Nitration Under Continuous
Flow Conditions: Convenient
Synthesis of 2‑Isopropoxy-5-nitrobenzaldehyde, an Important
Building Block in the Preparation of Nitro-Substituted Hoveyda–Grubbs
Metathesis Catalyst
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Abstract
Herein, we describe the use of continuous flow chemistry
for selective,
efficient and reproducible nitration of 2-isopropoxybenzaldehyde to
produce the desired 2-isopropoxy-5-nitrobenzaldehyde, an important
building block in the preparation of a ligand of nitro-substituted
Hoveyda–Grubbs metathesis catalyst. Nitration was done with
red fuming HNO<sub>3</sub>, and this challenging and hazardous process
was performed using a flow-through silicon-glass microreactor equipped
with a set of temperature sensors, and with a productivity of 13 g/h,
providing us with a reproducible chemical process amenable for production
of sufficient quantities of 2-isopropoxy-5-nitrobenzaldehyde for ongoing
large-scale synthesis of nitro-substituted Hoveyda–Grubbs metathesis
catalyst