GC–MS and GC–IR analysis of methylenedioxyphenylalkylamine analogues of the psychoactive 25X-NBOMe drugs

Twelve secondary amines structurally similar to NBOMe drugs were synthesized and analyzed using gas chromatography–mass spectrometry and vapor-phase infrared spectroscopy. These compounds contain a methylenedioxy group fused to the aromatic ring of the phenethyl moiety. One subseries are N-methoxybenzyl analogues of MDA; another subseries have bromine and two methoxy groups on the benzyl side. The compounds are not known drugs of abuse, and the study provides data to distinguish them from current NBOMe drugs. The elution order on a specific GC phase was determined for regioisomers, and characteristic fragmentation patterns in mass spectra and infrared spectra confirmed substitution positions.

Study at a glance

Abstract

Abstract Twelve secondary amines representing structural analogues of the classic NBOMe category of novel psychoactive substances were prepared and evaluated in GC-EI-MS and vapor phase GC–IR studies. These compounds all contain the methylenedioxy group fused with the aromatic ring of the phenethyl moiety in the classic NBOMe chemical framework. One subseries of analogues, the three regioisomeric phenylisopropylamines, can be viewed as the N-methoxybenzyl analogues of 3,4-methylenedioxyamphetamine (MDA). Another subseries of three regioisomers contains the bromine and two methoxy groups at positions 2, 4 and 5 of the benzyl side of the molecule. The GC properties and the correlated EI-MS fragmentation products of these amines and some trifluoroacetamide derivatives were evaluated and compared to the traditional drug of abuse 25B-NBOMe. The compounds in this study are not currently known drugs of abuse and this proactive investigation provides data for differentiation of these analogues from the current NBOMe drugs of abuse. The observed GC elution order for the regioisomeric methoxybenzyl analogues on an Rxi®-17Sil MS phase was the 2-methoxy isomer eluting before the 3-substituted isomer, and the 4-substituted isomer eluting last. A similar comparison for the position of methylenedioxy fusion shows the 2,3-substituted isomer eluted before the 3,4-substituted isomer. All these secondary amines undergo EI fragmentation yielding the iminium cation via C–C bond cleavage of the phenethyl chain and the two benzylic cationic species. The mass spectra for the trifluoroacetyl derivatives in the bromodimethoxybenzyl substituted subseries provided additional structural information based on unique fragmentation processes. These characteristic ions are formed following initial hydrogen rearrangement within the molecular radical cation. The vapor phase infrared (vpIR) spectra confirm the position of substitution of the methylenedioxy, methoxy and bromodimethoxy groups.