Flavia M. da Silva

Desenvolvimento sustentável e química verde

The world is in a process of awakening with respect to the environment. Our society has started to recognize that the environment is one of our largest resources and has begun legally enforce its protection. In Brazil, the environmental law is constitutionally guaranteed. International treaties have been signed, amongst them the Agenda 21 which is a commitment to sustainable development. Green Chemistry is a strategy that helps make this commitment. The literature presents many examples of studies of the application of Green Chemistry philosophy. In this paper we will present some points that we believe to be important and promising.

Organic reaction in water. Part 3¹: diastereoselectivity in Michael additions of thiophenol to nitro olefins in aqueous media

Tiofenois reagem com nitro olefinas em meio aquoso dando os correspondentes nitro-sulfetos em 58 - 95 % de rendimento. Este processo leva a formacao, predominante, de produtos anti. Para o caso da nitro olefina ciclica 1-nitro-ciclo-hexeno e observada unicamente a formacao de cis-1-nitro-2-(tio-fenil)-ciclo-hexano. Esta metodologia e interessante porque utiliza-se agua como solvente levando a minimizacao do custo, diminuindo os problemas de toxidez e poluicao ambiental

Coiodação de alquenos com nucleófilos oxigenados: reações intermoleculares

A review on the electrophilic addition of iodine to alkenes in the presence of oxygen containing nucleophiles (cohalogenation reaction) is presented. The intermolecular reactions are discussed with emphasis in methods of reaction and synthetic applications of the resulting vicinal iodo-functionalized products (iodohydrins, b-iodoethers and b-iodocarboxylates).

Cohalogenation of limonene, carvomenthene and related unsaturated monoterpenic alcohols

Cohalogenation of (R)-limonene and (R)-carvomenthene with I2/H2O/Cu(OAc)2·H 2O in aqueous dioxane followed by base treatment produced stereospecifically the corresponding trans-epoxides. Same methodology of cohalogenation applied to related monoterpenic unsaturated alcohols produced pinol derivatives [from (5R)-cis-carveol and (S)-a-terpineol] or iodohydrins [from (S)-perillyl alcohol and (5R)-trans-carveol].

Reações orgânicas em meio aquoso

The use of water as solvent in organic reactions has been uncommon for several reasons, among them the low solubility of the reactants, the incompatibility of the intermediates with water, and the competition between the desired reaction and hydrolysis. Breslow in 1980, demonstrated that the hydrophobic effect accelerates Diels-Alder reactions and gives a high endo/exo selectivity. Since then, many other reactions were studied in this medium, and below we show the principal results. Besides the academic interest, human and economic aspects are included in this study. Water as a solvent minimizes environmental impact, costs and increases operational safety.

Michael Additions of Thiocompounds to AB -Unsaturated Carbonyl Compounds in Aqueous Media: Stereoselectivity with Unambiguous Characterization by NMR

The reactions of crotonaldehyde (8) with thiophenol (2) and benzalacetone (10) with ethane-1,2-dithiol (11) yield Michael addition products. The reactions of thiophenol (2) with (R)-carvone (13) and (S)-perillaldehyde (15) lead to (2S,3R,5S)-5-isopropenyl-2-methyl-3-(phenylthio)cyclohexanone (14) and (1R,2R,4S)-4-isopropenyl-2-(phenylthio)cyclohexanecarbaldehyde (16), respectively. An unambiguous elucidation of the stereochemistry of 14 and 16 by NMR is also presented.

FUNCTIONALIZED PINOLS: 13C AND 1H NMR SPECTRA ASSIGNMENTS AND STRUCTURES

Aqueous cohalogenation reactions of cis-carveol and of α-terpineol afford respectively the 2, 6-dimethyl-6-iodomethyl-7-oxabicyclo[3.2.1]oct-2-ene and 2, 6, 6-trimethyl-7-oxabicyclo[3.2.1]octan-2-ol. Previous structural analysis involving such functionalized pinols have lacked justification of the proposed relative configuration of the substituents and detail of the 1H and 13C NMR spectra assignments. Thus, a full structure and NMR analysis for these two bicyclic compounds are presented by way of 2D NMR experiments, 1H spectra simulations and AM1 calculations.