Ionic hydrogenation of benzofurans
Benzofurans are arranged in the order 2-methylbenzofuran > 3-methylbenzofuran > benzofuran with respect to the case with which they undergo ionic hydrogenation. Benzofuran and 2-methylbenzofuran are protonated in the 3 position of the heterocyclic ring, whereas 3-methylbenzofuran is protonated in the 2 position. Individual monodeuterated 2,3-dihydrobenzofurans can be obtained in high yields by ionic hydrogenation.