Hydrochloric Acid → (4AS,5aS)-1-(pyrazin-2-yl)-4,4a,5,5a-tetrahydro-1H-cyclopropa[4,5]cyclopenta[1,2-c]pyrazole-3-carboxylic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a solution of (1S,5R)-bicyclo[3.1.0]hexan-2-one (52.9 g, 539 mmol) and diethyl oxalate (0.073 L, 539 mmol) in absolute ethanol (0.9 L) (not denatured with methanol) was added a THF solution of potassium tert-butoxide (1.0 M, 0.539 L, 539 mmol) over 15 min (maintaining the temperature below 43° C.). The resulting yellow solution was stirred at 40° C. for 3.5 h. 2-Hydrazinylpyrazine (59.4 g, 539 mmol) was added followed by a 6.0 M aqueous solution of hydrogen chloride (0.270 L, 1618 mmol). The reaction was stirred at 50° C. for 1.5 h. The mixture was poured into ice-water (5 L). A precipitate appeared immediately. After sitting for 30 minutes in an ice bath, the solid was collected by filtration, rinsed with water (5×1 L); and dried to give the title compound (106 g) as an off-white solid 1H NMR. LCMS m/z=271.2 [M+H]+; 1H NMR (400 MHz, CDCl3) δ 0.47 (td, J=4.7, 3.3 Hz, 1H), 1.27 (td, J=8.0, 4.9 Hz, 1H), 1.41 (t, J=7.1 Hz, 3H), 2.26-2.32 (m, 1H), 2.77-2.82 (m, 1H), 2.88 (dd, J=16.7, 1.4 Hz, 1H), 2.99 (dd, J=16.6, 6.4 Hz, 1H), 4.40 (q, J=7.1 Hz, 2H), 8.41 (dd, J=2.5, 1.5 Hz, 1H), 8.52 (d, J=2.5 Hz, 1H), 9.40 (d, J=1.5 Hz, 1H).

Herkunft & Nachweise