Silaheterocyclen. XXVII: Substituenteneffekte zur Steuerung des Cycloadditionsverhaltens von Silaethenen

The silence Cl 2 Si=C(Ph)CH 2 Bu t (2) is formed by the reaction of 1,1,1-trichloro-2-phenyl-1-silaprop-2-ene (1) with LiBu t in n-pentane in the temperature range from -15 to 0 o C. The reaction initially leads to the corresponding α-lithio adduct A (addition of LiBu t to the vinyl group of 1); subsequent LiCl elimination yields 2 as an intermediate. 2 can be trapped by Me 3 SiOMe (3) and dienes which add across the Si=C bond. In the absence of trapping agents but in the presence of the Lewis base NEt 3 the mixture 1/LiBu t reacts to give the disilacyclobutane 4