Diisopropylamine → HCID 20146597, compound

Participants

Reaction Conditions

Reaction Steps

n-Butyllithium (23.8 ml of a 2.60 M solution in hexane) was added slowly to an ice-cold solution of 8.7 ml of N,N-diisopropylamine in 30 ml of anhydrous tetrahydrofuran. The solution was stirred at 0° C. for 15 minutes and treated with 10.8 ml of hexamethylphosporamide; it was then stirred at 0° C. for 15 minutes and cooled to -78° C. A solution of 5 g of 1,5,6,7-tetrahydro-1,6,6-trimethyl-4H-indazol-4-one in 150 ml of anhydrous tetrahydrofuran was added dropwise, followed by the dropwise addition of 8.9 ml of ethyl formate. The reaction was allowed to warm to room temperature and was stirred for 20 hours and 150 ml of water was added and the mixture was extracted with dichloromethane. The aqueous layer was acidified with aqueous hydrochloric acid and extracted exhaustively with dichloromethane. The combined extracts were dried over magnesium sulfate and concentrated in vacuo to provide a dark oil which crystallized upon standing. Flash chromatography of this material (10% acetone in dichloromethane) on silica gel provided product as light yellow crystals. Recrystallization from hexane/toluene gave 4,5,6,7-tetrahydro-1,6,6-trimethyl-4-oxo-1 H-indazole-5-carboxaldehyde melting at about 131°-132° C.

Provenance & Evidence