Hemoglobin-inorganic hybrid nanoflowers: Synthesis and applications for carbene N-H insertion reaction

Hemoglobin (Hb) is a hemoprotein containing iron porphyrin, which can catalyse a variety of unnatural reactions. Due to its poor reusability and stability, in this study, we developed a new method to prepare Hb-Cu-3(PO4)(2) hybrid nanoflowers (HNFs) by co-incubating Hb with Cu2+. This immobilized Hb was used to catalyse the synthesis of ethyl N-phenylglycinate via the carbene N-H insertion reaction. Under the optimum reaction conditions (aniline 1 mmol; ethyl diazoacetate 1 mmol; deionized (DI) water 10 ml; catalyst (protein content: 15 mg); sodium hydrosulfite 25 mg; 25 degrees C; 12 h), the catalytic yield of Hb-Cu-3(PO4)(2) HNFs reached as high as 87% and that of free Hb was 74%. In addition, Hb-Cu-3(PO4)(2) HNFs can maintain a high catalytic performance after 15 cycles and still achieve yields close to 70% of the initial yield after 60 days of storage, indicating that Hb-Cu-3(PO4)(2) HNFs have a high potential for application in Hb-catalysed organic reactions.