Selective reduction of the nitrile in methyl 2-cyanomethyl-3-nitrobenzoate with DiBAL-H at low temperature, followed by cyclisation in situ gave 5-nitroisoquinolin-1-one, leading towards the lead PARP-1 inhibitor 5-AIQ. However, increasing steric bulk at the methylene switched reduction to the ester only, giving the corresponding benzaldehyde. Surprisingly, increasing steric bulk in the ester also allowed reduction of the ester prior to cyclisation, giving 5-nitroisoquinoline.
Keywords: Reductive cyclisation, isoquinolinone, isoquinoline, DiBAL-H
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