Intramolecular Amine-Induced [1,3]-Sigmatropic Rearrangement in the Reactions of Aminophosphinites or Phosphites with Elemental Sulfur or Selenium

Ether- and thioether-functionalized cyclodiphosphazanes cis-[tBuNP(OCH2CH2EMe)]2 (E = O, 1; E = S, 2) react
with 2 equiv of elemental sulfur or selenium to produce dichalcogenides cis-[tBuNP(E)(OCH2CH2EMe)]2 (4−6),
whereas the similar reaction of amine-functionalized cyclodiphosphazane cis-[tBuNP(OCH2CH2NMe2)]2 (3) with
elemental chalcogen results in the formation of thio- or selenophosphates trans-[tBuNP(O)(ECH2CH2NMe2)]2 (E =
S, 7; E = Se, 8) through [1,3]-sigmatropic rearrangement. The X-ray crystal structure of 8 confirms the rearranged
product as the trans isomer with a planar P2N2 ring. The equimolar reaction of P(OCH2CH2OMe)3 (9) with elemental
sulfur or selenium produces the simple sulfide and selenide EP(OCH2CH2OMe)3 (E = S, 11; E = Se, 12)
derivatives, respectively. In contrast, the reaction between P(OCH2CH2NMe2)3 (10) and S or Se furnishes the
rearranged products (13 and 14). The rearrangement reaction was monitored by 31PNMR spectroscopy, which
confirms the formation of selenophosphinic acid as the first step of the rearrangement. The [1,3]-sigmatropic
rearrangement presumably takes place through chalcogen−nitrogen interactions.