reactant systems: Synthesis and properties

Some A₂ + B₃ and A₃ + B₃ reagent pairs have been used for the direct polyamidation reaction leading, besides the network formation, to hyperbranched aramid structures. Depending on the chosen experimental conditions, variable amounts of a sol fraction having close similarities with the hyperbranched aramid structures derived from the polyamidation of AB₂ monomers, have indeed been obtained. Solubility of the sol fraction in various organic solvents, as well as its thermal properties and its capability of enzyme fixation, have been determined for the various systems under investigation. Future developments are envisaged.     

Synthesis of hyperbranched aromatic polyamides by direct polycondensation

Some hyperbranched aromatic polyamides have been synthesized by direct polycondensation using the modified Higashi's method. Structures of the above polymers have been realized taking in proper account the analogies with amide group sequences of poly(p-phenyleneterephthalamide) (PPDT) and poly(p-benzamide) (PBA). Therefore, AB₂- type monomers as well as suitable combinations of different bi- and trifunctional reactants (AA + B₃) (e.g., p-phenylenediamine + trimesic acid or other trifunctional acids) have been considered. For the latter systems, network formation has been minimized. In the present paper, our results on their direct polyamidation together with some preliminary characterization data on the resultant hyperbranched aramids are given.