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Design of Environmentally Benign Lewis Acid Catalysts Derived from Main Group Elements as an Active Center

以主族元素为活性中心的环保路易斯酸催化剂的设计

基本信息

批准号：
14340227
负责人：
TERADA Masahiro
金额：
$ 9.66万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340227/
关键词：
Main Group Elements Catalyst Environmentally Benign Lewis Acids Phosphrous Hypervalent Bond Molecular Design 硫黄

项目摘要

Lewis acid catalysts are utilized to valuable organic transformations. Although a number of approaches to develop metallic-Lewis acid catalysts were performed, little attention has been paid to explore main group elements as Lewis acidic center. A trityl cation is only the precedent example, in which stabilized carbonium cation function as an active center. The Lewis acids catalyst composed of main group elements can be constructed the catalyst molecule from covalent bonding leading to an advantage in catalyst recycling. Herein we wish to report phosphonium salts as novel Lewis acid catalysts wherein phosphonium salts interact with substrate via hypervalence bonding. Several phosphonium salts with mono or bicyclic ring structure were synthesized. We also introduce oxygen functionality as an electron-withdrawing group to stabilize hypervalence bonding. Phosphonium salts were prepared from the corresponding hydroxy phosphinate and trifluoromethanesulfonic anhydride in the presence of molecular sieves (MS) 4A at room temperature for 1 h. We attempted Lewis acid catalysis by phosphonium salts in Diels-Alder reaction. α,β-unsaturated amide was employed as a dienophile, because NMR experiment strongly suggested that the phosphonium salts function as an activator for amide functionality. In fact, remarkable rate acceleration was observed by using phosphonium salts. Diels-Alder products were obtained quantitatively within 2 h at 0℃. In summary, we performed novel Lewis acid catalysis by phosphonium salts in which dioxaphosphacycle is the key structure to function as Lewis acid catalysts through hypervalence bonding.

路易斯酸催化剂用于有价值的有机转化。金属-路易斯酸催化剂的开发方法有很多，但对主族元素作为路易斯酸中心的研究较少。三烷基阳离子只是一个先例的例子，其中稳定的碳离子作为活性中心起作用。由主族元素组成的路易斯酸催化剂可以由共价键构成催化剂分子，从而在催化剂回收方面具有优势。在此，我们希望报道磷酸盐作为新型路易斯酸催化剂，其中磷酸盐通过高价键与底物相互作用。合成了几种单环或双环结构的磷盐。我们还引入了氧官能团作为一个吸电子基团来稳定高价键。在分子筛（MS） 4A存在下，以相应的羟基膦酸盐和三氟甲烷磺酸酐为原料，在室温下反应1 h，制备了磷酸盐。采用α，β-不饱和酰胺作为二烯亲和剂，因为核磁共振实验强烈表明磷盐作为酰胺功能的激活剂。事实上，使用磷盐可以观察到显著的速率加速。Diels-Alder产物在0℃下2 h内定量得到。综上所述，我们利用磷盐进行了新的Lewis酸催化，其中二磷环是通过高价键作用作为Lewis酸催化剂的关键结构。