Methyl vinyl ketone → Hexahydro-1H-quinolizin-2(6H)-one

Participants

Reaction Conditions

Reaction Steps

The compounds of Formula (A) are prepared by acid treatment of the addition product of methyl vinyl ketone and an aminobutanal, pentanal, or hexanal dialkylacetal, such as diethyl acetal. The reaction is performed by first dissolving the appropriate aminoacetal in an appropriate solvent, typically diethyl ether at 0° C., and then adding approximately 1.7 equivalents of methyl vinyl ketone. Typically the reaction is allowed to stir at 0° C. for approximately 2 hours before acidification by addition of, or extraction with, aqueous hydrochloric acid. Typically, the organic layer is removed before heating the aqueous layer to approximately 100° C. for 1 hour. The resulting 7-octahydroindolizinone, 2-octahydro-2H-quinolizinone, or 4-(1-azabicyclo[5.4.0]undecan)ones (A) may be isolated from the reaction mixture by adjusting the pH of the solution to alkaline and extracting with a water immiscible solvent such as ethyl acetate or dichloromethane. The compounds recovered may be used directly in subsequent steps or first purified by silica gel chromatography or vacuum distillation.

Provenance & Evidence