Solution Structures of Lithium Enolates of Cyclopentanone, Cyclohexanone, Acetophenones, and Benzyl Ketones. Triple Ions and Higher Lithiate Complexes
Solution Structures of Lithium Enolates of Cyclopentanone, Cyclohexanone, Acetophenones, and Benzyl Ketones. Triple Ions and Higher Lithiate Complexes
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DOI：
10.1021/ja903479p
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发表时间：
2009-08-19
影响因子：
15
通讯作者：
Reich, Hans J.
中科院分区：
文献类型：
--
作者：
Kolonko, Kristopher J.;Biddle, Margaret M.;Reich, Hans J.
低温（-110 ~ -150℃）下的多核核磁共振波谱研究表明，对氟酚酸锂以及环己酮、环戊酮和4-氟苯乙酮的烯醇化锂在THF/Et2O和THF/Et2O-HMPA中具有四聚体结构。1,3-二-（4-氟苯基）-2-丙烷（5F-Li）烯酸锂的Z和E异构体表现出发散行为。Z异构体完全是二聚体。纯乙醚，多为二聚体，THF/ether比例为3:2，其中可以检测到少量单体。TMTAN和P， MDTA将Z-5F-Li转化为单体胺配合物，HMPA将其部分转化为m，部分转化为锂离子（RO）(2)Li-和（RO）(3)Li2-。通过在烯酸锂中以1:1的比例加入烯酸磷（使用p4 - but碱），形成三离子（RO）(2)Li(-)P4H(+)，或2:1的比例形成高离子（RO）(3)Li2- (P4H(+))(2))（四离子），制备了表征较好的锂酸盐溶液。在3:2 THF/Et2O溶液中，5F-Li的E异构体也是二聚体，但在PMDTA和HMPA作用下都不能很好地转化为单体。与Z-5F-Li相反，即使在过量HMPA存在下，E异构体在乙醚中也是四聚体。从而表征了5F的两种异构体的六种不同的烯酸酯结构：四聚体、二聚体、cip单体、sip单体、三离子和四离子。
Multinuclear NMR spectroscopic studies at low temperature (-110 to -150 degrees C) revealed that lithium p-fluorophenolate and the lithium enolates of cyclohexanone, cyclopentanone and 4-fluoroacetophenone have tetrameric structures in THF/Et2O and THF/Et2O-HMPA by study of the effects of the addition of HMPA. The Z and E isomers of the lithium enolate of 1,3-bis-(4-fluorophenyl)-2-propanone (5F-Li) show divergent behavior. The Z isomer is completely dimeric in. pure diethyl ether, and mostly dimeric in 3:2 THF/ether, where monomer could be detected in small amounts. TMTAN and P, MDTA convert Z-5F-Li to a monomeric amine complex, and HMPA converts it partially to m, and partially to lithiate species (RO)(2)Li- and (RO)(3)Li2-. Better characterized solutions of these lithiates were prepared by addition of phosphazenium enolates (using P4-Bu-t base) to the lithium enolate in 1:1 ratio to form triple ion (RO)(2)Li(-)P4H(+), or 2:1 ratio to form the higher lithiate (RO)(3)Li2- (P4H(+))(2)) (quadruple ions). The E isomer of 5F-Li is also dimeric in 3:2 THF/Et2O solution, but is not delectably converted to monomer either by PMDTA or HMPA. In contrast to Z-5F-Li, the E isomer is tetrameric in diethyl ether even in the presence of excess HMPA. Thus for the two isomers of 5F six different enolate structures were characterized: tetramer, dimer, CIP-monomer, SIP-monomer, triple ion, and quadruple ion.