金剛烷衍生物與苯□氧化物行 1,3-偶極環化加成反應之面向選擇性研究

Abstract

苯□氧化物 (benzonitrile oxide, 4-H) 與碳-5取代金剛硫酮 (7-X)、亞甲基金剛烷 (8-X) 與金剛亞胺 (9-X) 進行1,3-偶極環化加成反應，可分別產生具二種異構化之 D2-1,4,2-oxadiazolines、D2-isoxazolines 及 D2-1,2,4-oxadiazolines產物。除了金剛亞胺系列於不同溫度及不同反應時間下，其異構化產物比例均約為1：1之外；其餘二種金剛烷系列之反應，其反應試劑皆偏好從反應中心zu方位進行加成 (產物比例約為60：40)，這些趨勢可以反應過渡態超共軛理論與前緣分子軌域理論計算結果加以解釋。 苯環對位取代基之苯□氧化物 (拉電子基：F、Cl、Br、CN、NO2；推電子基：CH3、OMe) 分別與 7-F及 8-F進行反應的研究當中，從線性 Hammett 圖所得之 Dr 差值，分別為 + 0.12 及 0.0。從這些甚小的值與先前的研究可顯示出 1,3-偶極環化加成反應為〝concerted〞機構，且反應過渡態具些微電荷分佈的差異；另從溫度效應研究當中，首次觀察到syn 及anti型式反應過渡態間活化參數之差異，從中亦可說明面向選擇性研究結果之現象。 另外，於合成碳5取代金剛硫酮時，發現用不同當量數之 P4S10可產生具 trithiolane 結構之雙金剛烷化合物，其結構由 X-ray 單晶繞射結構圖確定。而此化合物於MCPBA氧化後之產物結構，也可由碳核磁共振光譜及質譜加以鑑定。

The 1,3-dipolar cycloaddition reactions of benzonitrile oxide (4-H) with 5-substituted adamantane-2-thiones (7-X), -methyleneadamantane (8-X) and -N-benzyladamantyl-2-imines (9-X) produced two geometrically isomeric D2-1,4,2-oxathiazolines, D2-isoxazolines and D2-1,2,4-oxadiazolines, respectively. The substituents varied from fluoro, chloro, bromo to phenyl. The face selectivity in the latter reaction was found to be ~ 1:1 regardless of the variations in 5-substituent, reaction time and temperature. For the former two reactions, the product formation bias resulting from the favored attack of nitrile oxide on the zu-face is discussed in terms of transition-state hyperconjugation and frontier molecular orbital theory. In the study of the reactions of p-substituted benzonitrile oxides (4-X) with 7-F and 8-F, the p-substituent was varied from electron-withdrawing (F, Cl, Br, CN or NO2) to -releasing (Me, OMe). The face selectivity was measured in all cases. The differences Dr for the reactions of 7- and 8-F with 4-X were obtained from linear Hammett plots; they are +0.12 and 0.0, respectively. These low values and information from previous studies imply a concerted-one-step mechanism with very little charge distribution differences in the transition states. These effects of temperature on the Z/E product ratios provide us, for the first time, with activation parameter differences between the syn- and anti transition states; there values are discussed. In the synthesis of 5-substituted adamantane-2-thiones, we found that a novel diadamantane compound with trithiolane structure was produced by various amount of P4S10. The structure was confirmed by X-ray single-crystal analysis. The products of oxidation reaction of the trithiolane compound with MCPBA were determined by 13C-NMR and mass spectra.