Selective Sonogashira Couplings in 1,2,4,5-tetrazine derivatives

1,2,4,5-Tetrazines are six-membered heterocyclic compounds in which the four nitrogen atoms are displayed in a symmetric fashion. Their reactivity is quite different from other heterocyclic aromatic systems due to its unique electron-withdrawing character, comparable to tetra-nitrobenzene. 1 In particular, 1,2,4,5- tetrazines are known to take part in [4+2] inverse-Diels–Alder cycloaddition processes which efficiently lead to the construction of substituted pyridazine systems that are important in drug development and biomarker applications. 2 However, the electronic character of 1,2,4,5-tetrazines hampered the development of 3- ethynyl- and 3,6-diethynyl-1,2,4,5-tetrazine derivatives for molecular electronic applications, proved by the scarcity of examples found in the literature. 3 Herein, we describe the synthesis and characterization of two novel ethynyl-based 1,2,4,5-tetrazine derivatives. Synthesis of 3,6-(4-bromophenyl)-1,2,4,5-tetrazine precursor (1) was achieved in good yield by Pinner’s method, starting from 4-bromobenzonitrile. Despite its low solubility in common organic solvents, this precursor was found to react smoothly under typical Sonogashira coupling conditions to selectively afford the 3-ethynyl (2) and 3,6-diethynyl (3) protected derivatives (Figure 1). Reaction conditions were evaluated in order to provide the best yields and to promote selectivity of the mono- or disubstituted ethynyl derivatives. Finally, deprotection was achieved affording, in the case of compound 3, an unprecedented 3,6- diethynyl-1,2,4,5-tetrazine compound. Time-Dependent Density Functional Theory (TDDFT) calculations for both deprotected ethynyl derivatives were used to simulate electronic spectra. A deep knowledge of the relevant electronic transitions involved and quantitatively satisfactory results of the calculated electronic excitations in comparison with experimental data were obtained.

Relatório da prática de ensino supervisionada realizado no Agrupamento de Escolas nº 4 de Évora - EB 2,3 Conde de Vilalva e Escola Secundária André de Gouveia, em ensino de educação física nos ensinos básico e secundário

O presente relatório surge como um complemento à minha Prática de Ensino Supervisionada, realizada no ano lectivo de 2009/201O, visando essencialmente a reflexão e documentação do trabalho por mim desenvolvido ao longo deste ano. A minha Prática de Ensino Supervisionada debruçou-se sobre a disciplina de Educação Física, e decorreu na Escola EB 2,3 Conde de Vilalva, onde leccionei a disciplina a uma turma de 8° ano, e na Escola Secundária André de Gouveia, tendo leccionado a disciplina a um 12° ano. Durante este mesmo ano lectivo, leccionei ainda entre 8 intervenções a uma turma do 1° Ciclo de Ensino Básico, 1° ano; e 9 intervenções a uma turma do 2° Ciclo de Ensino Básico, o 5° ano. ABSTRACT: This document comes as a complement to my Supervised Teaching Practice, held in the 2009/201O academic year, aiming primarily to reflection and documentation of the work developed throughout this year. My Supervised Teaching Practice was focused on the discipline of Physical Education, and held at EB 2,3 Conde de Vilalva where I taught a class in 8th grade, and in high school André de Gouveia, where I taught the discipline to a class in 12th grade. During that same academic year, I taught between 8 and 1O interventions with a class of 1st cycle of education, 1st grade, and with a class of 2nd cycle of education, a 5th grade.