Adição de nucleofilos de carbono a ions N-aciliminio substituidos

AUTOR(ES)

Adriano Otavio Maldaner

DATA DE PUBLICAÇÃO

1999

RESUMO

This work describes the studies on the addition of carbon nucleophiles to substituted N-acyliminium ions and the application of this methodology toward the stereoselective synthesis of piperidine, quinolizidine, indolizide and decahydroquinoline systems. To achieve this goal a-substituted N-Boc-2-piperidinones 2.18 and 2.19 and the N-Boc-2- pyrrolidinones 2.20 and 2.21 were obtained from glurarimide and succinimide after Grignard reactions, reduction of hydroxylactams and nitrogen protection with the tert-butiyl carbamate. These lactams were used as starting material in a systematic alkylation study, leading to 3,6-disubstituted N-Boc-2-piperidinones 2.22-2.24 and 2.28 and to 3,5-disubstituted N-Boc-2- pyrrolidinones 2.34, 2.35, 2.38-2.43 in 45-83% yield. trans-Disubstituted products were obtained in high diastereoselection (>94/6) after reaction of the corresponding lithium enolates with methyl iodide, allyl bromide and benzyl bromide. Carbonyl reduction followed by Lewis acid promoted in situ formation of the N-acyliminium ion paved the way for its reaction with several nucleophiles. The additjon of allyltributylstananne and silylenolethers to 6-membered N-acyliminium ions afforded 2,6-cis/2,3-trans trisubstituted piperidine derivatives in good yields (70-91%) and selectivities (de>80%). On the other hand, the addition of allyltributylstananne to 5-membered N-acyliminium ions led to the trisubstituted pyrrolidine derivatives with low distereoisomeric ratio (1.1/1-2.2/1). The methodology developed for the stereoselective preparation of trissubstituted piperidine derivatives was employed in the preparation of the racemic form of decahydroquinoline 4.3, indolizidine 4.4, 2,4-bis-epi-plumerinine 4.16 and Indolizjdine 209B.

ASSUNTO(S)

lactamas quimica organica

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