Stereoselective reduction and reductive dephosphonylation of β-iminophosphonates
作者:Mohamed Amedjkouh、Jacques Grimaldi
DOI:10.1016/s0040-4039(02)00521-x
日期:2002.5
Proline-like 2,4-dialkyl-5-phosphonylpyrrolidines 2 were obtained stereoselectively by reduction of the corresponding beta-iminophosphonates 1 with NaBH4. The detailed characterization of compounds 2 was accomplished by H-1 and C-13 NMR as well as by crystal structure analysis. When 1 was reduced with LiAlH4 the reaction gave dephosphonylated pyrrolidines 3. The latter method is suitable for providing substituted pyrrolidines regioselectively. A possible mechanism for the dephosphonylation is proposed. (C) 2002 Elsevier Science Ltd. All rights reserved.
3H-Pyrroles, Alkylidene-Pyrrolines and Functionalized Pyrrolidines by Radical Cyclization of β-Allenyliminyl Radicals
reaction of allene-tethered dithiosemicarbazides 4 is a convenient method for the preparation of five-membered unsaturated nitrogen heterocycles. The sulfur-directed intermolecular attack of the tin radical at the semicarbazide moiety leads to an allene-tethered iminyl radical, which then undergoes a 5-exo-dig cyclization leading to both the 3H-pyrroles 5 and the alkylidene pyrrolines 6; thermal isomerization