Regioselective introduction of homoallylic amine moiety to quinolines: Preparation of reissert compound followed by in-mediated allylation of nitrile

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Title
Regioselective introduction of homoallylic amine moiety to quinolines: Preparation of reissert compound followed by in-mediated allylation of nitrile
Author(s)
S H Kim; Sangku Lee; Y M Kim; J N Kim
Bibliographic Citation
Bulletin of Korean Chemical Society, vol. 31, no. 12, pp. 3822-3825
Publication Year
2010
Abstract
Homoallylic amines are valuable building blocks in organic synthesis as precursors for β-amino acids and many hetero-cycles. 1-3 In addition, the structural motif is present in numerous biologically important substances. 3 During our recent studies on the reaction of allylindium rea-gents and nitrile moiety-containing substrates 4 we found that the imine intermediate, generated in situ by the reaction of a nitrile and allylindium reagents, could be quenched by a suitable electrophilic quencher in the same molecule to form a cyclic compound. 4 Inter-and intramolecular quenching of the imine intermediate has been known in limited cases. 5 Based on the previous results 4,5 we reasoned out that a regio-selective introduction of a homoallylic amine moiety at the 2-po-sition of quinoline could be accomplished by a simple two-step procedure, as shown in Scheme 1. The first step is a synthesis of Reissert compound of quinoline 6 and the next is an In-mediated allylation of nitrile moiety of the Reissert compound. 4,7 In the intermediate stage, an intramolecular transfer of benzoyl group would be possible because the dihydroquinoline residue is a good leaving group and the N-benzoylimine intermediate could be converted into the homoallylic amine by a consecutive 1,3-H shift (see, path-a in Scheme 2). In order to examine the feasibility of our assumption, a re-presentative Reissert compound 2a was prepared according to the reported method. 6f The reaction of 2a and allyl bromide was carried out in THF in the presence of indium metal at reflux-ing temperature for 20 min. To our delight, desired compound 3a was obtained in good yield (70%) along with a trace amount of imidazo[1,5-a]quinoline 4a (6%). 8 The reaction mechanism can be postulated as shown in Scheme 2. The reaction of 2a and allylindium reagents produced an imine intermediate (I), which produced N-benzoylimine intermediate (II) by following the path-a. The dihydroquinoline moiety acts as a leaving group to form (II). Successive 1,3-H transfers of (II) produced a homo-allylamine derivative 3a. Compound 4a was formed in a trace amount via the dehydrative cyclization (path-b).
Keyword
AllylationHomoallylic amineIndiumQuinolinesReissert compounds
ISSN
0253-2964
Publisher
Wiley
DOI
http://dx.doi.org/10.5012/bkcs.2010.31.12.3822
Type
Article
Appears in Collections:
Ochang Branch Institute > Anticancer Agent Research Center > 1. Journal Articles
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