1,4-Dihydro-1,4-diarsinine: Facile Synthesis via Nonvolatile Arsenic Intermediates by Radical Reactions

Novel cyclic organodiarsenic compounds, 1,4-dihydro-1,4-diarsinines, were synthesized by radical reactions of
pentamethylcyclopentaarsine (1) and acetylenic compounds. The
radical reactions of 1 and acetylenic compounds such as
dimethyl acetylenedicarboxylate (2a) and 4-ethynylpyridine (2b)
in refluxing benzene with 2,2‘-azobis(isobutyronitrile) (AIBN;
5 mol %) under a nitrogen atmosphere provided the corresponding 1,4-dihydro-1,4-diarsinines (3). Formation of 1,4-dihydro-1,4-diarsinine was confirmed by 1H and 13C NMR
spectra and FAB-mass spectrometry. The structures of 3 were
confirmed as cis(e,e) forms by X-ray crystallography. This is a
facile synthesis of cyclic organodiarsenic compounds, in which
no volatile toxic intermediates such as arsenic chlorides and
arsenic hydrides were used. Moreover, this is the first example
of the synthesis of 1,4-dihydro-1,4-diarsinines.