norbornane‐2,5‐dione. These ligands were applied to various catalytic reactions such as asymmetric deprotonation, asymmetric bromine‐lithium exchange, and enantioselective addition of aryl‐ and allkylithium reagents to aromatic aldimines.
Intramolecular Methylacridan-Methylacridinium Complexes with a Phenanthrene-4,5-diyl or Related Skeleton: Geometry-Property Relationships in Isolable CH Bridged Carbocations
Bridging the gap: Snapshots of 1,6‐H‐shift precursors indicate that a narrower CH⋅⋅⋅C+ separation (D in the ORTEP diagram) in the title complexes induces faster degenerate rearrangement of 1+. A contact distance of less than 2.7 Å is necessary to realize the organic three‐center two‐electron bond of [CHC]+, as indicated by extrapolation of the X‐ray data.
The present invention is a photochromic material formed of a biimidazole compound represented by general formula (1-1):
(where, R
4
and R
5
respectively and independently represent a halogen atom or alkyl group, R
1
to R
3
and R
6
to R
8
respectively and independently represent a hydrogen atom, halogen atom, alkyl group, fluoroalkyl group, hydroxyl group, alkoxyl group, amino group, alkylamino group, carbonyl group, alkylcarbonyl group, nitro group, cyano group or aryl group, Ar
1
to Ar
4
respectively and independently represent a substituted or unsubstituted aryl group, R
4
may form a condensed, substituted or unsubstituted aryl ring with R
3
, and R
5
may form a condensed, substituted or unsubstituted aryl ring with R
6
).
Asymmetric bromine–lithium exchange: on the importance of both the diamine ligand and the organolithium reagent
作者:Jézabel Praz、Julien Graff、Léo Egger、Laure Guénée、Simon Wagschal、E. Peter Kündig、Alexandre Alexakis
DOI:10.1039/c5cc06548h
日期:——
The asymmetric bromine–lithium exchange on a series of prochiral biphenyls was investigated.
对一系列具有手性前体的联苯进行了不对称溴-锂交换的研究。
Catalytic Asymmetric Bromine-Lithium Exchange: A New Tool to Build Axial Chirality
作者:Quentin Perron、Alexandre Alexakis
DOI:10.1002/adsc.201000517
日期:2010.10.4
We present here the first catalytic desymmetrization of the 2,2′,6,6′-tetrabromobiphenyl 1 and analogues, by a bromine-lithiumexchange catalyzed by either diamines or diether derivatives (0.5 equiv.), yielding axiallychiral compounds in high yield (up to 89%) and high enantioselectivity (up to 82%).