A mixture consisting of 16.6 g. of veratraldehyde, 12.5 g. of o-fluorobenzaldehyde, 8 g. of potassium cyanide, and 100 ml of 65% ethanol is reacted as described in Example 20, yielding 12.5 g. of 3,4-dimethoxy-2'-fluorobenzoin, m.p. 126°-128° C. A 5.8 g. portion of the benzoin derivative is converted to its methanesulfonate ester by the procedure of Example 20, giving 6.7 g. of the ester melting at 111°-113° C. 2.58 g. of the methanesulfonate ester, 0.91 g. of hexahydro-2H-1,3-diazepin-2-thione, and 55 ml. of acetone are mixed and left at room temperature for three days. 7 ml. of 2 N ethanolic hydrogen chloride are added, yielding 2.2 g. of the title compound, melting at 192°-194° C.
