Universität zu Köln

Grote, Vanessa, Neudoerfl, Joerg-Martin and Goldfuss, Bernd (2019). Enantiopure Methyl- and Phenyllithium: Mixed (Carb-)Anionic Anisyl Fencholate-Aggregates. Organometallics, 38 (4). S. 771 - 780. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6041

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Abstract

Methyl- and phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li-3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 angstrom(2), over n-Bu: 2.6S angstrom(2) (previous work) to Ph: 2.79 angstrom(2)). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometries. These computed aggregate formation energies point to preferences for 3:1 over 2:2 aggregates, as it is also apparent from experimental aggregate formations, confirmed by X-ray crystal analyses. In close analogy to the X-ray crystal structures, the computed Li3 surfaces increase with increasing steric demand of the carbanions. The chiral, mixed (carb-)anionic RLi-fencholate aggregates hence adapt to different carbanion sized and arise not only with small (Me) or primary carbanions (n-Bu) but even with the larger secondary phenyl anion.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Grote, Vanessa UNSPECIFIED UNSPECIFIED UNSPECIFIED Neudoerfl, Joerg-Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED Goldfuss, Bernd UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-156324
DOI:	10.1021/acs.organomet.8b00724
Journal or Publication Title:	Organometallics
Volume:	38
Number:	4
Page Range:	S. 771 - 780
Date:	2019
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-6041
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language N-BUTYLLITHIUM; ASYMMETRIC ADDITION; ORGANOMETALLIC REAGENTS; CRYSTAL-STRUCTURES; ENANTIOSELECTIVE ADDITION; ORGANOLITHIUM REAGENTS; LITHIUM AMIDE; COMPLEXES; REACTIVITY; NUCLEOPHILICITY Multiple languages Chemistry, Inorganic & Nuclear; Chemistry, Organic Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15632