Thesis--Wisconsin. / Vita. Includes bibliographical references.

Thesis advisor: Shih-Yuan Liu / Thesis advisor: Marc Snapper / Organoboron compounds are widely used in organic synthesis and medicinal chemistry. It has been shown that organoboron compounds can undergo a vast quantity of transformations, especially stereospecific reactions. Boron enolates and their reactivity are less explored in the field of organic chemistry. In enolates, boron can be bound to oxygen or carbon. The boron-carbon enolates are of interest for having the potential to engage in stereospecific organoboron chemistry via the stereospecific carbon connected to the boron atom. Two methods of synthesizing boron-carbon enolates are through quaternized and unquaternized boron centers. While quaternized boron-carbon enolates are more studied, unquaternized boron-enolates represent a gap in the field. To date only four unquaternized boron-carbon enolates have been isolated and characterized with only one of the compounds engaging in organoboron chemistry. Herein I report the synthesis, isolation, and characterization of a boron-carbon enolate containing 1,2-azaborine as the organoboron analog. / Thesis (MS) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

No description available.

No description available.

New processes that leads to formation of new carbon-carbon bond (the Michael reaction, the Mannich reaction and alkylation reaction) or carbon-heteroatom bond (á-halogenation, á-hydroxylation and á-amination) on bridged bicyclic ketones such as tropinone and TBON were investigated, utilizing LDA in the deprotonation step. All reactions, in which new carbon-heteroatom bond is formed, were not successful either due to low selectivity and/or yields. In case of new carbon-carbon bond forming processes, careful choice of electrophile (electrophile having the ester group in á-position to leaving group), allows for alkylation of tropinone with moderate yield and good selectivity. Application of new conditions to the aldol reaction of TBON and tropinone (e.g. MgI2 catalyzed aldol reaction), gave new aldol products that were not detected from the lithium enolate chemistry of these ketones. Modification of reaction conditions in case of MgI2 catalyzed aldol reaction provides, in a one pot process, bis-aldol product from TBON in good yield and high selectivity, as a single diastereoisomer. Finally, TBON is used as a suitable scaffold for the synthesis of thiacocaine. The first known synthesis of racemic thiacocaine is presented, via deprotonation of TBON with LDA, as a key step.

New processes that leads to formation of new carbon-carbon bond (the Michael reaction, the Mannich reaction and alkylation reaction) or carbon-heteroatom bond (á-halogenation, á-hydroxylation and á-amination) on bridged bicyclic ketones such as tropinone and TBON were investigated, utilizing LDA in the deprotonation step. All reactions, in which new carbon-heteroatom bond is formed, were not successful either due to low selectivity and/or yields. In case of new carbon-carbon bond forming processes, careful choice of electrophile (electrophile having the ester group in á-position to leaving group), allows for alkylation of tropinone with moderate yield and good selectivity. Application of new conditions to the aldol reaction of TBON and tropinone (e.g. MgI2 catalyzed aldol reaction), gave new aldol products that were not detected from the lithium enolate chemistry of these ketones. Modification of reaction conditions in case of MgI2 catalyzed aldol reaction provides, in a one pot process, bis-aldol product from TBON in good yield and high selectivity, as a single diastereoisomer. Finally, TBON is used as a suitable scaffold for the synthesis of thiacocaine. The first known synthesis of racemic thiacocaine is presented, via deprotonation of TBON with LDA, as a key step.

