UR-144 in products sold via the Internet: identification of related compounds and characterization of pyrolysis products

The synthetic cannabinoid, UR-144 ((1-pentyl-1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)methanone), was identified in commercial 'legal high' products (herbal, resin, and powder). Along with this, six related compounds were detected. The most abundant one (2.1) was identified as 4-hydroxy-3,3,4-trimethyl-1-(1-pentyl-1H-indol-3-yl)pentan-1-one, a product of the electrophilic addition of water to the cyclopropane moiety in UR-144. Compound 2.1 was found to be undergo cyclisation which leads to the formation of two additional interconvertable compounds (2.3, tentatively identified as 1-pentyl-3-(4,4,5,5-tetramethyl-4,5-dihydrofuran-2-yl)-1H-indole which is stable only in absence of water and also observed as GC artifact) and 2.2, a protonated derivative of 2.3 which is formed in acidic solutions. The remaining compounds were identified as possible degradation products of the group 2 compounds (4,4,5,5-tetramethyldihydrofuran-2(3H)-one and 1-pentylindoline-2,3-dione) and intermediates or by-products from the synthesis of UR-144 ((1H-indol-3-yl)(2,2,3,3-tetramethylcyclopropyl)methanone, 1-pentyl-1H-indole and 1-(1-pentyl-1H-indol-3-yl)hexan-1-one). Pyrolysis of herbal products containing the group 2 compounds or UR-144 resulted in the formation of 3,3,4-trimethyl-1-(1-pentyl-1H-indol-3-yl)pent-4-en-1-one (3). This was confirmed by separate pyrolysis of 2.1 and UR-144. Also, the two additional minor compounds, 1-(1-pentyl-1H-indol-3-yl)ethanone and 1-(1-pentyl-1H-indol-3-yl)propan-1-one, were detected. Pathways for these transformations are presented.