2-(1-Methyl-1H-indol-3-ylmethylene)-1-aza-bicyclo[2.2.2]octan-3-one:: Acid-catalyzed isomerization of the Z isomer to the E isomer

Crystals of (Z)-2-(1-methyl-1H-indol-3-ylmethylene)-1-aza-bicyclo[2.2.2] octan-3-one (I) were obtained from a condensation reaction of 1-methyl-1H-indole-3-carboxaldehyde with 1-aza-bicyclo[2.2.2] octan-3-one and subsequent crystallization of the product from methanol. The isomeric (E)-2-(1-methyl-1H-indol-3-ylmethylene)-1-aza-bicyclo[2.2.2] octan-3-one hydrochloride (II) was obtained by treating a methanolic solution of I with a 1M solution of hydrogen chloride diethyl ether, followed by crystallization of resultant product from methanol. Crystal data: I, is monoclinic, P2(1), a=5.7440(10), b=11.102(2), c-10.708(2) Angstrom, beta=91.751(10)degrees, and V=682.5(2)Angstrom(3) with Z=2, for D-cal=1.296 mg/m(3) and II, is monoclinic, P2(1)/c, a=8.8510(2), b=17.4990(5), c=20.4300(5) Angstrom, beta=101.3620(12)degrees, V=3102.26(14) with Z=8, for D-cal=1.316 mg/m(3).