Maria Gisbert

A direct synthetic approach to novel quadrupolar [14] azolophanes

Abstract A convergent ‘3+1’ synthesis allowed a simple entrance to the first examples of [1 4 ] meta azolophanes 1 and [1 4 ]( meta-ortho ) 2 azolophanes 2 built up from heterocyclic betaine subunits, illustrating a prototype of phanes constructed by both highly π-excessive and highly π-deficient heteroaromatic moieties linked in a 1,3-alternating fashion.

Quadrupolar [14](meta—ortho)2azolophanes. Intramolecular C—H…N and to Water C—H…O hydrogen bonding revealed by X-ray diffraction

Abstract The first X-ray crystallographic diffraction of an example of the title heterophanes built up from heterocyclic betaine subunits is reported and its quadrupolar character is confirmed. The crystal packing of 2·4H2O is mainly governed by hydrogen-bonding networks, strong intermolecular interactions with water together with weak interactions, either intramolecular or with water.

Design of unusual captodative methylene substrates: 1-Alkyl-4(3)-(azolylmethyl)pyridinium salts 1

Abstract The unprecedented spontaneous oxidation of a carbon atom linked to captor (acceptor) and donor non-classical functional groups of several examples of 1-alkyl-4(3)-(1H-azolylmethyl) pyridinium salts 1 and 2 exemplifies a concomitant application of the arenoanalogy principle and the captodative effect in organic synthesis. A remarkably driving force by the nature of non-classical acceptor and donor heteroaromatic rings is observed upon the chemical behavior of the title compounds 1 and 2, modulating the susceptibility with which the methylene spacers oxidize to their oxomethyl counterparts 5 and 6. Access to dipolar 1-alkyl-3-pyridiniomethyl-3(5)-1,2,4-triazolate inner salts 4 was achieved.

UNCONVENTIONAL ACCEPTOR AND DONOR FUNCTIONAL GROUPS LINKED BY A CAPTODATIVE SPACER

Abstract The chemical stability to oxidation of a set of compounds built up from acceptor and donor submits linked by a methylene or a hydroxymethylene group was studied. Whereas 1-butyl-3-[1,2,4-triazol-5(3)-ylmethyl]pyridinium salts 2d,e showed high stability to oxidation, 1-butyl-4-[imidazol-4(5)-ylhidroxymethyl]pyridinium salt 14f was oxidised spontaneously to the corresponding carbonyl compound, indicating the capability of the oxidation phenomenon to be controlled by the nature of the building blocks.

Application of the Kauffmann Areno-Analogy Principle − Stability towards Oxidation of the Methylene Spacers in Quadrupolar [14]Heterophane Frameworks Incorporating 4- or 3-Pyridiniomethyl-1,2,4-triazolate Betaine Units

Incorporation of 3,5-bis-3(4)-pyridiniomethyl-1,2,4-triazolate units into the structures of novel bis-betaines in [14](meta-para)2heterophane systems has shown that the structural features conferred by the heterophane framework result in macrocycles that, in contrast to their building blocks, are stable towards oxidation. The stability of [14]metaheterophanes is consistent with their betaine subunits.

Novel captodative methylene compounds. Spontaneous oxidation of 1-alkyl-4(3)-(azolylmethyl)pyridinium salts

For several examples of the title compounds 4–7 and 12 the nature of the non-classical acceptor and donor heteroaromatic moieties modulates the susceptability of the methylene spacer towards oxidation.