THERMAL REARRANGEMENT OF TRICHLOROACETIMIDIC ESTERS OF ALLYLIC ALPHA-HYDROXYPHOSPHONATES - A CONVENIENT WAY TO (3-AMINO-1-ALKENYL)PHOSPHONIC ACIDS

Secondary dialkyl (1-hydroxy-2-alkenyl)phosphonates 3 are reacted with trichloroacetonitrile to yield the new (1-dialkoxyphosphoryl-2-alkeny l) 2,2,2-trichloroacetimidates 4, which in boiling toluene (for compou nds 4b-g) or xylene (for 4a) are transformed regiospecifically to the loro-N-(3-dialkoxyphosphoryl-2-alkenyl)-acetamides 5. The [3,3] sigmat ropic rearrangement of compounds 4 occurs with high E-stereoselectivit y (compounds 5a-e, and g), or stereospecifically [(E)-5f]. Deprotectio n of the rearrangement products 5 with hydrochloric acid/propylene oxi de affords the (3-amino-1-alkenyl)phosphonic acids 6 in excellent over all yields.