4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes: synthesis, structure, and conformational analysis

摘要

4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes RN[CH2Si(Me)(2)](2)O [R = Me (1), i-Pr (2)] were synthesized by two methods which provided good yields up to 84%. Low temperature NMR study of compounds (1) and (2) revealed a frozen ring inversion with the energy barriers of 8.5 and 7.7 kcal/mol at 163 and 143 K, respectively, which is substantially lower than that for their carbon analog, N-methylmorpholine. DFT calculations performed on the example of molecule (1) showed that N-Me-ax conformer to exist in the sofa conformation with the coplanar fragment C-Si-O-Si-C, and its N-Me-eq conformer in a flattened chair conformation.