In:
Chemistry – A European Journal, Wiley, Vol. 21, No. 41 ( 2015-10-05), p. 14410-14420
Abstract:
Generally considered kinetic intermediates in addition reactions of alkyllithiums to pyridine, 1‐lithio‐2‐alkyl‐1,2‐dihydropyridines have been rarely isolated or characterized. This study develops their “isolated” chemistry. By a unique stoichiometric (that is, 1:1, alkyllithium/pyridine ratios) synthetic approach using tridentate donors we show it is possible to stabilize and hence crystallize monomeric complexes where alkyl is tert ‐butyl. Theoretical calculations probing the donor‐free parent tert ‐butyl species reveal 12 energetically similar stereoisomers in two distinct cyclotrimeric (LiN) 3 conformations. NMR spectroscopy studies (including DOSY spectra) and thermal volatility analysis compare new sec ‐butyl and iso ‐butyl isomers showing the former is a hexane soluble efficient hydrolithiation agent converting benzophenone to lithium diphenylmethoxide. Emphasizing the criticalness of stoichiometry, reaction of n BuLi/Me 6 TREN with two equivalents of pyridine results in non‐alkylated 1‐lithio‐1,4‐dihydropyridine⋅Me 6 TREN and 2‐ n ‐butylpyridine, implying mechanistically the kinetic 1,2‐ n‐ butyl intermediate hydrolithiates the second pyridine.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.201501880
Language:
English
Publisher:
Wiley
Publication Date:
2015
detail.hit.zdb_id:
1478547-X
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