The intramolecular ene reactions of some unsaturated acyloins

The reaction of 3β-tosyloxy-5α-cholesta-5,6β-diol with potassium t butoxide in t-butanol has been further investigated. 5β-Hydroxy-4,5-secocholest-3-en-6-one was synthesised. It was shown to undergo an ene reaction in decalin in a sealed tube at 200°C to give primarily 3β-methyl-A-nor-5β-cholestan-5-o1 -6-one and 6β-hydroxy-4(5-6α) abeo-cholestan-5-one. These primary products were further modified under the reaction conditions to give 3-methyl-B-nor-5β-cholest-2-en-4-one and 5β-cholestan-5-ol-6-one respectively. The cyclohexane analogue, 3-methyl-3-(3-butenyl)-2-hydroxy-cyclohexanl- one was synthesised. Heating under reflux in decalin gave 3β,7aβ-dimethyl- 3aβ-hydroxy-octahydro-4H-inden-4-one;5β,7aβ-dimethyl-3aβ-hydroxy-octahydro- 4H-inden-4-one and an unidentified minor product. The synthesis of 5-(2-propenyl)-5β-cholestan-2-ol-3-one was partially completed. The epimeric 5-(2-propenyl)-5β-cholestan-2-ol-3-one. was synthesised. The ene reaction was observed in refluxing toluene giving 2α,5-(1-methylethano)-5α-cholestan-2β-ol-3-one and 3α,5-(methyethano)-5α-cholestan-3β–ol-2-one. The ketone analogue, 5-(2-propenyl )-5α-cholestan-3-one underwent an ene reaction in decalin in a sealed tube at 250°C to give 2α,5-(1-methylethano) -5α-cholestan-3-one.