Pratt Lawrence M, Mogali Sudha, Glinton Kevin
Department of Chemistry, Fisk University, 1000 17th Avenue North, Nashville, Tennessee 37208, USA.
J Org Chem. 2003 Aug 22;68(17):6484-8. doi: 10.1021/jo034498+.
DFT calculations were performed to determine the effects of ethereal solvents on the aggregation state of lithium dialkylaminoborohydrides (LABs). The calculations included dimerization energies in the gas phase, with continuum solvation only, microsolvation with coordinating ethereal ligands, and a combination of the microsolvation and continuum models. The continuum model alone overestimates the stability of the dimers, apparently due to the lack of steric effects from the coordinating ethereal ligands. The use of the combined microsolvation and continuum solvation models predicts lithium dimethylaminoborohydride to be a mixture of monomer and dimer in THF, and more sterically hindered lithium aminoborohydrides to exist primarily as monomers. The kinetics of amination of 1-chlorodecane by lithium dimethylaminoborohydride showed no detectable change in reaction rate with time, suggesting that the LAB reagent may exist primarily as a monomer in THF.
进行密度泛函理论（DFT）计算以确定醚类溶剂对二烷基氨基硼氢化锂（LABs）聚集态的影响。计算内容包括仅采用连续溶剂化模型时在气相中的二聚能、采用配位醚类配体的微溶剂化模型以及微溶剂化模型与连续溶剂化模型相结合的情况。单独的连续溶剂化模型高估了二聚体的稳定性，这显然是由于缺乏配位醚类配体的空间效应。微溶剂化模型与连续溶剂化模型相结合的方法预测，在四氢呋喃（THF）中，二甲基氨基硼氢化锂是单体和二聚体的混合物，而空间位阻更大的氨基硼氢化锂主要以单体形式存在。二甲基氨基硼氢化锂对1 - 氯癸烷进行胺化反应的动力学研究表明，反应速率随时间没有可检测到的变化，这表明LAB试剂在THF中可能主要以单体形式存在。
