Juan Luis Lopez

AZA-WITTIG REACTIONS OF IMINOPHOSPHORANES DERIVED FROM FERROCENYLAZIDO KETONES : PREPARATION AND ELECTROCHEMICAL STUDY OF NOVEL FERROCENYL-SUBSTITUTED AZAHETEROCYCLES

Abstract α-Azidoacetylferrocene and 3-(o-azidophenyl)-1-ferrocenylpropenone have been prepared from acetylferrocene and they have proven to be useful building blocks for the synthesis of azaheterocycles. Thus, the three-component reaction of α-azidoacetylferrocene, isocyanates or acid chlorides and triphenylphosphine allows the direct formation of ferrocene-substituted oxazoles. Aza-Wittig reaction of the iminophosphorane derived from 3-(o-azidophenyl)-1-ferrocenylpropenone with isocyanates provides access to the corresponding carbodiimides which are cyclised either by the action of TBAF or amines to give ferrocenyl-substituted dihydroquinazoline derivatives. The bis(ferrocenyl)oxazole 13 showed in the cyclic voltammogram (†E 1 2 = 150 mV) moderate electronic coupling between the two ferrocenes through the oxazole ring.

Preparation and heterocyclization reactions of ferrocenylazido ketones. Useful building blocks for the synthesis of ferrocenyl-substituted azaheterocycles

Abstract Several kinds of ferrocenylaryl ketones bearing an azido functionality at the ortho -position of the aryl ring have been prepared and they have proven to be useful building blocks for the synthesis of azaheterocycles. Thus, thermally induced azide decomposition of these compounds allows the formation of ferrocene-substituted 2,1-benzisoxazoles and indoles. Moreover, the Staudinger reaction with triphenylphosphine followed by aza-Wittig reaction of the resulting iminophosphorane with isocyanates provides access to ferrocene-substituted quinolines and quinazolinones.

Preparation of a novel class of macrocycle and cryptand containing the 1,1′-disubstituted ferrocene unit

Condensation of 1,1′-diacetylferrocene with o-azidobenzaldehyde under appropriate conditions leads either to the [5]-ferrocenophane 2 or the bis(azide) 3, as the only reaction products. Compound 2 undergoes an intramolecular aza-Wittig reaction to give the new type of cryptand 4. Bis(azide) 3 is converted into the macrocycle 5 by a Staudinger reaction with bis(diphenylphosphino)ethane; alternatively, thermally-induced azide decomposition provides the 1,1′-bis(indolyl)ferrocene derivative 6.

Intramolecular heteroconjugate addition of heterocumulenes to α,β-unsaturated carbonyl compounds promoted by the CS2/TBAF system

Abstract We describe a new method for the preparation of dihydroquinazoline-2-thione and 4H-3,1-benzothiazine-2-thione derivatives by intramolecular heteroconjugate addition of carbodiimides or isothiocyanates bearing one o-substituted α,β-unsaturated carbonyl fragment promoted by the CS2/TBAF system.

Modulation of the metal recognition properties of a new type of azaferrocenophane-based chemosensors: co-ordination chemistry towards Mg2+, Ca2+, Zn2+ and Ni2+

The structure-redox chemistry relationship of a new type of azaferrocenophane-based chemosensors, 3 and 4, in the presence of protons and several kinds of metal ions, has been studied. Electrochemical studies, carried out in CH2Cl2, in the presence of increasing amounts of Mg2+, Ca2+, Zn2+ and Ni2+ showed that the wave corresponding to the Fc/Fc+ couple of the uncomplexed ligands is gradually replaced by a new reversible wave at more positive potentials corresponding to the Fc/Fc+ couple of the complexed ligands. The maximum shift of the ferrocene oxidation wave was found for 4b in the presence of Mg2+, whereas for 3f a selective sensing response for Mg2+ in the presence of hydrated Ca2+ cations was observed, with a concomitant highly visual output response consisting of a deep purple colour.

A new insight into the problem of stabilisation of α-carbocationic centres in the ferrocene series

Two different modes of stabilisation of the α-carbocationic centre in the diferrocenylcarbenium ion 4, available from the [5]ferrocenophane 1 by sequential treatment with ferrocenyllithium and tetrafluoroboric acid, are clearly demonstrated by a combination of 1H NMR and 57Fe Mossbauer spectroscopies.

New strained ferrocenophane-based receptors for the selective electrochemical recognition of Mg2+ in the presence of Ca2+ cations

Abstract Ferrocenophane derivatives 3 act as electrochemical sensors of Mg2+ ions: a new redox peak appears in the CVs anodically shifted compared to the E1/2 of the free receptors by 268–382 mV. Receptors 3a , 3c and 3d are selective for Mg2+, whilst 3b is also responsive to Ca2+ ion (302 mV shift). Receptor 3c also gave a highly visual output response in the presence of Mg2+ consisting of a deep purple colour.

Synthesis and electrochemical properties of a new range of strained 2-aza-[3]ferrocenophanes

Abstract The previously unreported 2-aza-[3]ferrocenophanes 3 and 4 , prepared from a preformed [5]ferrocenophane, act as electrochemical sensors either of Mg 2+ , Zn 2+ and Ni 2+ cations (free ligand): a new redox peak appears in the CV shifted 310–360 mV or hydrogensulfate anion (protonated ligand) via a significant cathodic perturbation.