1,3-Diaza-2-azoniaallene Salts, Novel N3-Building Blocks: Preparation and Cycloadditions to Olefins
作者:Wolfgang Wirschun、Johannes C. Jochims
DOI:10.1055/s-1997-1161
日期:1997.2
Introduced are 1,3-diaza-2-azoniaallene salts R1 - N = N+ = N - R2 X- (6) representing a new functional group. The reactive intermediates 6 are prepared by reaction of N-chlorotriazenes R1 - N = N - NCl - R2 (8) with Lewis acids. The salt 6a is stable below -50°C. It shows a strong IR band at 2018 cm-1, equivalent aryl groups in the 1H and 13C NMR spectra, and gives a correct elemental analysis. The allenes 6 undergo [4Ï- + 2Ï] cycloadditions to both electron-rich and electron-deficient olefins affording 4,5-dihydro-1,2,3-triazolium salts 11 ("1,3-dipolar cycloadditions with inverse electron demand"). The cycloadditions proceed with complete conversation of the stereochemistry of the olefins. Cycloadducts 11w, 11ai of dibutyl maleate rearrange in solution into the respective more stable trans-isomers 11v, 11ah. The structure of 11m was determined by X-ray structural analysis.
介绍了一种新的功能团:1,3-二氮-2-氮杂烯盐 R1 - N = N+ = N - R2 X- (6)。反应中间体 6 通过 N-氯三氮烯 R1 - N = N - NCl - R2 (8) 与路易斯酸反应制备而成。盐 6a 在低于 -50°C 的温度下稳定。它在 2018 cm-1 处显示出强烈的红外带,且在 1H 和 13C 核磁共振光谱中具有等效的芳基取代基,并且元素分析结果准确。烯烃 6 进行 [4π- + 2π] 环加成反应,适用于电子富集和电子缺乏的烯烃,生成 4,5-二氢-1,2,3-三氮唑盐 11(“具有反向电子需求的 1,3-双极性环加成”)。环加成反应在完全保持烯烃立体化学的情况下进行。二丁基马来酯的环加成产物 11w 和 11ai 在溶液中重排为各自更稳定的反式异构体 11v 和 11ah。通过 X 射线结构分析确定了 11m 的结构。