Reação de condensação do glicerol com compostos carbonílicos : síntese, caracterização e aplicação em cristais líquidos

Este trabalho buscou desenvolver e estudar as transformações químicas do glicerol através das reações de condensação com compostos carbonílicos, e a posterior modificação desses produtos para a obtenção de materiais funcionais. Para isto, nesta pesquisa primeiramente estudou-se as reações de acetalização e cetalização, com glicerol, aldeídos e cetonas aromáticas, empregando o aquecimento convencional e aquecimento por irradiação de micro-ondas. Utilizaram-se também para esta rota sintética, catalisadores homogêneos, como por exemplo, ácido sulfúrico e ácido p-tolueno sulfônico, assim como catalisadores heterogêneos, como, por exemplo, carvão ativo, zeólitas com diferentes tamanhos de poros, alumina sulfatada e sílica sulfatada. Desta forma, observa-se que independente do tipo de aquecimento ou catalisador para as reações que empregavam aldeídos, formou-se uma mistura com quatro produtos isoméricos, um anel de 5 átomos cis e trans (1,3-dioxolano) e um anel de 6 átomos cis e trans (1,3-dioxano). Quando o catalisador empregado era homogêneo, tem-se que o anel de 6 átomos era majoritário nestas reações e quando o catalisador empregado era heterogêneo, tem-se que o anel de 5 átomos era majoritário. Em todos os experimentos realizados a proporção dos isômeros formados foi de aproximadamente 60: 40. Os testes catalíticos realizados para cetonas aromáticas não apresentaram resultados em virtude da baixa reatividade das cetonas nas reações estudadas. Os experimentos catalíticos de ciclização também foram realizados com aldeídos e cetonas alifáticas, onde o aquecimento utilizado foi somente o convencional na presença dos catalisadores heterogêneos sílica sulfatada e alumina sulfatada, além do catalisador homogêneo ácido p-tolueno sulfônico. No final destes experimentos ao serem empregados aldeídos alifáticos obteve-se uma maior seletividade dos aneis de 5 átomos quando o catalisador heterogêneo era empregado e de 6 átomos quando o catalisador homogêneo era empregado. Também verificou-se quando se empregava as cetonas alifáticas, obtia-se uma seletividade superior a 95 % para o anel de 5 átomos. A segunda parte deste trabalho foi voltada para as reações de derivatização do solketal, que é o produto obtido da condensação do glicerol com a propanona disponível comercialmente, visando modificações nas hidroxilas primárias do Solketal, através de reações de alquilação e hidrólise, deixando a hidroxila secundária disponível para ser funcionalizada posteriormente. Desta forma foram realizadas reações de transformação do solketal em compostos com novas funcionalidades. Através da reação de alquilação obtiveram-se compostos apresentando o grupo alila, citronelila e benzila. Esses intermediários são importantes na preparação de materais funcionais, tais como cristais líquidos poliméricos. A parte final deste trabalho foi voltada para a síntese de compostos funcionais com propriedades líquido-cristalinas. Foi sintetizado um monômero final a partir do solketal através de reações de transformação desse intermediário. O composto final na forma de monômero apresentou propriedades líquido-cristalinas com mesofase esmética C, e uma faixa de temperatura de 23 °C. Os resultados das diferentes reações do glicerol estudadas neste trabalho são promissores, com aplicação direta em materiais funcionais líquido-cristalinos, quirais e géis. Assim sendo, com este estudo demonstrou-se que as reações pesquisadas podem ser utilizadas como novas metodologias sintéticas para o aproveitamento do glicerol excedente.This work aimed to develop and study the chemical transformations of glycerol through condensation reaction with carbonyl compounds, and its subsequent use in the field of functional materials. To order to achieve this, the first study in this research is the reaction of acetalization and ketalization, glycerol, aromatic aldehydes and ketones, using conventional heating and heating by microwave irradiation. For this synthetic route it was also used, homogeneous catalysts such as sulfuric acid and p-toluene sulfonic acid, as well as heterogeneous catalysts, for example, activated carbon, zeolites with different pore sizes, sulfated alumina and silica sulphated. This way, it can be observed that independent of the type of heat or catalyzer used for reactions employing aldehydes formed a mixture of four isomeric products a ring of 5 atoms cis and trans (1,3-dioxolane) and a ring 6 atoms cis and trans (1,3-dioxane). When the catalyzer employed was homogeneous, the ring of 6 atoms is in the majority of these reactions and when the heterogeneous catalyst was employed the ring has 5 atoms in majority. In all experiments the ratio of isomers formed was approximately 60: 40. The catalytic tests for aromatic ketones showed no results due to the low reactivity of ketones in the studied reactions. The catalytic cyclization experiments were also conducted with aliphatic aldehydes and ketones, where only conventional heating was used in the presence of heterogeneous catalysts sulfated and sulfated silica alumina. At the end of these experiments the application of aliphatic aldehydes gave higher selectivity to the 5 atoms of the rings when the heterogeneous catalyst was employed and 6 atoms when the homogeneous catalyst was employed. Also it has been found that when employing aliphatic ketones, it was obtained a higher selectivity at 95% for 5 ring atoms. The second part of this work has been directed to derivatizing reactions solketal, which is the product obtained by condensation of glycerol with propanone commercially available, seeking changes in the primary hydroxyls Solketal through alkylation and hydrolysis reactions, leaving the secondary hydroxyl available to be subsequently functionalized.Thus solketal transformation reactions were performed on compounds with new features. By alkylation reaction there were obtained Compounds showing the allyl group, citronelila and benzyl. These are important intermediates in the preparation of functional materais such as polymeric liquid crystals. The final part of this study was aimed to synthesize functional compounds with liquid crystalline properties. A final monomer was synthesized from solketal using those intermediary transformation reactions. The final compound as a monomer liquid crystalline properties presented with a smectic C mesophase, and a 23 ° C temperature range. The results of the different glycerol reactions studied in this work are promising, with direct application in liquid-crystalline functional materials, chiral and gels. Thus, this study demonstrated that the investigated reactions can be used as new synthetic methods for the use of excess glycerol

