Storch Golo, Spallek Markus J, Rominger Frank, Trapp Oliver
Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany).
Chemistry. 2015 Jun 8;21(24):8939-45. doi: 10.1002/chem.201500524. Epub 2015 May 4.
1,3,4,6-Tetraketones typically undergo keto-enol tautomerism forming bis-enols stabilized by intramolecular hydrogen bonding in two six-membered rings. However, 1,3,4,6-tetraketones derived from the terpene ketone camphor and norcamphor exist as isomers with two distinguishable modes of intramolecular hydrogen bonding, namely, the formation of six- or seven-membered rings. The structural requirements for this so far unknown behavior were investigated in detail by synthesis and comparison of structural analogues. Both isomers of such 1,3,4,6-tetraketones were fully characterized in solution and in the solid state. Intriguingly, they slowly interconvert in solution by means of tautomerism-rotation cascades, as was corroborated by DFT calculations. The influence of temperature and complexation with the transition metals Pd, Rh, and Ir on the interconversion process was investigated.
1,3,4,6-四酮通常会发生酮-烯醇互变异构，形成通过两个六元环内的分子内氢键稳定的双烯醇。然而，源自萜烯酮樟脑和降樟脑的1,3,4,6-四酮以具有两种可区分的分子内氢键模式的异构体形式存在，即形成六元或七元环。通过合成和结构类似物的比较，详细研究了这种迄今为止未知行为的结构要求。此类1,3,4,6-四酮的两种异构体在溶液和固态中均得到了充分表征。有趣的是，正如DFT计算所证实的那样，它们在溶液中通过互变异构-旋转级联缓慢地相互转化。研究了温度以及与过渡金属钯、铑和铱的络合对互变过程的影响。
