Reactions of (Et2NCH2CH2NEt2)·H2SiCl2with Selected Diorganometallic Reagents of Magnesium and Lithium†

Addition of the THF-insoluble di-Grignard reagent from 2,2′-dibromo-4,4′-tert-butylbiphenyl (1) to a solution of [(teeda)·H2SiCl2] in CH2Cl2/THF produced 2,7-di-tert-butyl-9H-9-silafluorene (3) in isolated, recrystallized yields of <20%. The related soluble dilithio reagent from bis(2-bromo-4-methylphenyl)methylamine (2) formed in Et2O, when reacted with [(teeda)·H2SiCl2] in CH2Cl2/Et2O, gave similar yields of 5,10-dihydro-2,5,8-trimethylphenazasiline (4). In the absence of CH2Cl2 the major product produced from 1 was the spirocycle 2,2′,7,7′-tetra-tert-butyl-9,9′-spirobi[9H-9-silafluorene] both in a solvent-free form (5′) and as an ethanol solvate (5), both of which were crystallographically characterized. The spirocycle 2,2′,5,5′,8,8′-hexamethyl-5,10-dihydro-10,10-spirobiphenazasiline (6) was formed from the reaction of the dilithio reagent of 2 in the absence of CH2Cl2.