Pro‐aromatic Dihydroquinazolinones – From Multigram Synthesis to Reagents for Gram‐scale Metallaphotoredox Reactions

Abstract

Dihydroquinazolinone (DHQZ) has recently been harnessed as a ketone‐derived pro‐aromatic reagent extensively employed in (metalla)photoredox reactions as versatile group transfer agents. In this work, we outline a column chromatography‐free protocol for the multigram‐scale synthesis of pro‐aromatic DHQZs as well as its use in a gram‐scale nickel/photoredox dual‐catalyzed cross‐coupling in single‐batch, photoflow, and simultaneous multiple smaller batches. While the single‐batch approach leveraged moderate yields, a simple plug‐flow photoreactor also exhibited amenable productivity (up to 45% yield) despite the use of a heterogeneous base. Meanwhile, performing the metallaphotoredox‐catalyzed reaction in multiple smaller batches in an improvised photoreactor facilitated high yields of up to 59% and good reproducibility, implying a convenient alternative in the absence of photoflow setups.