One-Pot Formation of Piperidine- and Pyrrolidine-Substituted Pyridinium Salts via Addition of 5-Alkylaminopenta-2,4-dienals to <i>N</i>-Acyliminium Ions: Application to the Synthesis of (±)-Nicotine and Analogs
triflate, followed by dehydrative cyclization, allowed the formation of pyridiniumsalts substituted at their 3-position by a five- or six-membered nitrogen heterocycle. Subsequent N-dealkylation of the pyridinium moiety and deprotection of the secondary amine or reduction of the carbamate function led to (±)-nicotine and analogs.
Oxazinone versus allene formation in the reaction of N-alkoxycarbonyliminium ions with propargyltrimethylsilane
作者:Peter M. Esch、Henk Hiemstra、W.Nico Speckamp
DOI:10.1016/s0040-4039(00)80098-2
日期:1988.1
Reactions of N-alkoxycarbonyliminium ions with propargyltrimethylsilane, promoted by Lewis acid, yield in most cases mixtures of allenes G and oxazinones H.
Intermolecular reacitons of N-alkoxycarbonyliminium ions with propargyltrimethylsilane; oxazinone versus allene formation
作者:Peter M. Esch、Henk Hiemstra、W. Nico Speckamp
DOI:10.1016/0040-4020(92)85018-a
日期:1992.1
Intermolecular reactions of N-alkoxycarbonyliminium ions with propargyltrimethylsilane mainly lead to 6-(trimethylsilyl)methyl-3,4-dihydro-2H-1,3-oxazinones, formed by intramolecular trapping of a stabilized β-silyl vinylic cation. α-Allenyl carbamates are obtained as minor products. The oxazinone/allene ratio is dependent on the nature of the Lewis acid and the solvent used.
The Lewis acid mediated reaction of carbamates with γ-oxygenated allyltin and its application to (±)-statine synthesis
作者:Yoshinori Yamamoto、Martin Schmid
DOI:10.1039/c39890001310
日期:——
The Lewisacidmediatedreaction of acyliminium ions (6) with γ-oxygen substituted allyltin (1c) gave the amino alcohol derivatives (7) and/or (8) in good yields; in certain cases very high diastereoselectivity was achieved and the procedure was applied to the synthesis of (±)-statine.
Microwave-assisted synthesis of α-ethoxycarbamates
作者:Alexandre Lumbroso、Floris Chevallier、Isabelle Beaudet、Jean-Paul Quintard、Thierry Besson、Erwan Le Grognec
DOI:10.1016/j.tet.2009.09.023
日期:2009.11
An efficient and reproducible synthesis of various alpha-ethoxycarbamates is described via a microwave heating mode. Compared to the thermal process. the microwave dielectric heating induces a dramatic reduction of the reaction time and the improvement of the yields. The reaction is general since applicable to aromatic and aliphatic aldehydes with various primary amines. Several examples involving chiral aldehydes have also been considered. (C) 2009 Elsevier Ltd. All rights reserved.