Adição de nucleofilos a ions N-aciliminios quirais e reações de ciclização promovidas por Pd(0) / Nucleophilic addition to chiral N-acyliminium ions and palladium(0)-mediated cyclization reactions

AUTOR(ES)

Luis Gustavo Robello

DATA DE PUBLICAÇÃO

2006

RESUMO

The first part of this work described the addition of carbon nucleophiles to chiral N-acyliminium ions derived from tetrahydroisoquinoline. Once established for the racemic series, the methodology was explored with chiral N-acyliminium ions derived from (1R,2S)-(-)-trans-phenylcyclohexanol (97) and (1R,2S,5R)-(-)-8-phenylmenthol (98). The addition of allyltrimethylsilane (86b) to chiral N-acyliminium ions afforded the corresponding products 104b and 106b in moderate yields (65 and 56%) and low diastereoisomeric ratios (dr = 1,6:1 and 1,8:1 when 97 and 98 were used, respectively). The vinylogous Mannich addition of triisopropylsilyloxyfuran (86c) afforded the corresponding butenolides 104c and 106c in 42-52% yields. However, the diastereoisomeric ratios (dr = 3:1 and 2:1) were determined after the conversion of 104c e 106c to the hydroxy lactam 89 with recovery of chiral auxiliaries 97 and 98. Low diastereoselection (dr = 1,2:1 -1,4:1) was observed in the addition of allylbutylstannane (86d) to chiral N-acyliminium ions containing trans-a- and b-naphtylcycloexyl-based chiral auxiliaries, generated in situ from the reaction between chiral cloroformates (116b,c) and dihydroisoquinoline (111) or isoquinoline (118). In the second part of this work, palladium(0)-catalysed tandem cyclizations of alkynyl lactams were investigated. These alkynyl lactams were prepared in good yields from a new protocol involving the one pot generation of N-acyliminium ions followed by the addition of zinc alkynylides mediated by zinc triflate(II). After systematic studies aiming the optimization of the reaction conditions, the sequence intramolecular Heck - intermolecular Heck - 6p electrocyclization of 183a afforded the corresponding [5,5,6]-benzoindolizinine 213a. The success of this study offers a wide range of possibilities for the efficient construction of others aza-tricycles in a single process step.

ASSUNTO(S)

tandem reactions auxiliares quirais n-acyliminium ions catalise por paladio ions n-aciliminio chiral auxiliaries reações tandem palladium catalyzed

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