2-Methyltetrahydrofuran → tert-butyl 4-[(E)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)but-3-enyl]-4,9-diazaspiro[5.5]undecane-9-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a mixture of tert-butyl 8-but-3-ynyl-3,8-diazaspiro[5.5]undecane-3-carboxylate (2.41 moles; 750.86 g), zirconocene chloride (240.73 mmoles; 62.08 g), triethylamine (240.73 mmoles; 33.55 mL; 24.36 g), and 2-methyltetrahydrofuran (738 mL), add 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.53 moles; 323.49 g). Heat the mixture to 60° C. and stir overnight. Cool the mixture and pass through a plug of silica eluting with dichloromethane. Concentrate the filtrate under reduced pressure to give the final title compound, tert-butyl 4-[(E)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)but-3-enyl]-4,9-diazaspiro[5.5]undecane-9-carboxylate (1072 g, about 94% purity, 96% yield).

Provenance & Evidence