Ion-exchange resin as a new tool for characterisation of coordination compounds and MOFs by NMR spectroscopy

1H and 13C NMR spectroscopy is used to investigate the organic constituents of metal complexes, MOFs and coordination compounds synthesised under solvothermal and precipitation conditions. The elucidation of the ligands in paramagnetic compounds bearing Cu2+(d9), Gd3+ (f7), Eu3+ (f6), Fe3+(d5), ions after treatment with a cationic exchange resin is possible. We prove the efficiency of two post-synthesis linker modifications on diamagnetic IRMOF-3 Zn2+ (d10) with ethyl isocyanate and benzyl bromide

Oxidation of mono-phenols to para-benzoquinones: a comparative study

The oxidation of mono-phenols to para-benzoquinones is of continuing interest due to the existence of numerous natural products containing this structural unit. The chemical reactivity of para-benzoquinones is also noteworthy, as oxidants and dienophiles in the Diels-Alder reaction. We have used for quite some time now, molecular oxygen and catalysis with [CoII(salen)] as the oxidation procedure, but felt the need for other oxidants and conditions to be of use with different phenol substrates. We now present our results on this important oxidation with a variety of oxidants, using eleven mono-phenols as substrates. The oxidants tested are cobalt, nickel, copper and vanadyl metals, with a selection of different salen type ligands. Completing this study we also investigated the use of hydrogen peroxide, OXONE®, dimethyl dioxirane and iodoxybenzoic acid

The Diels-Alder reaction of para-benzoquinones under Lewis acid catalysis conditions and microwaves the effect

In this work it was done the studies of the Diels-Alder reactions of the parabenzoquinones 2,5-dimethyl-para-benzoquinone (A1), 2,6-dimethyl-parabenzoquinone (A2) and thymoquinone (A3) with the dienes cyclopentadiene (B1), 2,3- dimethyl-1,3-butadiene (B2), isoprene (B3), trans-piperylene (B4) and 1- vinylcyclohexene (B5) (Figure I) under catalysis conditions employing as catalyst a mixture of Aerosil® silica and iron chloride (III). The amount of silica used was equimolar with respect to para-benzoquinones, and the iron chloride was employed in catalytic amounts of 4 mol% and 10 mol%. Under these catalysis conditions it was observed the reduction of the reaction times and a significant increase in yield for all the Diels-Alder reactions studied when compared to results obtained when the same reactions were carried out at room temperature and absence of catalysis. In the case of the Diels-Alder reaction of 2,6-dimethyl-para-benzoquinone (A2) with unsymmetrical dienes isoprene (B3), trans-piperylene (B4) and 1-vinylcyclohexene (B5), under catalytic conditions it was observed the reversal of the regioselectivity of these reactions when compared to the regioselectivities obtained for these reactions performed in the absence of catalysis... (continue)Financiadora de Estudos e ProjetosNo presente trabalho foram feitos estudos das reações de Diels-Alder 2,5- dimetil-para-benzoquinona (A1), 2,6-dimetil-para-benzoquinona (A2) e timoquinona (A3) com o ciclopentadieno (B1), 2,3-dimetil-1,3-butadieno (B2), isopreno (B3), transpiperileno (B4) e 1-vinilcicloexeno (B5) (Figura I) nas condições de catálise com a mistura de sílica aerosil® (SiO2 Aerosil®) e cloreto de ferro (III) (FeCl3) catalítico (4 mol% e 10 mol%). Foi observada a redução dos tempos reacionais e o aumento significativo dos rendimentos de todas as reações, quando comparados aos resultados obtidos para estas reações realizadas em temperatura ambiente e ausência de catálise em diclorometano (CH2Cl2). No caso das reações de Diels-Alder da 2,6-dimetil-para-benzoquinona (A2) com os dienos não simétricos B3, B4 e B5 verificou-se que houve a inversão da regiosseletividade destas reações quando comparadas as regiosseletividades obtidas para estas reações na ausência de catálise... (continua

