Double transacetalization of diacylium ions.
Double transacetalization of diacylium ions.
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二酰基离子的双转缩醛化。
DOI：
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发表时间：
2000
影响因子：
2.3
通讯作者：
M. Eberlin
中科院分区：
文献类型：
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作者：
R. Sparrapan;M. Mendes;M. Eberlin
报道了O=C=X(+)=C=O型（X = N， CH）二烷基离子与环缩醛或环缩醛的双交换缩醛反应。该反应是放热的，效率很高，并形成了一类新的高电荷离域离子：环离子双酮。五极双级和三级质谱(MS（2)和MS(3)）实验表明，O=C=N(+)=C=O和O=C=CH(+)=C=O具有较高的双交换缩醛反应活性，而在MS(3)实验中，O=C=N(+)=C=O和O=C=CH(+)=C=O与不同缩醛依次进行单和双交换缩醛反应合成不同取代的环离子双酮。对于环缩醛，acyium - thiioacyium离子O=C=N(+)=C=S在acyium位上通过单转乙酰化反应迅速而选择性地发生反应，而其环离子缩醛的游离thiacyium位通过双转乙酰化反应几乎不发生反应。因此，只有O=C=N(+)=C=S的acyum位点能被交换缩醛有效保护。低能MS(3)碰撞诱导的O=C=N(+)=C=O和O=C=CH(+)=C=O的环离子双酮的解离，依次释放每个受保护的酰基位，形成单衍生化离子，然后形成完全去保护的二酰基离子。
A novel gas-phase reaction of diacylium ions of the O=C=X(+)=C=O type (X = N, CH) is reported: double transacetalization with cyclic acetals or ketals. The reaction is exothermic and highly efficient, and forms members of a new class of highly charged-delocalized ions: cyclic ionic diketals. Pentaquadrupole double- and triple-stage mass spectrometric (MS(2) and MS(3)) experiments reveal the high double transacetalization reactivity of O=C=N(+)=C=O and O=C=CH(+)=C=O, whereas the synthesis of differently substituted cyclic ionic diketals is performed in MS(3) experiments via sequential mono- and double transacetalization of O=C=N(+)=C=O and O=C=CH(+)=C=O with different acetals. With cyclic acetals, the acylium-thioacylium ion O=C=N(+)=C=S reacts promptly and selectively by mono-transacetalization at its acylium site, but the free thiacylium site of its cyclic ionic ketal is nearly unreactive by double transacetalization. Therefore, only the acylium site of O=C=N(+)=C=S can be efficiently protected by transacetalization. Low-energy MS(3) collision-induced dissociation of the cyclic ionic diketals of O=C=N(+)=C=O and O=C=CH(+)=C=O sequentially frees each of the protected acylium site to form the mono-derivatized ion, and then the fully deprotected diacylium ion.