Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China.
J Org Chem. 2012 Sep 21;77(18):8206-19. doi: 10.1021/jo301573e. Epub 2012 Sep 6.
An oxidative addition of primary alkoxyls into two sites of N-confused porphyrin (NCP) has been accomplished by means of alcohols in the presence of a stoichiometric amount of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The resulting aromatic monocationic species 1-R(3) (R = Me, Et) were characterized by the NMR and, in the case of triethoxy-NCP, by monocrystal X-ray diffraction analysis. One alkoxy group is located in position 3, on the macrocycle's perimeter, while two -OR moieties are attached to the internal carbon (position 21) of the confused pyrrole. The 3-EtO-21-Cl-NCP 2, which is formed as a byproduct, was also structurally characterized by means of X-ray diffraction. Reduction of 3-RO-21-(RO)(2)-NCP with hydrazine hydrate gave selectively a neutral and intrinsically chiral 3,21-bis(alkoxy)NCP 3-R(2). Dealkylation of the externally bonded 3-OR fragment under basic conditions leading to a zwitterionic aromatic 3-oxo-species 4-R(2), which still possesses the internal ketal functionality, was established by the NMR and X-ray diffraction methods. An unprecedented transetherification for the internal alkoxyl of 3-R(2) can be achieved under very mild conditions and without catalyst. One of the alkoxyl-exchange products, i.e., 3-ethoxy-21-methoxy-NCP, was characterized by the X-ray diffraction method. The substitution proceeds via an associative (S(N)2) mechanism resulting in an inversion of the chirality of 3-RR', which was shown by means of the NMR and chirooptical methods.
通过在化学计量量的 2,3-二氯-5,6-二氰基-1,4-苯醌（DDQ）存在下使用醇，实现了伯烷氧基到 N-稠合卟啉（NCP）两个位置的氧化加成。所得芳香一价阳离子物种 1-R(3)（R = Me, Et）通过 NMR 进行了表征，在三乙氧基-NCP 的情况下，通过单晶 X 射线衍射分析进行了表征。一个烷氧基位于大环的外围的 3 位，而两个 -OR 部分则连接到稠合吡咯的内部碳（21 位）上。作为副产物形成的 3-EtO-21-Cl-NCP 2 也通过 X 射线衍射进行了结构表征。肼水合还原 3-RO-21-（RO）（2）-NCP 选择性地得到了中性和内在手性的 3,21-双（烷氧基）NCP 3-R(2)。通过 NMR 和 X 射线衍射方法确定，在碱性条件下脱除外部键合的 3-OR 片段，得到具有内部酮缩醇官能团的两性离子芳族 3-酮物种 4-R(2)。在非常温和的条件下且无需催化剂，可以实现 3-R(2)的内部烷氧基的空前转醚化。其中一个烷氧基交换产物，即 3-乙氧基-21-甲氧基-NCP，通过 X 射线衍射方法进行了表征。取代通过缔合（S(N)2）机制进行，导致 3-RR'的手性反转，这通过 NMR 和旋光方法证明了。
