RESUMEN
A short and efficient synthesis of 4-aminomethyl-4-fluoropiperidines and 3-aminomethyl-3-fluoropyrrolidines is described. These fluorinated azaheterocycles are of specific interest as bifunctional building blocks for fluorinated pharmaceutical compounds. The key step of the synthetic pathway involves the regioselective bromofluorination of N-Boc-4-methylenepiperidine and 3-methylenepyrrolidine using Et(3)N.3HF and NBS.
Asunto(s)
Flúor/química , Piperidinas/síntesis química , Pirrolidinas/síntesis química , Química Farmacéutica , Estructura Molecular , Piperidinas/química , Pirrolidinas/química , EstereoisomerismoRESUMEN
Synthetic strategies toward 3-fluoroazetidine-3-carboxylic acid, a new cyclic fluorinated beta-amino acid with high potential as building block in medicinal chemistry, were evaluated. The successful pathway includes the bromofluorination of N-(diphenylmethylidene)-2-(4-methoxyphenoxymethyl)-2-propenylamine, yielding 1-diphenylmethyl-3-hydroxymethyl-3-fluoroazetidine after reduction of the imino bond, ring closure, and removal of the 4-methoxybenzyl group. Changing the N-protecting group to a Boc-group allows further oxidation to 1-Boc-3-fluoroazetidine-3-carboxylic acid, a new fluorinated heterocyclic amino acid.
Asunto(s)
Aminoácidos/síntesis química , Azetinas/síntesis química , Ácidos Carboxílicos/síntesis química , Compuestos Heterocíclicos/síntesis química , Aminoácidos/química , Azetinas/química , Ácidos Carboxílicos/química , Compuestos Heterocíclicos/química , Estructura Molecular , EstereoisomerismoRESUMEN
Difluoropiperidines attract considerable interest from organic and medicinal chemists, but their synthesis is often problematic. This paper describes a new synthetic pathway toward valuable 3,3-difluoropiperidines starting from suitable delta-chloro-alpha,alpha-difluoroimines. The latter imines can be synthesized via electrophilic fluorination of the corresponding delta-chloroimines using NFSI (N-fluorodibenzenesulfonimide) in acetonitrile. After hydride reduction of the imino bond and subsequent intramolecular substitution of the chloride atom, new 3,3-difluoropiperidines were obtained in good yields. In addition, this methodology was applied to establish the first synthesis of N-protected 3,3-difluoropipecolic acid, a new fluorinated amino acid.
Asunto(s)
Compuestos de Flúor/síntesis química , Piperidinas/síntesis química , Compuestos de Flúor/química , Estructura Molecular , Piperidinas/químicaRESUMEN
A new route for the synthesis of stable 3-alkyl- and 3-aryl-2(,2)-(di)fluoroaziridines was developed by hydride reduction of novel alpha-bromo- and alpha-chloro-alpha(,alpha)-(di)fluoroketimines and subsequent ring closure of beta-fluorinated beta-chloro- and beta-bromoamines. This is the first report on the synthesis of 2,2-difluoroaziridines sensu stricto.
Asunto(s)
Aziridinas/síntesis química , Flúor/química , Aziridinas/química , CiclizaciónRESUMEN
[reaction: see text] A mild and efficient procedure to synthesize alpha-fluoro- and alpha,alpha-difluoroimines was developed. Various N-alkylimines derived from acetophenones were successfully monofluorinated using NFSI (N-fluorobenzenesulfonimide) in a mixture of CH(3)CN and DMF at 0 degrees C. Alternatively, the same procedure without DMF gave rise to difluorinated imines when performed at room temperature. The obtained alpha- and alpha,alpha-difluorinated imines were subsequently reduced to give the corresponding beta-fluoro- and beta,beta-difluoroamines in good yield.
RESUMEN
A straightforward synthesis toward 2-fluorinated aziridines was developed via ring closure of beta-fluorinated beta-chloroamines, which were obtained via reduction of the corresponding alpha-fluorinated amides by borane. When 1-benzyl-2-fluoroaziridine was treated with methanol, reaction occurred at the 2-position, giving rise to N-benzyl-2,2-dimethoxyethylamine, while in the case of 1-benzyl-2,2-difluoroaziridine the 3-position was attacked, giving rise to N-benzyl-2-methoxyacetamide. These reactions point to the divergent reactive behavior of monofluoro- and difluoroaziridines.