Efficient synthesis of substituted 1‐dimethylamino or 1‐methylthio but‐3‐enylidene‐bis‐phosphonates,via the [2,3]‐sigmatropic rearrangement of related transient ammonium or sulfonium ylides

New variously substituted 1‐dimethylamino or 1‐methylthio but‐3‐enylidene‐bis‐phosphonates have been prepared from readily availableα‐dimethylamino or α‐methylthio methylene‐bis‐phosphonates by postulated 2,3]‐Wittig rearrangements of the corresponding N‐ or S‐allylic intermediate ylides. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 281–289, 1999