Selective C‐7 Functionalization of Phenanthridines by Microwave‐Assisted Claisen Rearrangements of 8‐Allyloxyphenanthridines

Carbon‐carbon bond formation in the phenanthridine 7‐position was achieved by microwave‐assisted Claisen rearrangement of 8‐allyloxyphenanthridines. The reactions took place with excellent regioselectivity and high chemical yields. If the 7‐position was substituted, rearrangement to C‐9 took place, but the reaction occurred less readily. Rearrangements of 8‐allyloxy‐5,6‐dihydrophenanthridines (phenanthridines with a saturated B‐ring) gave a mixture of 7‐ and 9‐substituted products. The experimental results were supported by DFT (density functional theory) calculations.