Orientador: Luiz Carlos Dias / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-16T16:04:10Z (GMT). No. of bitstreams: 1 Pinheiro_SavioMoita_D.pdf: 9633814 bytes, checksum: c4c7b0ac3175d0a710829278dbc19423 (MD5) Previous issue date: 2010 / Resumo: As reações aldólicas com enolatos de boro de metilcetonas quirais contendo o protetor p-metóxi- benzilideno cetal (105 e 106) levaram a obtenção do diastereoisômero com indução 1,5-anti em boas seletividades. A avaliação do processo de dupla-diastereosseletividade da metilcetona 105 mostrou que existe uma influência parcial por parte do aldeído no nível de seletividade. Reações aldólicas com metilcetonas acíclicas 1,2-syn-dissubstituídas contendo os grupos protetores PMB (108) e TBS (107) levaram ao isômero 1,5-anti em baixa seletividade. O emprego das metilcetonas contendo a relação 1,2-anti entre os seus estereocentros mostrou baixos níveis de indução 1,5-anti para a metilcetona 109 e 1,5-syn, para a metilcetona 110, eliminando a possibilidade de competição entre as induções 1,4-syn e 1,5-anti. Com o objetivo de compreender os fatores que controlam a reação aldólica, outros estudos estão em andamento no nosso grupo de pesquisas. / Abstract: We report herein that good to excellent levels of 1,5-anti stereoinduction are obtained in boron enolate aldol reactions of 1,2-syn -alkoxy methyl ketones with achiral aldehydes, when the b-alkoxy protecting group is part of a benzylidene ketal. The strong internal stereoinduction of the b-alkoxy stereocenter of the boron enolates dominates the overall stereochemical outcome of the corresponding aldol addition reactions, leading to the 1,5-anti products with good levels of diastereoselectivities. Even with the use of acyclic a-methyl-b-alkoxy methyl ketones, the b-stereocenter plays a dominant role in determining the sense of 1,5-anti asymmetric induction, although lower levels of diastereoselectivities were obtained. Due to the lower energy difference observed between transition states, it looks like a mismatched relationship case as a competition between 1,4-syn induction from the a-methyl stereocenter and 1,5-anti induction from the b-alkoxy stereocenter. The results showed a predominance of 1,5-induction in competition with 1,4-induction. / Doutorado / Quimica Organica / Doutor em Ciências

Orientador: Luiz Carlos Dias / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-15T23:16:23Z (GMT). No. of bitstreams: 1 SallesJunior_AirtonGoncalves_D.pdf: 4515797 bytes, checksum: ade68b7c48191db164311e6fb23eab41 (MD5) Previous issue date: 2009 / Resumo: Este trabalho relata a síntese total dos ácidos pterídicos A e B. O plano sintético utiliza como etapa-chave a reação aldólica syn com adição anti-Felkin intermediada por enolato de lítio entre a etil cetona a,b-insaturada de geometria Z 5 e o aldeído 4 para obtenção do fragmento C5-C15. Até onde sabemos este é o primeiro exemplo da utilização de um enolato de uma etil cetona a,b-insaturada quiral com geometria Z em uma reação aldólica. Uma eficiente reação de espirocetalização seguida de transformações adicionais conduziu ao ácido pterídico A em 2,9% de rendimento global para 13 etapas e ao ácido pterídico B em 2,8% de rendimento global também para 13 etapas. Em relação às outras sínteses totais, esta rota sintética apresenta um rendimento global comparável, mas chama a atenção pela nova e interessante abordagem na obtenção do fragmento C5-C15 via reação aldólica intermediada por lítio / Abstract: This work describes the convergent stereoselective synthesis of pteridic acids A and B. Our strategy involved a lithium enolate-mediated aldol reaction between ethyl ketone 5 and aldehyde 4 as the key step to set up C5-C15 fragment favoring 1,2-syn anti-Felkin adduct. As far we know, this is the first example of an aldol reaction between a chiral enolate of a (Z) enone and a chiral aldehyde. Efficient spiroketalization followed by additional transformations provided pteridic acids A and B in 2.9% and 2.8% overall yields, respectively. This approach compares very well with previously published routes and attracts attention to the novel and interesting C9-C10 bond construction to obtain C5-C15 fragment / Doutorado / Quimica Organica / Doutor em Ciências

Orientador: Luiz Carlos Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T09:34:22Z (GMT). No. of bitstreams: 1 Oliveira_VandaMariade_M.pdf: 2580285 bytes, checksum: 691d41628333efc92e279be76c7dd14c (MD5) Previous issue date: 2008 / Resumo: O capítulo 1 descreve as reações aldólicas de enolatos de boro de metilcetonas quirais com aldeídos aquirais. Neste trabalho relatamos resultados que sugerem a competição entre a estereoindução 1,4/1,5 na construção da ligação C-C dos adutos de aldol. Os produtos foram obtidos com seletividades que variam de 50:50 a 70:30, e em rendimentos que variaram de 82-95%. O capitulo 2 descreve as reações aldólicas de enolatos de boro de metilcetonas com a-aminoaldeidos para a síntese estereosseletiva de 3-hidroxi-4-aminocetonas. Estas reações forneceram os adutos de aldol com estereoquímica relativa 1,2-syn, com estereosseletividades na faixa de 66:33 a >95:05 e rendimentos que variaram de 30-92% / Abstract: The chapter 1 describes the boron-mediated aldol reactions of a-methyl-b-alkoxy methylketones with achiral aldehydes. The results described here suggest a possible competition between 1,4 and 1,5 stereoindution in the construction of C-C bonds. These reactions gave the corresponding aldol adducts with selectivities ranging from 50:50 to 70:30 in good yields (82.95%). The Chapter 2 describes the aldol reaction of boron enolates generated from methylketones with chiral a-amino aldehydes for the stereoselective synthesis of 4-N-Boc-amino-3-hydroxy ketones. These reactions gave the 1,2.syn aldol aducts with diastereoselectivities ranging from 66:33 to 95:05 in good overallyields (30-92%) / Mestrado / Quimica Organica / Mestre em Química

