We present a contemporary mechanistic description of the light-driven conversion of cyclopropenone containing enediyne (CPE) precusors to ring-opened species amenable to further Bergman cyclization and formation of stable biradical species that have been proposed for use in light-induced cancer treatment. The transformation is rationalized in terms of (purely singlet state) Norrish type-I chemistry, wherein photoinduced opening of one C–C bond in the cyclopropenone ring facilitates non-adiabatic coupling to high levels of the ground state, subsequent loss of CO and Bergman cyclization of the enediyne intermediate to the cytotoxic target biradical species. Limited investigations of substituent effects on the ensuing photochemistry serve to vindicate the experimental choices of Popik and coworkers (J. Org. Chem., 2005, 70, 1297–1305). Specifically, replacing the phenyl moiety in the chosen model CPE by a 1,4-benzoquinone unit leads to a stronger, red-shifted parent absorption, and increases the exoergicity of the parent → biradical conversion.

我们提出了对含烯二炔（CPE）前体的环丙烯酮转化为开环物质的光驱动转化的当代机制描述，该转化适合于进一步伯格曼环化和稳定双自由基物质的形成，这些双自由基物质已被提议用于光诱导癌症治疗。该转变根据（纯单线态）Norrish I 型化学合理化，其中环丙烯酮环中一个 C-C 键的光致打开促进了与高水平基态的非绝热耦合，随后损失了 CO 和 Bergman烯二炔中间体环化为细胞毒性目标双自由基物质。对取代基对随后光化学影响的有限研究证明了 Popik 和同事的实验选择是正确的（J. 组织。化学., 2005,70，1297–1305）。具体来说，用 1,4-苯醌单元替换所选模型 CPE 中的苯基部分会导致更强的红移母体吸收，并增加母体→双自由基转化的放热性。