Switchable Brønsted acid-catalyzed ring contraction of Cyclooctatetraene oxide towards the enantioselective synthesis of Cyloheptatrienyl-substituted homoallylic Alcohols and Oxaborinanes

The ability of cyclooctatetraene oxide to undergo two sequential ring contraction events under mild conditions, using Brønsted acid catalysis, has been studied in detail. We have found that the selectivity can be controlled by the acidity of the catalyst and by the temperature, being able to obtain selectively either the cycloheptatriene carbaldehyde product, arising from a single ring-contraction event, or phenylacetaldehyde that is formed after a second ring contraction process. A complete mechanistic picture of the reaction and a rationale behind the influence of the catalyst is provided based on both experimental and computational data. Finally, this acid-catalyzed ring contraction has been coupled with an in situ enantioselective allylation reaction, delivering enantioenriched cycloheptatrienyl-substituted homoallylic alcohols when it is carried out in the presence of a chiral phosphoric acid catalyst. These homoallylic alcohols have also been converted into enantioenriched oxaborinanes through copper-catalyzed nucleophilic borylation/cyclization protocol

Organocatalytically Generated Donor − Acceptor Cyclopropanes in Domino Reactions. One-Step Enantioselective Synthesis of Pyrrolo[1,2 ‑ a ]quinolines

An easy and straightforward procedure has been developed for the synthesis of highly enantioenriched pyrrolo-[1,2-a]quinolines through a one-pot process that comprises a domino cyclopropane ring opening/aza-Michael/aldol reaction followed by acid-promoted lactamization. The key feature of the synthetic approach relies on the ability of conveniently functionalized cyclopropaneacetaldehydes to undergo organocatalytic activation by a chiral secondary amine that enables the catalytic generation of a donor acceptor cyclopropane. This intermediate has the potential to undergo a ring opening that generates an electrophilic alpha,beta-unsaturated iminium ion that subsequently reacts through the already mentioned domino sequence and in which stereochemical information is very efficiently transferred from the amine catalyst to the final products. Moreover, one of the alkoxycarbonyl moieties can be easily removed by standard hydrolysis/decarboxylation, providing access to the target adducts as single stereoisomers.This research was supported by the Spanish MINECO (FEDER-CTQ2014-52107-P), the Basque Government (Grupos IT328-10), and UPV/EHU (fellowship to E.S. and UFI QOSYC 11/22). Membership in the COST action CM1407 (NatChemDrugs) is also acknowledged

ANALISIS KESESUAIAN LAHAN PERMUKIMAN BERDASARKAN RENCANA TATA RUANG WILAYAH (RTRW) DI KABUPATEN MINAHASA TENGGARA (STUDI KASUS : KECAMATAN RATAHAN)

Lahan untuk permukiman perlu memperhatikan kondisi fisik lingkungan antara lain topografi, morfologi, kelerengan dan jenis tanah. Beragam kasus kerugian ataupun korban yang terjadi karena penyimpangan atau ketidaksesuaian penggunaan lahan yang menyalahi tingkat kemampuan lahannya. Keadaan tersebut menyebabkan perlunya analisis kesesuaian lahan permukiman untuk mengetahui kesesuaian lahan yang akan diperuntukan guna pengembangan permukiman. Tujuan penelitian ini yaitu mengkaji perkembangan lahan permukiman di Kecamatan Ratahan berdasarkan data citra dan analisis kesesuaian peruntukan lahan permukiman RTRW terhadap arahan kesesuaian lahan. Metode analisis pada penelitian ini menggunakan metode analisis spasial skoring dan overlay dengan Sistem Informasi Geografis (SIG). Hasil yang diperoleh dari penelitian ini adalah perkembangan permukiman Kecamatan Ratahan tahun 2003-2019 sebesar 41,61 Ha. Hasil penelitian kesesuaian peruntukan lahan permukiman terhadap arahan kesesuaian lahan Kecamatan Ratahan terdapat kriteria sesuai (A) sebesar 127,43 ha atau 2,07%, kriteria sesuai (B) sebesar 2.421,84 ha atau 39,29%, kriteria tidak sesuai (A) sebesar 2,59 ha atau 0,04%, kriteria tidak sesuai (B) sebesar 3.611,62 ha atau 58,60%.Kata kunci: Kesesuaian Lahan, Permukiman, Rencana Tata Ruang Wilayah, SI

Sudden cardiac arrest on the football field of play - highlights for sports medicine from the European Resuscitation Council 2015 Consensus Guidelines