Orientador: Luiz Carlos Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T11:30:26Z (GMT). No. of bitstreams: 1 Ferreira_MarcoAntonioBarbosa_M.pdf: 7153235 bytes, checksum: e612e11ed109a87cf51fbc6e47852412 (MD5) Previous issue date: 2008 / Resumo: ADIÇÃO DE ENOLATOS DE BORO DE METILCETONAS A ALDEÍDOS. A presenca de um b-heteroatomo em enolatos de boro de metilcetonas tem forte influência na estereoquímica das reações aldólicas correspondentes. As reações aldólicas mediadas por enolatos de boro de metilcetonas com P = PMB com aldeídos aquirais conduziram a altos níveis de estereoindução remota 1,5-anti. No caso das metilcetonas com P = TBS e P = t-Bu, a adição dos enolatos de boro correspondentes a aldeídos quirais conduziu a uma mistura dos diastereoisômeros favorecendo os adutos de aldol 1,5-syn. A natureza do substituinte nos anéis aromáticos não teve influência significativa na estereoquímica das reações aldólicas, levando a resultados similares. LIGAÇÕES DE HIDROGÊNIO INTRA E INTERMOLECULARES DE ÉTERES ALQUÍLICOS E DE SILÍCIO: ESTUDO TEÓRICO E EXPERIMENTAL. Investigou-se o impacto eletrônico do grupo protetor P (TBS ou PMB) no equilíbrio conformacional dos álcoois (R)-metil substituídos 139 (P = TBS) e 140 (P = PMB). A análise conformacional e experimentos de H NMR para os álcoois 139 e 140 refletiram a tendência para a existência de confôrmeros apresentando ligação de hidrogênio. Mostrou-se que a magnitude da ligação de hidrogênio de éteres alquílicos e de silício são dependentes de diversas propriedades, como interação de orbitais, hibridização e energia dos pares de elétrons não ligantes do oxigênio, e não apenas pela ocupância eletrônica do átomo aceptor / Abstract: ADDITION OF BORON ENOLATES OF METHYLKETONES TO ALDEHYDES. The presence of a b-heteroatom substituent in the boron enolates of methylketones has a strong influence in the stereochemical outcome of the corresponding aldol reactions. The boron-mediated aldol reactions of methylketones with P = PMB were found to proceed with high degrees of remote 1,5-anti stereoinduction. In the case of methylketones with P = TBS and P = t-Bu, the corresponding boron enolates additions to aldehydes gives a mixture of aldol adducts favoring the 1,5-syn adducts. The nature of the substituent at the aromatic ring does not influence the stereochemical outcome, as p-OMe and p-NO2 lead to similar results.INTRA AND INTERMOLECULAR HYDROGEN BONDS IN ALKYL AND SILYL ETHERS: EXPERIMENTAL AND THEORETICAL ANALYSIS. We have investigated the electronic impact of the P protecting group (TBS or PMB) in the conformational equilibrium of (R)-methyl substituted alcohols 139 (P = TBS) and 140 (P = PMB). The conformational analysis and H NMR experiments for alcohols 139 and 140 reflect the tendency for the existence of hydrogen-bonded conformations. We showed that the extents of the hydrogen bonds in silyl and alkyl ethers are determined by several properties, such as orbital interactions, lone pair hybridizations, and lone pair energies, and not just by the electronic occupancy of the acceptor atom / Mestrado / Quimica Organica / Mestre em Química