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1.
J Org Chem ; 88(14): 9686-9703, 2023 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-37437127

RESUMO

The In(OTf)3-catalyzed α-vinylation of various hydroxy-functionalized quaternary carbon centers using in situ generated isobutylene from tert-butyl acetate is presented as a novel synthetic methodology. Moreover, tert-butyl acetate is a nonflammable feed stock and is a readily available source for the in situ production of vinyl substituents, as demonstrated by the vinylation reaction with quaternary hydroxy/methoxy compounds. Moreover, an excellent selectivity for methylallylation over vinylation was obtained with Ni(OTf)2 as a catalyst. In the case of peroxyoxindole, methylallyl-functionalized 1,4-benzoxazin-3-one derivatives were formed through the sequential rearrangement of peroxyoxindole followed by the nucleophilic attack by isobutylene. The detailed mechanism for this reaction and rationalization for the selectivity are provided using kinetics and density functional theory studies.

2.
J Org Chem ; 86(13): 8805-8828, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-34151556

RESUMO

A base-free and acceptorless Ru-catalyzed dehydrogenative approach has been developed for the synthesis of N-heterocycles by using 1,3-dicarbonyls and amino alcohols through a domino sequential enamine formation and intramolecular oxidative cyclization strategy. This unified approach is also applicable for the synthesis of O-heterocycles involving 2-hydroxybenzyl alcohol as a coupling reactant via consecutive C-alkylation and intramolecular cyclization steps. The present protocol is general for the synthesis of varieties of biologically important scaffolds, such as tetrahydro-4H-indol-4-one, 3,4-dihydroacridin-1(2H)-one, and tetrahydro-1H-xanthen-1-ones derivatives using a single catalytic system, viz. RuH2CO(PPh3)3. Environmentally benign H2O and H2 are the only byproducts in this domino process. Moreover, RuH2CO(PPh3)3-catalyzed C3-alkylation of tetrahydro-4H-indol-4-one using alcohol as a alkylating partner is also described in this report. For the first time, a solvent-free gram-scale reaction for the acceptorless dehydrogenative annulation has been demonstrated. A plausible mechanism for the Ru-catalyzed base-free and acceptorless dehydrogenative annulation of amino alcohols or 2-hydroxybenzyl alcohols has been provided with several experimental investigations and spectroscopic evidence.


Assuntos
Amino Álcoois , Alquilação , Catálise , Ciclização
3.
Org Lett ; 22(9): 3402-3406, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32310663

RESUMO

We report for the first time a continuous-flow strategy to execute O-sulfation modification of heparan sulfate (HS) oligosaccharides. A systematic investigation of the influence of the flow parameters on the installation of the sulfate group on glucosamine monosaccharide can aid the development of a comprehensive, quick, and reliable strategy for O-sulfation of HS oligosaccharide precursors. Deprotection of the sulfated heparin intermediates led to the development of a comprehensive biologically inspired oligosaccharide library to understand the crucial structure-function relationship of HS.


Assuntos
Heparitina Sulfato/química , Oligossacarídeos/química , Técnicas de Química Sintética/métodos , Etilaminas/química , Heparitina Sulfato/síntese química , Relação Estrutura-Atividade , Óxidos de Enxofre/química
4.
Org Biomol Chem ; 17(12): 3258-3266, 2019 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-30847455

RESUMO

An additive/Brønsted acid/base free, highly efficient and chemoselective transetherification of electron deficient vinylogous esters and water mediated de-alkylation using an earth-abundant Fe-catalyst under very mild reaction conditions is described. This reaction is highly selective to primary alcohols over secondary alcohols, has good functional group tolerance, is scalable to gram scale and a purification free sequential transetherification in a continuous flow mode is demonstrated.

5.
Org Biomol Chem ; 16(35): 6405-6409, 2018 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-30178810

RESUMO

A catalytic site selective intramolecular C-S bond forming reaction is demonstrated for the first time. The C-H bond functionalization of α-aryl-thioacetanilides was efficiently catalyzed by 2 mol% NiBr2, resulting in valuable 2-aminobenzo[b]thiophenes in moderate to good yields. Furthermore, the selective sp2 C-H bond functionalization over sp3 is exemplified.

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