2-Diazonio-1-[(3-methylbut-2-en-1-yl)oxy]ethen-1-olate → 6,6-Dimethyl-3-oxabicyclo[3.1.0]hexan-2-one

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Reaction Steps

A solution of 3-methyl-2-butenyl diazoacetate (980 mg, 6.4 mmoles) in dioxane (15 ml) was added dropwise to a solution of bis[2-butoxy-α-[2-butoxy-5-(1,1-dimethylethyl)phenyl]-5-(1,1-dimethylethyl)-α-[(S)-1-[[2-hydroxyphenyl)methylene]amino]ethyl]benzenemethanolato (2-)]-copper (83 mg, 0.064 mmole) in dioxane (55 ml) at 110°. When the evolution of nitrogen started, the temperature was slowly lowered to 52°-3°. The addition took 5.5 hours, and the evolution at almost theoretical amounts of nitrogen was observed. After the addition was completed, the reaction mixture was stirred at 52°-3° for 2 hours, evaporated to dryness, and distilled under vacuum to afford 6,6-dimethyl-2-oxo-3-oxabicyclo[3.1.0]-hexane enriched with the (1R,5S) isomer (500 mg). The optical rotation of the product was [α]D29 =-53.5° (CHCl3).

Provenance & Evidence