Síntese de ligantes cobaltoceno-imidazolina e cobaltoceno-oxazolina para aplicação em reações de carboboração e hidrocarbofuncionalização enantiosseletivas
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Data
2024-05-02
Autores
Pereira, Brenda Regina Bondezan [UNIFESP]
Orientadores
Rodrigues, Alessandro [UNIFESP]
Tipo
Dissertação de mestrado
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Resumo
A catálise assimétrica se tornou um método relevante para o controle estereoquímico na obtenção de produtos. O presente trabalho consistiu em dois objetivos: 1) a síntese e caracterização de 2 ligantes inéditos do tipo imidazolina-cobaltoceno (N-Ts e N-Boc) e 1 ligante inédito do tipo cobaltoceno-oxazolina e 2) avaliação destes ligantes em reações estereosseletivas de 1,2-carboboração e hidrocarbofuncionalização de alcenos não ativados. A síntese dos ligantes N-Ts (I-A) e N-Boc (I-B) se deu em 5 etapas, partindo do ciclopentadieno de sódio na presença de dimetilcarbonato e clorotris(trifenilfosfina)cobalto(I), obtendo 399 com rendimento de 73%, reduzido para 400 na presença de DIBAL-H, com rendimento de 79%. Em seguida, este foi oxidado com IBX, fornecendo rendimento de 63%. 402 foi obtido rendimento de 86% por ciclização com (1S,2S)-1,2-difenil-1,2-etilenodiamina, seguida pela oxidação com iodo e carbonato de potássio e, posteriormente, tosilado na presença de cloreto de tosila e trietilamina, obtendo-se o ligante I-A com rendimento de 32%. Para o ligante I-B foi empregado dicarbonato de di-terc-butila ao 402, obtendo um rendimento de 48%. Para a síntese do ligante II-A, houve a clivagem de 399 na presença de terc-butóxido de potássio, obtendo o ácido carboxílico com rendimento de 61%. Na sequência, o ácido carboxílico 400 foi convertido para cloreto de ácido, que foi usado na síntese da amida na presença de trietilamina e (S)-2-amino-2-feniletanol. A etapa posterior consistiu na ciclização do anel oxazolínico na presença de trietilamina e cloreto de tosila, obtendo 81% de rendimento. I-A foi obtido com rendimento de 8 % e II-A 19 %. I-B foi obtido com rendimento de 26 %. Os ligantes foram caracterizados por RMN de 1H, RMN de 13C, EMAR, atividade óptica e IV. I-A e II-A foram testados em reações de 1,2-carboboração e hidrocarbofuncionalização de alcenos não ativados. No entanto, em nenhum dos testes realizados houve formação de produto.
Asymmetric catalysis has become a relevant method for stereochemical control in obtaining products. The present work consisted of two objectives: 1) the synthesis and characterization of two new ligands of the imidazoline-cobaltocene type (N-Ts and N-Boc) and one new ligand of the cobaltocene-oxazoline type and 2) evaluation of these ligands in stereoselective reactions of 1,2-carboboration and hydrocarbofunctionalization of non-activated alkenes. The synthesis of the ligands N-Ts (I-A) and N-Boc (I-B) took place in 5 steps, starting from sodium cyclopentadiene in the presence of dimethylcarbonate and chlorotris(triphenylphosphine)cobalt(I), obtaining 399 with 73% yield, reduced to 400 in the presence of DIBAL-H, with a yield of 79%. The compound 400 was then oxidized with IBX, providing 63% yield of 402, a yield of 86% was obtained by cyclization with (1S,2S)-1,2-diphenyl-1,2-ethylenediamine, followed by oxidation with iodine and potassium carbonate and, subsequently, tosylated in the presence of tosyl chloride and triethylamine, obtaining the I-A ligand in 32% yield. For the I-B ligand, di-tert-butyl dicarbonate 402 was used, obtaining 48% yield. For the synthesis of the II-A ligand, 399 was cleaved in the presence of potassium tert-butoxide, obtaining the carboxylic acid 61% yield. The carboxilic acid was converted to acid chloride, used directly in the next step, which consisted of the synthesis of the amide in the presence of triethylamine and (S)-2-amino-2-phenylethanol. The subsequent step consisted of cyclization of the oxazoline ring in the presence of triethylamine and tosyl chloride, obtaining 81% yield. I-A was obtained with a yield of 8% and II-A 19 %. I-B was obtained in 26% yield. The ligands were characterized by 1H NMR, 13C NMR, EMAR, optical activity and IR. I-A and II-A were tested in 1,2-carboboration and hydrocarbofunctionalization reactions of non-activated alkenes. However, none of the tests carried out resulted in product formation.
Asymmetric catalysis has become a relevant method for stereochemical control in obtaining products. The present work consisted of two objectives: 1) the synthesis and characterization of two new ligands of the imidazoline-cobaltocene type (N-Ts and N-Boc) and one new ligand of the cobaltocene-oxazoline type and 2) evaluation of these ligands in stereoselective reactions of 1,2-carboboration and hydrocarbofunctionalization of non-activated alkenes. The synthesis of the ligands N-Ts (I-A) and N-Boc (I-B) took place in 5 steps, starting from sodium cyclopentadiene in the presence of dimethylcarbonate and chlorotris(triphenylphosphine)cobalt(I), obtaining 399 with 73% yield, reduced to 400 in the presence of DIBAL-H, with a yield of 79%. The compound 400 was then oxidized with IBX, providing 63% yield of 402, a yield of 86% was obtained by cyclization with (1S,2S)-1,2-diphenyl-1,2-ethylenediamine, followed by oxidation with iodine and potassium carbonate and, subsequently, tosylated in the presence of tosyl chloride and triethylamine, obtaining the I-A ligand in 32% yield. For the I-B ligand, di-tert-butyl dicarbonate 402 was used, obtaining 48% yield. For the synthesis of the II-A ligand, 399 was cleaved in the presence of potassium tert-butoxide, obtaining the carboxylic acid 61% yield. The carboxilic acid was converted to acid chloride, used directly in the next step, which consisted of the synthesis of the amide in the presence of triethylamine and (S)-2-amino-2-phenylethanol. The subsequent step consisted of cyclization of the oxazoline ring in the presence of triethylamine and tosyl chloride, obtaining 81% yield. I-A was obtained with a yield of 8% and II-A 19 %. I-B was obtained in 26% yield. The ligands were characterized by 1H NMR, 13C NMR, EMAR, optical activity and IR. I-A and II-A were tested in 1,2-carboboration and hydrocarbofunctionalization reactions of non-activated alkenes. However, none of the tests carried out resulted in product formation.
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Citação
PEREIRA, Brenda Regina Bondezan. Síntese de ligantes cobaltoceno-imidazolina e cobaltoceno-oxazolina para aplicação em reações de carboboração e hidrocarbofuncionalização enantiosseletivas.2024.175 f. Dissertação (Mestrado em Química-Ciência e Tecnologia da Sustentabilidade) - Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema, 2024.