Prepn: GB 772212 (1957 to Ruhrchemie); Korte, Stiasni, Ann. 656, 140 (1962); Feichtinger, Linden, Chem. Ind. (London) 1965, 1938. Toxicity study: Tauberger, Arch. Exp. Pathol. Pharmakol. 232, 227 (1957).