Synthesis and characterization of metallatranes with phenyl substituents in atrane cage

A new series of mono- and diphenylsubstituted silatranes and boratranes N(CH2CH2O)2(CHR3CR1R2O)MZ (M = Si, Z = CH2Cl, Ctriple bond; length of mdashCPh, H, OMenth, R1, R2, R3 = H, Ph; M = B, Z = nothing, R1, R2, R3 = H, Ph) have been synthesized. Both transalkoxylation and stepwise modification of a preformed metallatrane skeleton were used. The chloromethyl derivatives N(CH2CH2O)2(CHRCHRO)SiCH2Cl (R = H, Ph) react with tert-BuOK under intramolecular cycle expansion to give 1-tert-butoxy-2-carba-3-oxahomosilatranes N(CH2CH2O)(CH2CH2OCH2)(CHRCHRO)SiOtBu (R = H, Ph). The treatment of boratranes N(CH2CH2O)2(CH2CR1R2O)B (R1,R2 = H, Ph) with triflic acid and trimethylsilyl triflate results in the products of electrophilic attack at the nitrogen atom. The molecular structures of four silatranes and one boratrane bearing phenyl groups in the atrane skeleton were determined by the X-ray structure analysis.