Basicity and bulkiness effects of 1,8-diaminonaphthalene, 8-aminoquinoline and their alkylated derivatives on the different efficiencies of η5-C5H5 and η5-C5Me5 ruthenium precatalysts in allylic etherification reactions
作者:Giovanna Brancatelli、Dario Drommi、Giusy Feminò、Maria Saporita、Giovanni Bottari、Felice Faraone
DOI:10.1039/c0nj00338g
日期:——
The different behaviours of Ru(η5-C5H5) and Ru(η5-C5Me5) precatalysts, [Ru(η5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me), in the allylic etherification reaction of cinnamyl chloride using the phenoxide anion as a nucleophile was considered. The N,N ligands are the commercial products 1,8-diaminonaphthalene and 8-aminoquinoline, and their derivatives obtained by alkylation of the amino nitrogen atoms: alkyl substituents that are also bulky chiral C2-symmetric frameworks allow modulation of the basicity and steric demand of the ligands. Some of the precatalysts, [Ru(η5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me), were also synthesized and characterized. The cinnamyl phenyl ether isomers were obtained with very high B/L regioselectivity values, either with Ru(η5-C5H5) or Ru(η5-C5Me5) precatalysts. The highest B/L regioselectivity values achieved with Ru(η5-C5Me5) precatalysts were found with the N,N ligand 1,8-diaminonaphthalene and its derivatives; with Ru(η5-C5H5) precatalysts best B/L values were obtained with ligands derived from 8-aminoquinoline. A correlation between the B/L regioselectivity, and the Ï-donor power and bulkiness of the substituents at the nitrogen atoms of the N,N coordinated ligand was established, but the Ru(η5-C5H5) or Ru(η5-C5Me5) precatalysts followed an opposite trend. It was also found that the low ee values did not depend on the diastereomeric composition of the chiral-at-metal precatalyst [Ru(η5-C5R5)(NCMe)(N,N)]PF6.
考虑了Ru(η^5-C5H5)和Ru(η^5-C5Me5)前催化剂[Ru(η^5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me)在肉桂氯化物的烯丙醇醚化反应中使用酚氧阴离子作为亲核试剂的不同表现。N,N配体是商业产品1,8-二氨基萘和8-氨基喹啉,以及通过烷基化氨基氮原子获得的其衍生物:也具有大型手性C2对称框架的烷基取代基可以调节配体的碱性和空间需求。一些前催化剂[Ru(η^5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me)也被合成和表征。肉桂酚醚异构体获得了非常高的B/L区域选择性值,无论是使用Ru(η^5-C5H5)还是Ru(η^5-C5Me5)前催化剂。与Ru(η^5-C5Me5)前催化剂一起获得的最高B/L区域选择性值是在N,N配体1,8-二氨基萘及其衍生物下找到的;与Ru(η^5-C5H5)前催化剂,最佳B/L值是在源自8-氨基喹啉的配体下获得。建立了B/L区域选择性与N,N配体氮原子上取代基的σ-供体能力和体积之间的相关性,但Ru(η^5-C5H5)或Ru(η^5-C5Me5)前催化剂则呈现相反的趋势。还发现,低的ee值并不依赖于手性金属前催化剂[Ru(η^5-C5R5)(NCMe)(N,N)]PF6的二对映体组成。