Darstellung von (3‐Amino‐1‐alkenyl)phosphonsäuren aus allylischen α‐ und γ‐Hydroxyphosphonaten. Sigmatrope Umlagerung von (1‐Azido‐2‐alkenyl)phosphonsäureestern

Synthesis of (3‐Amino‐1‐alkenyl)phosphonic Acids from Allylic α‐ and γ‐Hydroxyphosphonates. – Sigmatropic Rearrangement of Dialkyl (1‐Azido‐2‐alkenyl)phosphonates (3‐Azido‐1‐alkenyl)phosphonates 8 with R1 = H are prepared regioselectively by reaction of secondary (1‐hydroxy‐2‐alkenyl)phosphonates 3 with TPP/DEAD/HN3 and subsequent thermal 1,3‐rearrangement of the allylic α‐azidophosphonates 5 primarily formed. (3‐Azido‐1‐alkenyl)phosphonates 8 with R1 ≠ H are conveniently obtained from the regioisomeric tertiary 3‐hydroxy derivatives 4, which can be prepared either by allylic rearrangement of the corresponding α‐hydroxyphosphonates 3, or by NaBH4 reduction of the (3‐oxo‐1‐alkenyl) derivatives 7. The synthetic utility of the azido compounds 8 is demonstrated by their conversion into the (3‐amino‐1‐alkenyl)phosphonic acids 11 and the N,O‐protected derivatives 12 and 13, and to the saturated γ‐aminophosphonates 14.