Evaluating the Potential of Q-Band ESR Spectroscopy for Dose Reconstruction of Fossil Tooth Enamel.

The potential of Q-band Electron Spin Resonance (ESR) for quantitative measurements has been scarcely evaluated in the literature and its application for dose reconstruction of fossil tooth enamel with dating purposes remains still quite unknown. Hence, we have performed a comparative study based on several Early to Middle Pleistocene fossil tooth samples using both X- and Q-band spectroscopies. Our results show that Q-band offers a significant improvement in terms of sensitivity and signal resolution: it allows not only to work with reduced amounts of valuable samples (< 4 mg), but also to identify different components of the main composite ESR signal. However, inherent precision of the ESR intensity measurements at Q-band is clearly lower than that achieved at X-band, highlighting the necessity to carry out repeated measurements. All dose values derived from X- and Q-band are nevertheless systematically consistent at either 1 or 2 sigma. In summary, our results indicate that Q-band could now be considered as a reliable tool for ESR dosimetry/dating of fossil teeth although further work is required to improve the repeatability of the measurements.

Combined directed ortho-zincation and palladium-catalyzed strategies: Synthesis of 4,n-dimethoxy-substituted benzo[b]furans.

A new route to regioselectively dialkoxy-functionalized benzo[b]furan derivatives has been developed from 3-halo-2-iodoanisoles bearing an additional methoxy group, which have been accessed through an ortho-zincation/iodination reaction. Two palladium-catalyzed processes, namely a Sonogashira coupling followed by a tandem hydroxylation/cyclization sequence, give rise to new and interesting dimethoxy-substituted benzo[b]furans.

A practical, one-pot synthesis of highly substituted thiophenes and benzo[b]thiophenes from bromoenynes and o-alkynylbromobenzenes.

An efficient synthesis of thiophenes and benzo[b]thiophenes has been developed from easily available bromoenynes and o-alkynylbromobenzene derivatives. This novel one-pot procedure involves a Pd-catalyzed C-S bond formation using a hydrogen sulfide surrogate followed by a heterocyclization reaction. Moreover, in situ functionalization with selected electrophiles further expands the potential of this methodology to the preparation of the corresponding highly substituted sulfur heterocycles.

Approaches to the synthesis of 2,3-dihaloanilines. Useful precursors of 4-functionalized-1H-indoles.

2,3-Dihaloanilines have been proved as useful starting materials for synthesizing 4-halo-1H-indoles. Subsequent or in situ functionalization of the prepared haloindoles allows the access to a wide variety of 2,4- or 2,3,4-regioselectively functionalized indoles in good overall yields. As no efficient synthetic routes to 2,3-dihaloanilines have been described in the literature, different approaches to the preparation of these 1,2,3-functionalized aromatic precursors are now presented. The most general one involves a Smiles rearrangement from the corresponding 2,3-dihalophenols and allows the preparation of 2,3-dihaloanilides in a straightforward and synthetically useful manner.

Synthesis of regioselectively functionalized benzo[b]thiophenes by combined ortho-lithiation-halocyclization strategies.

An efficient synthesis of 3-halo-7-oxygen-functionalized benzo[b]thiophenes bearing different substituents at C-2 has been developed from N,N-diethyl O-3-halophenylcarbamates. The key steps are an ortho-lithiation reaction, which gives rise to 3-halo-2-sulfanylphenol derivatives, and a electrophilic cyclization. The subsequent functionalization of the prepared halobenzothiophenes allows the access of a wide variety of 2,3,7-regioselectively functionalized benzo[b]thiophenes in good overall yields.

Synthesis of 4-functionalized-1H-indoles from 2,3-dihalophenols.

A new synthesis of 4-halo-1H-indoles has been developed from easily available 2,3-dihalophenol derivatives. The key steps are Smiles rearrangement and a one-pot or stepwise Sonogashira coupling/NaOH-mediated cyclization. Subsequent functionalization allows access to a wide variety of 2,4- or 2,3,4-regioselectively functionalized indoles.

Regioselective synthesis of 4- and 7-alkoxyindoles from 2,3-dihalophenols: application to the preparation of indole inhibitors of phospholipase A2.

An efficient and regioselective synthesis of 4- and 7-alkoxyindoles has been developed from commercially available starting materials such as 3-halophenols and 3-chloroanisole. Directed ortho-metalation followed by two palladium-catalyzed processes, a Sonogashira coupling and a tandem amination/cyclization reaction, allows the synthesis of regiochemically pure 4- and 7-substituted indoles. This strategy has been successfully applied to the preparation of 2-[3-(2-amino-2-oxoacetyl)-1-benzyl-2-ethyl-1H-indol-4-yloxy]acetic acid (LY315920), a known inhibitor of phospholipase A2.