In:
Chemistry – A European Journal, Wiley, Vol. 26, No. 40 ( 2020-07-17), p. 8742-8748
Abstract:
We report the first transition metal catalyst‐ and ligand‐free conjugate addition of lithium tetraorganozincates (R 4 ZnLi 2 ) to nitroolefins. Displaying enhanced nucleophilicity combined with unique chemoselectivity and functional group tolerance, homoleptic aliphatic and aromatic R 4 ZnLi 2 provide access to valuable nitroalkanes in up to 98 % yield under mild conditions (0 °C) and short reaction time (30 min). This is particularly remarkable when employing β‐nitroacrylates and β‐nitroenones, where despite the presence of other electrophilic groups, selective 1,4 addition to the C=C is preferred. Structural and spectroscopic studies confirmed the formation of tetraorganozincate species in solution, the nature of which has been a long debated issue, and allowed to unveil the key role played by donor additives on the aggregation and structure of these reagents. Thus, while chelating N , N , N’,N’ ‐tetramethylethylenediamine (TMEDA) and ( R , R )‐ N , N , N’,N’ ‐tetramethyl‐1,2‐diaminocyclohexane (TMCDA) favour the formation of contacted‐ion pair zincates, macrocyclic Lewis donor 12‐crown‐4 triggers an immediate disproportionation process of Et 4 ZnLi 2 into equimolar amounts of solvent‐separated Et 3 ZnLi and EtLi.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.202001294
Language:
English
Publisher:
Wiley
Publication Date:
2020
detail.hit.zdb_id:
1478547-X
detail.hit.zdb_id:
1231884-X
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