Analysis of NRG ‘legal highs’ in the UK: identification and formation of novel cathinones

A large number of cathinone derivatives have shown a wide range of bioactive properties, attracting great interest from communities associated with pharmaceutical research. Some of these derivatives have gained popularity as so-called recreational 'legal highs' due to their availability on the Internet and high street shops. A previous study described the qualitative analysis of 24 'legal high' Energy-1 (NRG-1) and NRG-2 products obtained from 18 websites following the ban on mephedrone and derivatives in April 2010. The majority of these products contained a mixture of cathinones just carrying a new label. Here, three additional cathinone products have been detected; two from an NRG-1 sample and one from an NRG-3 sample. This report describes their identification. NRG-1 sample 1 consisted of a mixture of 4 cathinones namely 4-fluoromethcathinone (1), 1-(3,4-methylenedioxyphenyl)-2-(methylamino)pentan-1-one (pentylone, 2), 3,4-methylenedioxy-α-pyrrolidinobutyrophenone (MDPBP, 3) and 3,4-methylenedioxypyrovalerone (MDPV, 4). The sample labelled as NRG-3 (mislabelled with the chemical structure of mephedrone) consisted of a mixture of 4-methyl-α-pyrrolidinopropiophenone (MPPP, 5) and (2), whereas the remaining NRG-1 sample 2 (also mislabelled with the chemical structure of mephedrone) consisted of a mixture of (2) and (3). Qualitative analyses were carried out by GC-(EI/CI)-MS, NMR spectroscopy and confirmation by preparation of standards. The preparation of brominated precursors carrying the 3,4-methylenedioxyphenyl nucleus revealed extensive α,α-dibromination: the mass spectral and NMR data of these intermediates are also presented and discussed.