tert-butyl cyclobutanecarboxylate

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 21.65 ml (54.12 mmol) of a 2.5 M solution of n-butyllithium in hexane were added dropwise to a solution, cooled to from −20° C. to −30° C., of 7.6 ml (54.12 mmol) of diisopropylamine in 30 ml of abs. THF. After the addition had ended, the mixture was stirred at from −20° C. to −30° C. for another 30 min. The mixture was then cooled to −78° C., and a solution of 6.2 g (39.7 mmol) of tert-butyl cyclobutanecarboxylate in 10 ml of abs. THF was added dropwise at this temperature. After 4 h at −78° C., a solution of 7.9 g (36.1 mmol) of 3-bromo-4-chlorobenzaldehyde in 10 ml of abs. THF was then added. The reaction mixture was slowly warmed to RT overnight, saturated aqueous ammonium chloride solution was then added and the mixture was extracted with ethyl acetate. The organic phase was dried over magnesium sulphate and concentrated under reduced pressure. The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 50:1→10:1). This gave 7.77 g of the target compound (56% of theory). After the addition After 4 h at −78° C. The reaction mixture was slowly warmed to RT overnight the mixture was extracted with ethyl acetate The organic phase was dried over magnesium sulphate concentrated under reduced pressure The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 50:1→10:1)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Under argon, 99 μl (0.78 mmol) of boron trifluoride/diethyl ether complex were added to 5.2 g (52.3 mmol) of cyclobutanecarboxylic acid in 100 ml of THF. A little at a time, 13.7 g (62.75 mmol) of tert-butyl 2,2,2-trichloroethaneimidoate were then added, and the mixture was subsequently stirred at room temperature overnight. 5 g of sodium bicarbonate were then added, and the reaction mixture was stirred for 15 min. After filtration, the solution was concentrated to dryness under reduced pressure. The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 4:1). This gave 5.2 g (64% of theory) of the title compound as a yellow oil. the reaction mixture was stirred for 15 min After filtration the solution was concentrated to dryness under reduced pressure The crude product was purified by chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 4:1)