[1423-60-5] · C4H4O · 3-Butyn-2-one · (MW 68.08)
(conjugate acceptor, dienophile)
Physical Data: bp 85 °C; d 0.87 g cm-3.
Solubility: sol chloroform, diethyl ether, ethanol.
Form Supplied in: neat liquid; widely available.
Handling, Storage, and Precautions: is a highly toxic, flammable liquid. It is also a severe lachrymator. It may be fatal if inhaled, swallowed, or absorbed through the skin. When handling this material, appropriate protective clothing, safety goggles, and an approved respirator should be worn. The material should be refrigerated when stored. Use in a fume hood.
3-Butyn-2-one has been employed successfully in Pictet-Spengler4 reactions, Diels-Alder and ene reactions,5 1,3-dipolar cycloadditions,6 and cyclotrimerizations.7 A regioisomeric mixture of isoxazoles is produced when 3-butyn-2-one is reacted with bromonitrile oxide (generated in situ).7 The major product is an intermediate in the synthesis of the b-agonist broxaterol.
A variety of nucleophiles successfully add to 3-butyn-2-one (and related alkynones).8,9 Attempts to use 3-butyn-2-one in Robinson annulations have not been very successful.10 Nitro-stabilized carbanions add well using phase transfer catalysis (eq 1), yielding preferentially the (E) isomer.11
Trialkylboranes12 and Tris(trimethylsilyl)aluminum13 efficiently transfer alkyl and trimethylsilyl groups, respectively, in a conjugate fashion.
Asymmetric reduction has been achieved using several different reagents.14-17 Many other alkynones are reduced with high levels of asymmetric induction and the best result to date with 3-butyn-2-one was achieved using either Eapine- or Prapine-Borane.14,18 For more sterically hindered alkynones, (+)-B-Chlorodiisopinocampheylborane works well.14 Reduction of the tosylhydrazone of 3-butyn-2-one produces 1,2-butadiene in reasonable yield.19
Monash University, Clayton, Victoria, Australia