The diels-alder reaction of p-benzoquinones under microwave effect

In this work it was done a study of the microwave effect on Diels - Alder reaction of the p-benzoquinones thymoquinone (A1), 2,5-dimethyl-p-benzoquinone (A2) and 2,6-dimethyl-pbenzoquinone (A3) with the dienes cyclopentadiene (BB1), 2,3-dimethyl-1,3- butadiene (B2B ), isoprene (BB3) and trans-pyperilene (B4B ) (Figure Ι). These reactions were also held under conventional thermal conditions and catalysis with the Lewis acid SnCl4 in order to make a comparison of the results. It was also studied the Diels - Alder reaction in multicomponent version between thymoquinone (A1), trans-2-pentenal and acetamide under microwave effect (Figure ΙΙ). (FORMULA)Regarding the Diels - Alder reaction between p-benzoquinones (A1 - A3) and dienes (BB1 - B4B ) it was observed a reduction of the reaction time, obtaining higher yields and less formation of by - products, all in comparison with the results of the same reactions performed under thermal conventional condition and catalytic condition with SnCl4. This work also involved the study of the microwave effect on Diels - Alder reaction between cyclopentadiene (BB1) and mono-oximes dienophiles C1, C2 and C3 (Figure ΙΙΙ). These reactions had already been carried out in our laboratory, but under conventional thermal and catalytic conditions (Lewis acids). Under such conditions, the mono-oxime starting material was recovered, or a complex mixture of polymerization products was formed. (FORMULA)The reactions of compounds C1, C2 and C3 with cyclopentadiene (BB1) under microwave effect showed similar results with those that were obtained when these reactions were carried out under conventional thermal and catalytic conditions, thus leading to recovery of the mono-oxime starting material or a complex mixture of products which could not be identified.Financiadora de Estudos e ProjetosNeste trabalho foi feito um estudo do efeito das microondas sobre a reação de Diels - Alder das p-benzoquinonas timoquinona (A1), 2,5-dimetil-p-benzoquinona (A2) e 2,6-dimetil-p-benzoquinona (A3) com os dienos ciclopentadieno (B1), 2,3-dimetil-1,3-butadieno (B2), isopreno (B3), transpiperileno (B4) (Figura Ι). Estas reações foram realizadas também sob condições térmicas convencionais e de catálise com o ácido de Lewis, SnCl4, com intuito de se fazer a comparação dos resultados. (FORMULA) Foi estudada também a reação de Diels - Alder em versão multicomponente da timoquinona (A1) com o trans-2-pentenal e acetamida (Figura ΙΙ) sob efeito de microondas. (FORMULA) Em relação à reação de Diels - Alder das p-benzoquinonas (A1 - A3) com os dienos (BB1 - B4) foram observados uma redução dos tempos de reação, obtenção de maiores rendimentos e, portanto menor formação de subprodutos quando comparados com os resultados obtidos para as mesmas reações realizadas sob condições térmicas convencionais e sob condições de catálise com SnCl4. Este trabalho envolveu também o estudo do efeito de microondas sob a reação de Diels - Alder entre o ciclopentadieno (B1B ) e os dienófilos mono-oximas C1, C2 e C3 (Figura ΙΙΙ). Estas reações já haviam sido realizadas em nosso laboratório, porém sob condições térmicas convencionais ou de catálise com ácidos de Lewis. Sob tais condições obteve-se ou a recuperação do dienófilo de partida ou a uma mistura complexa de produtos de polimerização. (FORMULA) As reações dos compostos C1, C2, e C3 com ciclopentadieno (BB1) sob efeito de microondas mostraram resultados semelhantes a aqueles obtidos para as mesmas reações realizadas sob condições térmicas convencionais e de catálise com ácidos de Lewis, levando assim a recuperação do material de partida ou a uma mistura complexa de produtos, os quais não puderam ser identificados

A reação de Diels-Alder no início do século vinte um

The Diels-Alder reaction continues to be the premier method for the construction of complex organic molecules. In the last 10 years many developments have been introduced, and have led to increased utility of this reaction. In this review we present some of these novelties, which are of fundamental importance in organic synthesis