Tuning Stereoselection in Tethered Biginelli Condensations. Synthesis of cis- or trans-1-Oxo- and 1-Iminohexahydropyrrolo[1,2-c]pyrimidines.
Tuning Stereoselection in Tethered Biginelli Condensations. Synthesis of cis- or trans-1-Oxo- and 1-Iminohexahydropyrrolo[1,2-c]pyrimidines.
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调整系留 Biginelli 凝聚中的立体选择。
DOI：
10.1002/chin.199933173
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
L. Overman
中科院分区：
文献类型：
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作者：
A. McDonald;L. Overman
可以调整系留Biginelli缩合中的立体选择性以得到1-氧代六氢吡咯并[1，2-c]嘧啶和1-亚氨基六氢吡咯并[1，2-c]嘧啶产物的顺式或反式立体异构体（参见等式1）。对于具有脲和N-磺酰基胍官能团的底物（方案2和4），当在Knoevenagel条件下完成缩合时观察到顺式立体选择（4-7：1），而当在多磷酸酯（PPE）存在下进行缩合时观察到反式立体选择（4-20：1）。在这两种条件下，立体选择性是最高的N-磺酰基胍系列。对于带有碱性胍单元的底物，反式产物仅在Knoevenagel条件下形成（方案3）。
Stereoselection in tethered Biginelli condensations can be tuned to give either the cis or trans stereoisomer of 1-oxohexahydropyrrolo[1,2-c]pyrimidine and 1-iminohexahydropyrrolo[1,2-c]pyrimidine products (see eq 1). With substrates having urea and N-sulfonylguanidine functionality (Schemes 2 and 4), cis stereoselection (4-7:1) is observed when the condensation is accomplished under Knoevenagel conditions, while trans stereoselection (4-20:1) is observed when the condensation is carried out in the presence of polyphosphate ester (PPE). Under both conditions, steroselectivity is highest in the N-sulfonylguanidine series. With substrates bearing a basic guanidine unit, the trans product is formed exclusively under Knoevenagel conditions (Scheme 3).