“Tandem” reactivity of 2-cyano-Δ3-piperideines: a new approach to the synthesis of ervatamine type indole alkaloids.
作者:Jean-Luc Bettiol、Ildiko Buck、Henri-Phillippe Husson、David S. Grierson、Anna Diez、Mario Rubiralta
DOI:10.1016/s0040-4039(00)92400-6
日期:1991.9
Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, 08028-Barcelona, Spain. The synthesis of 20-dethylsilicine in four steps, from a 2-cyano-Δ3-piperideine substituted at C-3 by a CH2OAc group, is reported.
Synthesis of 20-deethylsilicine from a second-generation 2-cyano-.DELTA.3-piperidine synthon
作者:David S. Grierson、Jean Luc Bettiol、Ildiko Buck、Henri Philippe Husson、Mario Rubiralta、Anna Diez
DOI:10.1021/jo00050a012
日期:1992.11
The Zn2+ ion mediated reaction of the 2-cyano-DELTA3-piperidine 9a (X = SO2C6H5) with the silyl enol ether of Na-methyl-2-acetylindole (24) led to formation of compounds 29a,b (70%) resulting from introduction of the acetylindole moiety at the exocyclic (C-7) carbon center and migration of the phenylsulfonyl group from C-7 to C-4. In contrast, reaction of 2-Cyano-DELTA3-piperidine 9b (X = CN) with 24 gave the desired C-4 acetylindole-substituted products 36a,b (1:1.3 mixture; 72% overall yield). Attempts to cyclize intermediates 36 to the tetracyclic enamine 27 were unsuccessful. Alternatively, the Zn2+-catalyzed reaction of synthons 9a and 9b with indole gave the C-7 indole-substituted aminonitriles 37a,b and 38, respectively. These intermediates were converted to DELTA2-piperidine 40 on reaction with sodium dimethyl malonate and AgBF4. Stereoselective hydrogenation of the enamine double bond in 40 furnished the required cis 3,4-disubstituted piperidine 41, which was cyclized under acidic conditions to the target molecule, 20-deethylsilicine (20).