Efeito do processamento da semente de tungue para obtenção do óleo na síntese de biodiesel

O Brasil possui uma grande diversidade de plantas oleaginosas espalhadas em diferentes regiões do território. Dentre as diversas oleaginosas conhecidas, destaca-se o tungue (aleuritis fordii), cultivado no Rio Grande do Sul, com vantagens tanto em rendimento de óleo como custo de implantação da cultura. O óleo utilizado para a síntese de biodiesel etílico pode ser bruto ou refinado. Assim, o objetivo deste trabalho é desenvolver uma metodologia viável, comparando as diferentes origens de óleo utilizadas na síntese de biodiesel etílico de tungue

Condensation reaction of glycerol and carbonyl compounds : synthesis, characterization, and derivatization for liquid crystals

Condensation reactions of glycerol with aldehydes and ketones were performed under thermal heating and microwave irradiation regimes. Homogeneous and heterogeneous catalysts were tested in both conditions. A silica sulfated (SiO2–SO3H) heterogeneous catalyst demonstrated the best performance relative to a selectivity of >95% in favor of 5-membered ketals. For acetals, preference in favor of 5-membered or 6-membered functional groups depends on the nature of the catalyst. Homogenous catalysts favor the more stable 6-membered acetals, whereas heterogeneous catalysts favor the less stable 5-membered acetals. However, the isomer ratios in the acetalization reaction are too low, and hence the reaction cannot be used in a synthetic plan for functional materials. Ketalization processes mediated by SiO2–SO3H show a high selectivity in favor of a 5-membered ring (1,3-dioxolane). The scope of condensation was tested with different ketones. A mechanism for heterogeneous catalysis related to the selectivity in the cyclization process is presented herein. Solketal, a commercial product, was also obtained by a condensation reaction of glycerol and propanone, and showed a high selectivity in favor of 1,3-dioxolane. It was transformed to potential allylic and chiral intermediates. A mesogenic core was connected to the organic framework of glycerol to produce a monomer liquid crystal material with a stable smectic-C mesophase

