Design, Synthesis, and Application of a C2 Symmetric Chiral Ligand for Enantioselective Conjugate Addition of Organolithium to α,β-Unsaturated Aldimine
摘要:
A C-2 symmetric chiral diether ligand, (1R,2R)-1,2-dimethoxy-1,2-diphenylethane was designed and synthesized on the basis of the concept of an asymmetric oxygen atom. Mediated by the chiral diether, high enantioselectivities were achieved in conjugate addition of organolithiums to naphthaldehyde imine and cyclic and acyclic alpha,beta-unsaturated aldimines. The absolute configuration of the product is predictable by the model.
A reaction mode of imines derived from naphthalene-1-carbaldehyde and acyclic alpha,beta-unsaturated aldehydes with organolitium reagents was dependent on the characteristic nature of a substituent on the imine nitrogen atom. An imine having an electron-withdrawing aryl group on the nitrogen atom behaves as a 1,2-directing imine toward organolithium reagents. In contrast, an imine bearing an alkyl
The 1,4-addition reaction of organolithiumreagents with 2,6-bis(tert-butyl)-4-methoxyphenyl naphthalenecarboxylates gave regioselectively substituted dihydronaphthalenecarboxylates in high yields. Successive treatment of the esters with organolithiums in THF, lithium triethylborohydride, methyl iodide, and finally sodium borohydride in methanol, provided regio- and stereoselectively the corresponding
Asymmetric additions to chiral naphthalenes. III. The synthesis of (+)-trans-1,2-disubstituted-1,2-dihydronaphthalenes
作者:A. I. Meyers、Bruce A. Barner
DOI:10.1021/jo00351a034
日期:1986.1
1,2- vs. 1,4-addition of nucleophilic organometallics to nonracemic 2-(1-naphthyl)- and 2-cinnamyl-1,3-oxazolidines
作者:Lendon N. Pridgen、Mohamed K. Mokhallalati、Ming Jung Wu
DOI:10.1021/jo00030a035
日期:1992.2
We herein report our results where the addition of organomagnesium reagents to 2-(1-naphthyl)- and 2-cinnamyl-1,3-oxazolidines occurred consistently in a 1,4-conjugate manner, while lithium, cerium, and copper organometallic reagents added in a 1,2-fashion. The 1,4-conjugate addition pathway was primarily exploited by using (4R)-2-(1-naphthyl)-4-phenyl-1,3-oxazolidine (4) as a substrate to obtain, after NaBH4 reduction of the intermediate aldehyde, trans-disubstituted 1,2-dihydronaphthalenes with enantiomeric excesses of 93-94%. The amino alcohol products resulting from 1,2-addition were oxidatively cleaved to afford enantiomeric enriched (R)-alpha-(1-naphthyl)alkylamines 6a and 6b in > 99% ee.
Reductive generation of aldehyde metal enolate from ketene. A one-flask process to 1,1,2- and 1,2,2-trisubstituted dihydronaphthalenes from 1- and 2-naphthalenecarboxylates