Synthesis of Novel (Phenylalkyl)amines for the Investigation of Structure?Activity Relationships,Part 3

An easy and efficient pathway for the preparation of 4‐ethynyl‐2,5‐dimethoxyphenethylamine (=4‐ethynyl‐2,5‐dimethoxybenzeneethanamine; 2C‐YN; 1 ) was developed, an ethynyl analogue of the potent 5‐HT_2A/C agonists, e.g., 4‐iodo‐2,5‐dimethoxy‐amphetamine (DOI; 2b ). The ethynyl moiety was introduced by a Pd‐catalyzed Sonogashira reaction of (trimethylsilyl)ethyne with N‐(trifluoroacetyl)‐protected 4‐iodo‐2,5‐dimethoxyphenethylamine ( 7 ) in almost quantitative yield within only 1 h. Removal of the Me₃Si group was accomplished with Bu₄NF. Final N‐deprotection by NaOH treatment afforded the novel phenethylamine 1 in an overall yield of 88%.