Bacteriochlorins – Nature’s near-infrared (NIR) chromophores – are distinguished by an intense ($𝜀$$\sim$10⁵ M${}^{-1}$cm${}^{-1})$ long-wavelength absorption band in the $\sim$700–1000 nm. The development of routes to prepare synthetic, tailorable bacteriochlorins holds promise for multiple disciplines where NIR-light-promoted photoactivity is of interest. A de novo route to bacteriochlorins equipped with a stabilizing gem-dimethyl group in each pyrroline ring was discovered in 2003. Continued development in this arena over 20 years has led to additional routes as well as methods to install substituents at selected positions about the perimeter of the macrocycle. The present paper reports studies that highlight substantial limitations of existing synthetic routes, including stymied access to multi-bacteriochlorin arrays and the inability to install (in a rational way) distinct groups at opposite sides of the macrocycle. The origins of the limitations are traced to particular stages of the chemistry ranging from derivatizing pyrroles, creating pyrrolines, constructing and elaborating dihydrodipyrrins, coupling dihydrodipyrrins, and forming macrocycles. Through exploration of a dozen aspects of bacteriochlorin syntheses, 60 new compounds (and nine known compounds via improved syntheses) have been prepared and characterized; the data include 20 single-crystal X-ray diffraction analyses. The research taken together points to areas of focus to fulfill the promise of this fascinating class of compounds.

菌绿素——自然界的近红外（NIR）发色团——以强烈的（$𝜀$$～$10 ^5M _${}^{-1}$厘米${}^{-1}）$长波长吸收带$～$700–1000 纳米。制备合成的、可定制的菌绿素的路线的开发为对近红外光促进光活性感兴趣的多个学科带来了希望。从头开始2003 年，人们发现了在每个吡咯啉环中配备有稳定偕二甲基基团的菌绿素的路线。20 多年来，这一领域的持续发展催生了更多的路线以及在大环周边的选定位置安装取代基的方法。本文报道的研究强调了现有合成路线的实质性局限性，包括阻碍多菌绿素阵列的获得以及无法（以合理的方式）在大环的相对侧安装不同的基团。限制的根源可追溯到化学的特定阶段，从衍生化吡咯、产生吡咯啉、构建和精制二氢二吡林、偶联二氢二吡林以及形成大环。通过对菌绿素合成的十几个方面的探索，已制备并表征了 60 种新化合物（以及通过改进合成而得到的 9 种已知化合物）；数据包括 20 个单晶 X 射线衍射分析。综合研究指出了实现这一类令人着迷的化合物的前景的重点领域。