Regioselective 1,3‐dipolar cycloaddition of Cyanogen N,N′‐dioxide (2) to trimethylsilyl enol ethers 3a‐d, 6 and 7 gave the corresponding 5,5′‐bis(trimethylsilyloxy)‐3,3′‐Δ2‐biisoxazolines which upon short heating with 10% hydrochloric acid afforded 3,3′‐biisoxazoles 5a‐d, 8 and 9. Only the intermediate 5,5′‐bis(trimethylsilyloxy)‐derivative 4a was isolated and studied. Reaction of 2 with vinyl methyl ketone (10) gave biisoxazoline 11 which by oxidation with γ‐manganese dioxide gave biisoxazole 12.