Synthesis and Decomposition of Two Cyclic (Four-Ring) Azo Compounds (Δ1-1,2-Diazetines)

Article abstract of DOI:10.1021/jo00072a021

The Δ¹-1,2-diazetines 1 and 2 have been synthesized in three steps from N-methyltriazolinedione (MeTAD) and the olefins (adamantylideneadamantane, Ad=Ad, for 1; 7-norbornylidene-7-norbornane for 2).Diazetidine 3 (from Ad=Ad + MeTAD) undergoes ring expansion to a pyrazolidine derivative, 5 (subsequently converted to a novel pyrazoline, cyclic (five-ring) azo compounds 6).The structurally-related N-methylaminocarbonyl diazetidine 4 undergoes acid-catalyzed ring contraction to N-aminoaziridine derivative 7a.Compound 7a and the corresponding N-aminoaziridine derivative 7b undergo oxidative ring expansion to afford diazetine 1, accompanied by olefin (Ad=Ad).Efforts to extend this novel synthesis of diazetines to other N-aminoaziridines (8, 9a, 9b, 10) were unsuccessful, affording only the deazetation product, olefin.Thermal decomposition of diazetine 1 at 137 deg C in dodecane (t_1/2 = 1.5 h) proceeds by two paths: ring-opening to adamantanone azine and deazetation to the olefin Ad=Ad; azine/olefin = 1.9/1.For diazetine 2, k_overall is 60-fold slower than for 1 and azine/olefin = 1/14.Diazetine 1 is rapidly converted to olefin (Ad=Ad) at 25 deg C by 10 molpercent of Ar3N(.+)*<(p-BrC6H4)3N(.+)*SbF6(1-)>, thought to occur by an electron transfer chain process; diazetine 2 is inert to these conditions.Relative rates of nitrogen loss for 1, 2, and tetramethyldiazetine (15c) at 137 deg C are 1:0.05:3.Some aspects of mechanism of thermal and catalyzed decomposition of diazetines are discussed.