It has recently been reported that the loss of two consecutive benzyl radicals occurs selectively from deuterated isomeric dihydroxybenzene dibenzyl ethers and trihydroxybenzene tribenzyl under ESI/CID conditions.1 The regiospecificity of the fragmentation pattern in the mass spectrum of each isomer and related isotopomers correlated well with DFT calculations.1 The synthesis of tetra(benzyloxy)benzene isomers 1, 2 and 3, labeled selectively with D0, D2, D5 and D7 benzyl moieties, and the subsequent investigation by ESI and EI mass spectrometry is presented. Starting with the appropriate di- or trihydroxy acetophenone these desired tetra(benzyloxy)benzene isomers were prepared through a series of reactions starting with one or more benzylation steps using the appropriate benzyl bromide and potassium carbonate in dry DMF. Subsequent conversion of the ketone moiety in a Baeyer-Villiger rearrangement followed by hydrolysis affords a phenol that can again be selectively benzylated. Iteration of this pattern of reactions provided compounds 1-3 and additional isotopomers. The sodiated tetra(benzyloxy)benzenes were modeled using DFT and HF calculations. The lowest energy conformation was found at a lower level of theory, while fragmentation patterns were studied with larger basis sets. A comparison of the mass spectrometric results and the DFT/HF calculations is presented, along with a complete characterization of all products using 1H and 13C NMR.

Synthesis of tetra(benzyloxy)benzenes for mass spectrometry studies

249th National Meeting (2015)

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