Acid-Mediated Electrocyclic Domino Transformations of 5,5-Disubstituted 1-Amino-1-azapenta-1,4-dien-3-ones into Dihydrospiroindenepyrazole and Dihydroindenodiazepine Derivatives
作者:Nugzar Ghavtadze、Roland Fröhlich、Ernst-Ulrich Würthwein
DOI:10.1021/jo900270e
日期:2009.6.19
as a dicationic cyclization of a pentadien-1-one (“superelectrophilic solvation”), where one of the double bonds is part of an aromatic ring and a subsequent rearrangement to form an (monocationic) iminium ion, which either cyclizes to give five-membered spiro ring systems (compounds 5) or tricyclic dihydroindenodiazepine derivatives 6. Hückel- and Möbius-type transition states of the electrocyclization
三氟甲基取代的1-氨基-1-azapenta-1,4-二烯-3-酮4在三步法中可从丙酮酸酯1中以高收率获得,并经过级联反应,其中包括用2处理后的两个电环化反应。大量过量的三氟甲磺酸生成新的二氢螺并茚并吡唑5a - o和二氢茚并二氮杂6a - j。我们根据量子化学计算将这一反应序列解释为戊二烯-1-酮的特殊环化反应(“超亲电溶剂化”),其中双键之一是芳环的一部分,随后进行重排形成一个(单阳离子)亚胺离子,它可以环化成五元螺环系统(化合物5)或三环二氢茚并二氮杂卓衍生物6。考虑到NICS计算的结果,讨论了电环化反应的Hückel型和Möbius型过渡态。一个1-氨基-1-戊-1,4-二烯-3-酮4和几种二氢螺并茚并吡唑5和二氢茚并二氮杂6 可以通过X射线衍射来表征。