Alkali metal cations control over nucleophilic substitutions on aromatic fused pyrimidine-2,4-[1H,3H]-diones: towards new PNA monomers
Alkali metal cations control over nucleophilic substitutions on aromatic fused pyrimidine-2,4-[1H,3H]-diones: towards new PNA monomers
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碱金属阳离子控制芳香族稠合嘧啶-2,4-[1H,3H]-二酮上的亲核取代：朝向新的 PNA 单体
DOI：
10.1016/j.tet.2012.08.028
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发表时间：
2012-10-28
期刊：
影响因子：
2.1
通讯作者：
Yao, Jiannian
中科院分区：
文献类型：
--
作者：
Li, Pengfa;Zhan, Chuanlang;Yao, Jiannian
本文报道了一系列芳香稠合嘧啶-2，4（3 H）-二酮-1-基乙酸的合成以及含这些多环核碱基类似物的新PNA单体的合成。在嘧啶-2，4-[1H，3 H]-二酮的5，6-位上引入稠合芳环会产生空间位阻效应和电荷离域效应，削弱了1-位和3-位上的亲核取代。我们发现碱金属阳离子在烷基化反应中起着重要的作用。LiOH比NaOH更有效地进行烷基化反应，而KOH几乎不起作用。碱金属阳离子的这种影响可能是由于嘧啶-2，4-二氧化物阴离子和碱金属阳离子之间的电荷配对相互作用重新排列了整个芳香体系周围的电荷分布，增加了1-和3-氮原子上的负电荷分布，从而增强了这些位置上的亲核反应性。(C)2012爱思唯尔有限公司保留所有权利。
In this paper we report synthesis of a series of aromatic fused pyrimidine-2,4(3H)-dione-1-yl acetic acid and new PNA monomers containing these polycyclic nucleobase analogues. Introduction of a fused aromatic ring onto the 5,6-positions of the pyrimidine-2,4-[1H,3H]-diones brings about the steric effects and the charge delocalization, both weakening the nucleophilic substitutions on the 1- and 3-positions. We found that alkali metal cations play an important role in this alkylation reaction. LiOH brings out a much more efficient alkylation than NaOH does, while KOH nearly does not work on this reaction. Such influences from the alkali metal cations are probably due to that the charge-pairing interactions between the pyrimidine-2,4-dioxide anions and the alkali metal cations rearrange the charge distribution around the whole aromatic system and increase the negative charge distribution on the 1- and 3-nitrogen atoms, which then strengthens the nucleophilic reactivity on these positions. (C) 2012 Elsevier Ltd. All rights reserved.