S.V. Luis

Non concerted pathways in the generation of dehydroarenes by thermal decomposition of diaryliodonium carboxylates.

Abstract 1,3-Dehydrobenzene, 1,4-dehydrobenzene and 2,3-dehydronaphthalene are generated in the thermal decomposition of appropriate diaryliodonium carboxylates as demonstrated by the use of the three phase test. Intermediate species C6H4CO2 for m- and p-benzyne and C10H6CO2 for 2,3-naphthalyne have been unambiguously trapped in the same way, showing how non-concerted processes are the main pathway for generation of arynic intermediates from those iodonium salts.

Arynic species; effect of substituents on the reactivity of monosubstituted dehydrobenzenes

Abstract Evidence is presented demonstrating the existence of free dehydrobenzenes in the thermal decomposition of diaryliodonium-2-carboxylates, and that o-benzyne itself and its 4-methyl-, 4-chloro-,4-bromo- and 4-nitro-derivatives are generated from insoluble polymer-bound precursors and trapped by a second solid phase in Diels-Alder reactions. Lifetimes for these elusive species are determined.

Chemosensors displaying pH controlled multistage fluorescence emission

A large number of systems displaying pH controlled multistages of fluorescence emission intensity, have not been recognized from this point of view. In this work we present two paradigmatic cases: (i) polyamine receptors linked to a fluorophore unit, in which the signal is modulated by an intra-molecular pH dependent electron transfer process, (ii) phenols presenting adiabatic excited state proton transfer. In the first example the chemosensors are constituted by a receptor unit containing a polyaza moiety suitable for binding protons (but also metal ions or anions). The receptor is linked to a benzene or naphthalene unit that acts as a fluorophore. The fluorescence signal is dependent on the protonation state of the receptor. In the second example, addition of buffers are used to tune the intensity of the fluorescence emission.

The fischer indole synthesis of 8-methyl-5-substituted-1-oxo-β-carbolines: A remarkable high yield of a [1,2]-methyl migration.

Abstract A very unusual high yield of rearranged products (via methyl migration) has been obtained in the Fischer indole cyclization of the 3-(2,5-dimethyl phenylhydrazone) of 2,3-piperidine dione (6b). When a less activated aromatic ring is present in the phenylhydrazone 6, such a behaviour is not observed and cyclization occurs essentially without rearrangement.

Synthetic methods for the preparation of polystyrene resins containing chiral polyamine chains

Abstract The preparation of functionalized polystyrene-divinylbenzene resins containing functional groups derived from polyamine aliphatic chains has been studied. Best results are always obtained by direct alkylation of the polyamine with Merrifields polymers, but double alkylation at both end of the polyamine is observed. The procedure is useful for the preparation of polymer containing different chiral and non-chiral polyamine functionalities.

Arynic species II: Tosyl and triazene as leaving group in the generation of arynes from polymer-bound reagents

Abstract o-Benzyne and its 4-methyl, 4-chloro and 4-bromo-derivatives were generated in the thermal decomposition of two new kinds of polymer-bound precursors: 1(2-carboxyaryl)triazenes and 2-carboxyaryl-sulphonates. New kinds of trapping polymers for these elusive species are also presented.

Coamplexation of mercury(II) compounds by crown ethers in organic media

Complexes between crown ethers having ring sizes of 15–24 atoms and 5 to 8 oxygens with HgX2 species (X = Cl, I, CN, SCN) have been prepared and studied. Interactions of the substituents X bound to mercury with groups or fragments in the crown compound are essential in determining the characteristics and stability of the complexes formed. Complexes with crowns of 18C6 ring sizes are the most favourable except for HgX2 compounds for which the size of X is larger than the macrocycle ring, as is the case for X = CF3.

Generation of an unsaturated β-lactam intermediate from a polymeric precursor☆

Abstract A polymeric phase able to generate 1-azetin-4-one was prepared. The free existence of the reactive intermediate was demonstrated by trapping it with a nucleophilic polymeric agent. The mechanism of this reaction was established.

Evidence for the formation of 1,3- and 1,4-dehydrobenzenes in the thermal decomposition of diaryliodonium-carboxylates

Abstract Abstract: Generation of m- and p-benzynes in decomposition of diaryliodonium- 3- and 4-carboxylates is demonstrated by three-phase method.

Generation of monosubstituted o-benzynes from polymeric reagents via heterolytic fragmentations

Abstract Generation of four 4-substituted o-benzynes by heterolytic — fragmentation reactions is demonstrated.