Gademann, Karl; Ernst, Martin; Hoyer, Daniel; Seebach, Dieter Angewandte Chemie - International Edition, 1999, vol. 38, # 9 p. 1223 - 1226 doi: 10.1002/(SICI)1521-3773(19990503)38:9<1223::AID-ANIE1223>3.0.CO;2-A