The European Resuscitation Council (ERC) 2015 Guidelines for Resuscitation were published recently. For the first time, these guidelines included a subsection on ‘cardiac arrest during sports activities’ in the section dealing with cardiac arrest in special circumstances, endorsing both the importance and unique nature of this form of cardiac arrest. This paper reviews four critical areas in the management of sudden cardiac arrest in a football player: recognition, response, resuscitation and removal from the field of play. Expeditious response with initiation of immediate resuscitation at the side of a collapsed player remains crucial for survival, and chest compressions should be continued until the automated external defibrillator (AED) has been fully activated, so that the sideline medical team response to the side of a non-contact collapsed player on the field of play, with AED and defibrillation, occurs within a maximum of2 min from collapse.http://bjsm.bmj.comhb201

Brønsted Acid versus Phase-Transfer Catalysis in the Enantioselective Transannular Aminohalogenation of Enesultams

We have studied the enantioselective transannular aminohalogenation reaction of unsaturated medium-sized cyclic benzosulfonamides by using both chiral Brønsted acid and phase-transfer catalysis. Under optimized conditions, a variety of bicyclic adducts can be obtained with good yields and high enantioselectivities. The mechanism of the reaction was also studied by using computational tools; we observed that the reaction involves the participation of a conformer of the nine-membered cyclic substrate with planar chirality in which the stereochemical outcome is controlled by the relative reactivity of the two pseudorotational enantiomers when interacting with the chiral catalyst

Organocatalytic Enantioselective Vinylcyclopropane-Cyclopentene (VCP-CP) Rearrangement

We have demonstrated that the catalytic and enantioselective vinylcyclopropane-cyclopentene rearrangement can be carried out on (vinylcyclopropyl)acetaldehydes through activation via enamine intermediates. The reaction makes use of racemic starting materials that, upon ring opening facilitated by the catalytic generation of a donor-acceptor cyclopropane, deliver an acyclic iminium ion/dienolate intermediate in which all stereochemical information has been deleted. The final cyclization step forms the rearrangement product, showing that chirality transfer from the catalyst to the final compound is highly effective and leads to the stereocontrolled formation of a variety of structurally different cyclopentenes

Mcr-als Applied To The Quantitative Monitoring Of The Electrodegradation Process Of Atrazine Using Uv Spectra: Comparative Results With Hplc-dad As A Reference Method

Electrodegradation of atrazine in water was performed using homemade (PA and PB) and purchased (PC) boron-doped diamond anodes. The degradation was monitored off-line by analyzing total organic carbon and high performance liquid chromatography with diode array detector (HPLC-DAD) and at-line by UV spectroscopy. The spectra were recorded every 2 min. The rank deficiency problem was resolved by assembling an augmented column-wise matrix. HPLC was employed to separate the original and byproducts degradation components. Aiming the same goal, multivariate curve resolution - alternating least squares (MCR-ALS) was applied to resolve the UV spectroscopic data. Comparison between HPLC and MCR-ALS separations is presented. By using MCR-ALS the spectra of atrazine and two byproducts were successfully resolved and the resulted concentration profiles properly represented the system studied. The ALS explained variance (R-2) for PA, PB and PC was equal to 99.99% for all of them and the lack of fit for PA, PB and PC were 0.39, 0.34 and 0.54 respectively. The correlation (R) between the recovered and pure spectra were calculate for each electrodegradation, validating the MCR-ALS results. The average R was equal to 0.997. The spectral and concentration profiles described with this new approach are in agreement with HPLC-DAD results. The proposed method is an alternative to classical analyses for monitoring of the degradation process, mainly due to the simplicity, fast results and economy.39213714

DOMINANDO A QUÍMICA

O recurso foi desenvolvido como meio de fixação de conhecimentos sobre os conteúdos geometria molecular e o modelo da repulsão do par de elétrons no nível de valência (RPENV), objetivando estabelecer uma aprendizagem relevante através do ensino lúdico para estudantes do ensino médio. O recurso didático Dominando a Química demonstrou equilíbrio de conceitos importantes na aquisição de conhecimentos presentes no processo educativo e o caráter lúdico. Pela melhora no acerto de algumas respostas, maior facilidade em compreender os conteúdos relacionados à geometria molecular, reconhecer as geometrias moleculares, como também na vontade de superar os desafios propostos pelo jogo. E, adicionalmente, analisado pela motivação e esforço na participação ativa dos alunos, a qual foi permitida pelo ambiente descontraído, imune da pressão do erro e também pelo espaço favorável à troca de conhecimentos. Quando se argumenta que o ensino de química é apenas uma atividade de memorização, os recursos didáticos e atividades lúdicas vêm para mostrar que existe uma alternativa diferente e o Dominando a Química traz essa percepção de forma objetiva. Por fim, o que tornou a aplicação significativamente satisfatória foi presenciar que todos os estudantes estavam envolvidos e estimulados a participarem, sendo gratificante verificar que eles aprenderam novas geometrias, sanaram dúvidas e levantaram questionamentos sobre o recurso