Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
J Am Chem Soc. 2020 May 27;142(21):9718-9724. doi: 10.1021/jacs.0c02221. Epub 2020 May 12.
Although diazoalkanes are important carbene precursors in organic synthesis, a comprehensive mechanism of photochemical formation of carbenes from diazoalkanes has not been proposed. Synergies of experiments and computations demonstrate the involvement of higher excited singlet states in the photochemistry of diazoalkanes. In all investigated diazoalkanes, excitation to S results in nonreactive internal conversion to S. On the contrary, excitation to higher-lying singlet states (S, n > 1) drives the reaction toward a different segment of the S/S conical intersection seam and results in nitrogen elimination and formation of carbenes.
尽管重氮烷烃是有机合成中重要的碳烯前体，但目前尚未提出重氮烷烃光化学形成碳烯的综合机制。实验和计算的协同作用证明了较高激发单线态在重氮烷烃光化学中的参与。在所研究的所有重氮烷烃中，激发到 S 态导致非反应性的内转换到 S 态。相反，激发到更高的单线态（S，n>1）将反应推向 S/S 交叉 seam 的不同区域，并导致氮消除和碳烯的形成。
