Köln, Universiẗat, Diss., 2002.

Conjugate addition reactions are one of the most widely used carbon-carbon bond forming reactions in organic synthesis. This reaction can form a chiral center and can be used for the synthesis of structurally complex compounds. Until now it has been necessary to use a chiral heavy metal catalyst in order to carry out asymmetric addition of aromatic groups to α,b-unsaturated enones via conjugate addition. Recently we have been successful in achieving the same task using an arylboronate as well as a catalytic amount of a chiral substituted binaphthol (BINOL). Using this reaction method great yields and enantioselectivities were achieved when diethyl phenylboronate was added to various enones and when various diethyl arylboronates were added to chalcone. This reaction is exciting because it eliminates the chance of having trace amounts of heavy metals in the final product, which is advantageous in such areas as the pharmaceutical industry.

Conjugate addition reactions are one of the most widely used carbon-carbon bond forming reactions in organic synthesis. This reaction can form a chiral center and can be used for the synthesis of structurally complex compounds. Until now it has been necessary to use a chiral heavy metal catalyst in order to carry out asymmetric addition of aromatic groups to α,b-unsaturated enones via conjugate addition. Recently we have been successful in achieving the same task using an arylboronate as well as a catalytic amount of a chiral substituted binaphthol (BINOL). Using this reaction method great yields and enantioselectivities were achieved when diethyl phenylboronate was added to various enones and when various diethyl arylboronates were added to chalcone. This reaction is exciting because it eliminates the chance of having trace amounts of heavy metals in the final product, which is advantageous in such areas as the pharmaceutical industry.

Regensburg, Univ., Diss., 2009.

Universiẗat, Diss., 2004--Kiel.

<p> A detailed study of the photoaddition of 3-phenylcyclohex- 2-enone and 2,3-dimethylbut-2-ene was undertaken in order to gain mechanistic information of the photochemistry of this enone. Photoadditions of this enone with cyclopentene, norbornene, and but-2-ene were also studied. Sensitization experiments showed that photoaddition with 2,3-dimethylbut-2-ene occurs when triplet sensitizers such as Michler's ketone or 2-acetonaphthone are used. The sensitized reactions are less efficient than the direct irradiation, except at infinite 2,3-dimethylbut-2-ene concentration, when the quantum yields for direct and sensitized processes are the same. This quantitative result may be explained by (a) inefficiency in the energy-transfer process from the sensitizer to enone 0 or (b) two excited states of enone being involved in the direct and sensitized processeso There are evidences that the excited state involved in the direct irradiation could possibly be the second triplet of the enoneo The presence of a higher enone tTiplet (T2) was established by the observed dimerization of norbornene. Cis-trans isomerization of but-2-ene was observed during photoaddition, which could also be attributed to a higher triplet, or to a 1,4-diradical intermediates Quenching studies provided an estimate of the lifetime of the reactive excited state in the direct irradiation. The energies of the electronic states of the enone were estimated from spectroscopic and chemical measurements. The formation of an enoneoolefin 1,4-diradical has been proposed to explain the effect of olefin concentration on the photoaddition. </p> / Thesis / Doctor of Philosophy (PhD)

