An electrochemical multicomponent reaction toward C–H tetrazolation of alkyl arenes and vicinal azidotetrazolation of alkenes

The widespread use of tetrazoles in medicine, biology, and materials science continuously promotes the development of their efficient and selective syntheses. Despite the prosperous development of multicomponent reactions, the use of the most abundant and inexpensive chemical feedstocks, i.e., alkanes and alkenes, toward the preparation of diverse tetrazoles remains elusive. Herein, we developed an electrochemical multicomponent reaction (e-MCR) for highly efficient and selective C–H tetrazolation of alkyl arenes. When applied to alkenes, the corresponding vicinal azidotetrazoles were readily obtained, which were further demonstrated to be versatile building blocks and potential high-energy materials.


General procedures
were injected respectively into the glassware via syringes. The reaction mixture was stirred and electrolyzed at a constant current of 75 mA at room temperature for 23 minutes. Following concentration in vacuo, the crude residue was subjected to flash column chromatography on silica gel to yield the desired products.
Method C: General procedure for the electrochemical synthesis of vicinal azidotetrazoles (constant cell-potential electrolysis) S6 In an oven-dried undivided three-necked glassware (25 mL) equipped with a stirring bar, n Bu4NClO4 (0.3 mmol) was added. The glassware was equipped with a graphite plate (15 mm × 15 mm × 1 mm) as the anode and a platinum plate (15 mm × 15 mm × 0.3 mm) as the cathode. Under the protection of N2, olefin substrates (0.3 mmol), TMSN3 (2.5 equiv.), CH3CN (10 mL), and HFIP (0.8 mL) were injected respectively into the glassware via syringes. The reaction mixture was stirred and electrolyzed at a constant cell potential of 2.8 V at room temperature for 4 h.
Following concentration in vacuo, the crude residue was subjected to flash column chromatography on silica gel to yield the desired products.
S7 Table S1. Screening of electrode materials Table S2. Screening of current S8   Table S3. Screening of the amount of TMSN3

Procedure for control experiments using chemical oxidants
In an oven-dried schlenk (10 mL) equipped with a stirring bar, n Bu4NClO4 (

Unsuccessful substrates
Unsuccessful substrates of C-H tetrazolation are shown in Table S5. For S1-S5, S13-S15, these reaction systems were clean but the yields were generally low. For S7, the desired tetrazole cannot be separated from the C-H acetylation byproduct. For S8-S12, S20-S22, these reactions only afforded complex reaction mixtures. For S6, S16-S18, low conversions were obtained as there were a lot of raw materials recovered. For S19, the desired C-H tetrazolization reaction did not occur at all. For S23 and S24, no formation of C-H tetrazolization products was detected. Unsuccessful substrates of vicinal azidotetrazolation are shown in Table S6.

Radical clock experiment
Following the standard procedure for the synthesis of vicinal azidotetrazoles and azidoacetamides using 1-(2-phenylcyclopropyl)vinyl)benzene (0.3 mmol) as the starting material. After work-up, the crude mixture was purified using column chromatography to afford 55.

Probing arene radical cations
The procedure is the same as Method A

H2 detection experiment
We have carried out the headspace GC analysis of the reaction mixture and confirmed the formation of H2 both in the tetrazolation and azidotetrazolation.

TG-DSC experiments
The TG-DSC curves of compound 25, 27, 42 were measured at N2 flow rate of 20 mL•min -1 , heating rate of 10.0 ℃• min -1 and temperature range of RT to 400 ℃.
Crucible with aluminum lid was used as the sample tank.