One-pot assembly of functionalized (m-terphenyl-4'-yl)isoquinolines from 1-methylisoquinoline and electrophilic acylacetylenes

The relative reactivity of deprotonated CH₃ group and nitrogen atom of 1-methylisoquinoline towards electrophilic triple bond crucially depends on the acetylene structure and the reaction conditions. 1-Acyl-2-arylacetylenes react with 1-methylisoquinoline in a 2 : 1 molar ratio (34 mol% KOH · 0.5 H₂O, H₂O/MeCN, 55–60 °C, 24–48 h) to give 1-[5'-(het)aryl-m-terphenyl-4'-yl]isoquinolines in 28–51% yields and 1-[6'-acyl-5'-(het)aryl-m-terphenyl-4'-yl]isoquinolines in trace to 11% yields. The minor product (proved by X-ray) results from 1,3-shift of the acyl group in the carbanionic intermediate.