Methanesulfonic Acid → Methanesulfonic Acid

Participants

Reaction Steps

In step c, scheme 8, cleavage of the acetal and reductive cyclization of 29 leads to piperazinone 5A. This conversion is performed either in one step using an acid, e.g., trifluoroacetic acid or methanesulfonic acid, and a reducing agent such as sodium borohydride or triethylsilane, in solvents such as dichloromethane, 1,4-dioxane, tetrahydrofuran, water, or mixtures thereof. Alternatively, the reaction may be performed in two steps, by first forming a 3,4-dihydro-1H-pyrazin-2-one intermediate in the presence of an acid, e.g., trifluoroacetic acid or methanesulfonic acid, in a solvent such as water or dichloromethane, and subsequent catalytic hydrogenation at pressures between 1 bar and 10 bar, using a suitable catalyst, e.g., palladium on activated charcoal, in solvents such as methanol, ethanol, ethyl acetate, or mixtures thereof, at temperatures between 0° C. and 50° C.

Provenance & Evidence