Enantioselective Diels-Alder reaction of α-acyloxyacroleins catalyzed by chiral 1,1′-binaphthyl-2,2′-diammonium salts
Enantioselective Diels-Alder reaction of α-acyloxyacroleins catalyzed by chiral 1,1′-binaphthyl-2,2′-diammonium salts
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DOI：
10.1002/adsc.200600322
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发表时间：
2006-11-01
影响因子：
5.4
通讯作者：
Ishihara, Kazuaki
中科院分区：
文献类型：
--
作者：
Sakakura, Akira;Suzuki, Kenji;Ishihara, Kazuaki
手性1，1 ′-联萘-2，2 ′-二胺（2a）和三氟甲磺酰亚胺（Tf 2NH）的二铵盐对α-酰基氧丙烯醛的Diels-Alder反应显示出优异的催化活性和对映选择性。例如，在5摩尔%的2a和9.5摩尔%的Tf 2NH的存在下，α-Alder反应在-75 ° C下，在EtCN中进行α-（环己烷羰基氧基）丙烯醛与环戊二烯的加成反应，以88%的产率得到具有92%exo和91%ee的加合物。酰氧基丙烯醛增加了对映选择性，这是由于酰基与过渡态的铵基质子形成了强的分子内氢键。该催化剂可以通过将市售手性二胺和Tf 2NH混合而容易地原位制备。
A diammonium salt of chiral 1,1'-binaphthyl-2,2'-diamine (2a) and trifluoromethanesulfonimide (Tf2NH) shows excellent catalytic activity and enantioselectivity for the Diels-Alder reaction of alpha-acyl-oxyacroleins. For example, in the presence of 5 mol % of 2a and 9.5 mol % of Tf2NH, the Diels-Alder reaction of alpha-(cyclohexanecarbonyloxy)acrolein with cyclopentadiene proceeded in EtCN at -75 degrees C to give the adducts in 88 % yield with 92 % exo and 91 % ee. The electron-donating property of the acyl group of the alpha-acyloxyacroleins increases the enantioselectivity due to the formation of strong intramolecular hydrogen bonding of the acyl group with a proton of the ammonium group in the transition state. This catalyst can be easily prepared in situ by mixing the commercially available chiral diamine and Tf2NH.