Older methods of quinoxaline reduction utilize active metals. More recently, methods for reduction of quinoxalines include those that are highly stereoselective or even enantioselective when using a chiral catalyst. The borane reduction method for making 1,2,3,4-tetrahydroquinoxalines has been shown to give cis isomers exclusively for quinoxalines unsubstituted at C5-C-8. We report that borane reduction can be made selective depending upon the nature of the substituent. Electron withdrawing substituents tend to make the pyrazine ring more susceptible to reduction, whereas electron donation lowers reactivity. Results for the reduction of a number of 2-methyl-3-phenylquinoxalines substituted at the C-6 and C-7 positions will be reported. Characterization was carried out with <sup>1</sup>H NMR and high-resolution mass spectrometry which helped prove expected structures of the unreduced and reduced products.

Borane-THF reduction of quinoxalines

ACS Fall 2021

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