Síntese de biodiesel etílico de tungue utilizando catalisadores alcalinos

A grande diversidade de plantas oleaginosas distribuída por todo o território nacional e a auto-suficiência brasileira na produção de etanol, impulsiona a pesquisa de produção de biodiesel etílico. Deste modo, o desenvolvimento de metodologia para a síntese de biodiesel etílico de tungue (Aleuritis fordii) é bastante favorável, pois o cultivo desta oleaginosa se faz em pequenas propriedades rurais, com colheita manual e sem mecanização, inserindo a agricultura familiar no processo de produção de biocombustíveis. Assim, o objetivo deste trabalho foi desenvolver uma metodologia viável para a síntese de biodiesel etílico a partir do óleo de tungue, empregando catalisadores alcalinos convencionais, NaOH e KOH, introduzindo uma melhor separação do biodiesel de seus co-produtos

The genus Calea L.: a review of isolated compounds and biological activities

The approximately 125 species of the genus Calea L. (Asteraceae) are distributed throughout tropical and subtropical regions of the Americas. Some species have medicinal properties. Based on popular knowledge, different phytochemical and pharmacological activities have been the focus of research. This review aims to provide an overview of the current state of knowledge of medicinal uses, chemical constituents, and pharmacological activities of Calea species. Phytochemical and pharmacological studies have been performed on 37 species to date. Aerial parts, leaves and stems of these plants have been tested for several biological effects including antinociceptive, vasodilator, cytotoxic and antimicrobial activities. Extracts obtained from plants of the genus Calea have also been assayed for potential antiparasitic effects, especially for antiplasmodial, leishmanicidal, acaricidal and trypanocidal activities. Phytochemical investigations have confirmed that Calea species are rich in sesquiterpenes, chromenes, chromanones, flavonoids and other chemical compounds less attractive from the point of view of molecular diversity. This review confirms that certain Calea spp. enjoy widespread popular use in the treatment of infections, and the observed antiparasitic activities can provide new insights for further investigations on isolated compounds. </p

Phytochemical investigation, antinociceptive activity and cytotoxicity of crude extracts of Calea uniflora Less.

International audienceCalea uniflora Less. is a medicinal plant used in the treatment of inflammation and haematomas in southern Brazil. The aim of this study was to investigate the antinociceptive effects and cytotoxicity of C. uniflora. Regarding phytochemical evaluation, the crude extracts of plant were analysed by high-performance liquid chromatography (HPLC). Antinociceptive activities utilised models on chemical and thermal stimuli in vivo. To evaluate cytotoxic activity, the 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide method (MTT test) was utilised in vitro. Phytochemical analyses verified the presence of flavonoids and sesquiterpenes. Regarding antinociceptive activity, the models produced significant results that correspond to chemical at doses of 100 and 300 mg/kg of the crude extract as compared to the control groups, respectively. The rota rod model showed satisfactory results, since the extract did not cause motor incoordination and sedation in this experiment. In the in vitro cytotoxic tests, the crude extracts and ethyl acetate and butanolic fractions produced IC50 values greater than 58 &micro;g/mL with the HaCaT lineage and 48 &micro;g/mL with the B16-F1 lineage; thus, these values did not produce cytotoxic effects. According to these results, flavonoids and alkaloids were found in C. uniflora extracts. Pharmacological activities were also detected as reported by the local population that uses this plant in traditional medicine, especially antinociceptive and cytotoxic activities. Key words: Antinociception, cytotoxicity, phytochemistry, Calea uniflora, medicinal plant

Risk of COVID-19 after natural infection or vaccinationResearch in context

Summary: Background: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. Methods: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Findings: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Interpretation: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. Funding: National Institutes of Health