Efficient Synthesis of Long‐wavelength Absorbing Cyanochlorophyll a Derivatives via Stereoselective Horner–Wadsworth–Emmons Reaction

• Published in: Bulletin of the Korean Chemical Society 2020, 41(5), , pp.504-512
• Main Authors: Wu, Huiqiang, Wang, Xiangmin, Liu, Yang, Zhao, Yu, Wang, Xinyue, Lee, Woo Kyoung, Shim, Young Key, Yoon, Il, Xu, Xinming, Li, Jiazhu
• Format: Article
• Language: English
• Subjects: Allomerization; Chlorin; Chlorophyll a; Cyanochlorin; Horner–Wadsworth–Emmons reaction; 화학
• ISSN: 1229-5949; 0253-2964; 1229-5949
• DOI: 10.1002/bkcs.11998

In this article, we report the stereoselective Horner–Wadsworth–Emmons reaction of reactive carbonyl‐substituted chlorophyll a derivatives with diethyl cyanomethylphosphonate. We found that the formyl or keto group at the chlorin periphery can react stereoselectively with phosphonate carbanions to produce a series of cyanomethylene‐substituted chlorins with predominantly E geometry. Considering that no consistent records are available in the literature on the results of the allomerization of methyl pyropheophorbide a, we propose a reliable process for the transformation of this chlorophyll derivative. Our methodology represents a simple and efficient way for the preparation of novel, differently functionalized long‐wavelength absorbing chlorins, those can be applied for photodynamic therapy, solar cells, and other relevant purposes. Stereoselective HWE reaction of reactive carbonyl substituted chlorophyll a derivatives with diethylcyanomethylphosphonate produced a series of cyanochlorophyll a derivatives with the long‐wavelength absorptions in the range of 677‐698 nm