Na primeira parte desta tese são apresentados os resultados referentes ao desenvolvimento de uma metodologia de &#945;-alquinilação eletrofílica de aldeídos com o reagente de iodo hipervalente TMS-EBX, empregando NaHMDS como base e TBAF. Aldeídos acíclicos foram submetidos a esta transformação e 9 exemplos de álcoois homopropargílicos foram obtidos em rendimentos de 50-81%, após uma etapa de redução com NaBH4. A transformação desenvolvida revelou-se aplicável também com o reagente de iodo hipervalente Ph-EBX e 2 exemplos foram obtidos em 24 e 40% de rendimento. O álcool homopropargílico precursor de um inibidor da bactéria que produz a toxina botulínica foi preparado em uma escala de 5 mmol sem a necessidade de alterar as condições reacionais já otimizadas. Na segunda parte desta tese são apresentados os resultados referentes ao desenvolvimento de uma metodologia para a síntese de cetonas cíclicas e 2-cromanonas &#945;-alquinil-&#946;-substituídas por meio de uma sequência de adição 1,4/alquinilação eletrofílica empregando cumarinas e enonas como material de partida, utilizando o reagente de iodo hipervalente TMS-EBX. Os enolatos foram gerados com sucesso a partir de uma reação de adição 1,4 catalisada por cobre utilizando complexos de alumínio e reagentes de Grignard como fontes nucleofílicas. No total foram obtidos 17 exemplos em 34-89% de rendimento e em alta diastereosseletividade. Realizamos três modificações estruturais visando aumentar a complexidade estrutural dos produtos sintetizados. A reação Click, rea- ção de Sonogashira e redução mediada por NaBH4 foram aplicadas com sucesso. Por fim, na terceira parte desta tese são apresentados os resultados preliminares referentes ao desenvolvimento de uma metodologia de síntese de furanos a partir da acetofenona e do reagente de iodo hipervalente Ph-EBX, empregando NaHMDS comoviii base. A acetofenona foi submetida a esta transformação e uma mistura de furanos di- e trissubstituídos foram obtidos em 49% de rendimento. Um experimento controle demonstrou que a alquinilação do ânion terc-butóxido, em uma reação extremamente rápida, é a principal via de consumo do Ph-EBX e o composto (terc-butoxietinil)benzeno foi obtido em 92% de rendimento. Esta reação lateral é a principal responsável pelo baixo rendimento da reação de síntese dos furanos. / In the first part of this work are presented the results relative to the development of a methodology of &#945;-electrophilic alkynylation of aldehydes with the hypervalent iodine reagent TMS-EBX, employing NaHMDS as base and TBAF. Acyclic aldehydes were submitted to this transformation and 9 examples of homopropargylic alcohols were obtained in 50-81% yield, after a reduction step with NaBH4. The developed transformation proved to be works also with the hypervalent iodine reagent Ph-EBX and 2 examples were obtained in 24 and 40% yield. The homopropargylic alcohol precursor of an inhibitor of bacteria that produces a botulinic toxin was prepared at a 5 mmol scale without change the reaction condition already optimized. In the second part of the thesis are presented the results relative to the development of a methodology for the synthesis of cyclic ketones and 2-chromanones &#945;-alkynyl-&#946;-substituted by the1,4-addition/electrophilic alkynylation sequence using coumarins and enones as a starting material and the hypervalent iodine reagent TMS-EBX. The enolates were generated with success from a Cu-catalyzed 1,4 addition using aluminum complexes and Grignard reagents as nucleophilic source. In total 17 examples were obtained in 34-89% yield and high diastereoselectivity. We carried out three structural modification aiming to increase the complexity of the products synthesized. Click reaction, Sonogashira reaction and reduction promoted by NaBH4 were applied with success. Finally, in the third part of the thesis are presented the preliminary results relative to the development of a methodology for synthesis of furans from acetophenone and the hypervalent iodine reagent Ph-EBX, using NaHMDS as a base. Acetophenone was submitted to this transformation and only one example was obtained in 49% yield in a mixture of di- and trisubstituted furans. A control experimentx showed that the alkynylation of tert-butoxide anion, in an extremely fast reaction, is the main path of consumption of the Ph-EBX reagent and the compound (tert-butoxyethynyl)benzene was obtained in 92% yield. This side reaction is the main responsible for the low yield of the reaction of synthesis of furans.

Techn. Universiẗat, Diss., 2004--Berlin.

A variety of protected enolic forms of 1, 2-cyclohexanedione was prepared as substrates for conjugate addition studies using organocopper reagents. The sequence involved the enol ether preparation via the enolate, alkylation with an organometalic reagent, and oxidative rearrangement with pyridinium chlorochromate followed by the conjugate addition reactions. Protection of 1, 2-cyclohexanedione was achieved by reacting with chloro tert-butyldimethyl silane and subjected to alkylation. Steric problems were encountered and so an alternative protective group the methoxymethyl acetal was prepared and studied. Alkylation of these derivatives was successful; however, the oxidation was problematic and although evidence for rearrangement was observed in one case, it did not provide the desired ketone.

Ce travail traite de l’exploration de la biodiversité des Baeyer-Villiger MonoOxygénases (BVMOs) : des enzymes utilisées en biocatalyse pour la production de lactones optiquement pures à partir de cétones. Pour mettre à bien cet objectif nous avons réalisé, en association avec le Génoscope d’Evry, une sélection de plusieurs centaines d’enzymes couvrant une forte diversité génétique. Après clonage et criblage à haut débit sur plus de vingt substrats différents nous avons obtenus plus de 90 nouvelles BVMOs. Avec ce résultat nous avons triplé le nombre de BVMOs connues dans la littérature. Dans un second temps nous avons étudié l’activité de certaines de ces nouvelles enzymes sur les cétones α,β-insaturées (ou enone), Ces substrats sont peu étudiés en biocatalyse et, lors de la réaction chimique, aboutissent à la formation de nombreux sous-produits. Deux enzymes d’O.batsensis et de P. lavamentivorans se sont révélées être actives aboutissant à la production d’ene-lactone et d’enol-lactone respectivement. La conversion de certaines enones chirales a abouti à des lactones présentant un fort excès énantiomérique.Nous avons ensuite étudié la régio-sélectivité de 35 enzymes issues du criblage sur une série de cétones aliphatiques acycliques. Alors que la formation de l’ester méthylique est très rare, nous avons obtenu des résultats très variés pour la formation de l’ester éthylique allant jusqu’à 80%. Le travail de thèse s’est terminé par le développement d’une cascade enzymatique sur la production d’ester à partir d’alcool secondaire. La cascade implique deux enzymes : une Alcool Déshydrogénase et une BVMO. La cascade est à la fois fonctionnelle et est très efficace. / -