Organophosphorus compounds. Part IX: Decomposition of ω‐dimethylaminoalkyl methylphosphonofluoridates and isomerization of 2‐dipropylaminoethyl methylphosphonofluoridothionate

The decomposition product of 2-dimethylaminoethyl methylphosphonofluoridate (IV, n = 2) was identified as 1,1,4,4-tetramethylpiperazinium bis-(methylphosphonofluoridate) (VI). In hexadeuteriodimethyl sulfoxide (60°), the first-order rate of decomposition of IV (n = 2) is ∼ 830 times greater than the rate of the analogous decomposition of 2-dimethylaminoethyl isopropyl methylphosphonate (XV). The hitherto unreported O-2-dimethylaminoethyl methylphosphonofluoridothioate (IX, R = Me) degrades on heating to 1,1,4,4-tetramethylpiperazinium bis(methylphosphonofluoridothioate) (XIII, R = Me), whereas IX (R = n-Pr) rearranges to S-2-di-n-propylaminoethyl methylphosphonofluoridothioate (XI, R = n-Pr). Arguments are put forward that the decomposition reactions of IV (n = 2), XV and IX (R = Me), as well as the rearrangement of IX (R = n-Pr) proceed via a 1,1-dialkylaziridinium cation. The decomposition of 3-dimethylaminopropyl methylphosphonofluoridate (IV, n = 3) at 40° gives a polymeric salt [VIII, Y = OPO(Me)F].