Abstract
A metal-free, regioselective C-H functionalization of heteroaromatic N-oxides has been developed. The method enables the synthesis of various benzylated and alkynylated N-heterocycles in a transition-metal-free manner employing organosilanes as coupling partners. The unanticipated reactivity has been exploited for the synthesis of a number of symmetrical disubstituted acetylenes from ethynyltrimethylsilane via carbon-silicon bond metathesis.
Highlights
C1-benzylated isoquinolines represent the privileged core of a number of alkaloids and drugs with a wide variety of structures.[3]
2015, our group revealed a regioselective, metal-free crosscoupling of quinoline N-oxides with boronic acids and was the first instance of Petasis reaction application in the direct C−H functionalization of heterocycles.[9]
With our continuing research interest in the area,[13] we envisioned that an oxidant-free, metal-free direct C−H bond functionalization using organosilanes as coupling partners for the synthesis of 1-benzylisoquinolines would be highly desired (Scheme 1d)
Summary
2015, our group revealed a regioselective, metal-free crosscoupling of quinoline N-oxides with boronic acids and was the first instance of Petasis reaction application in the direct C−H functionalization of heterocycles.[9]. 2015, our group revealed a regioselective, metal-free crosscoupling of quinoline N-oxides with boronic acids and was the first instance of Petasis reaction application in the direct C−H functionalization of heterocycles.[9] Very recently, Murakami and co-workers reported a one-step conversion of pyridine N- Organic Letters coupling reactions with azaarene 1-oxides.[12] But it is quite evident that, despite being an important building block in the biosynthesis of naturally occurring alkaloids and a privileged scaffold among pharmaceuticals, metal-free functionalization of C−H bonds of isoquinoline remains comparatively underexplored.
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