N-(2,6-Dimethyl-4-oxopyridin-1 -yl)pyridinium salts (4), new reagents for the regiospecific synthesis of 4substituted pyridines, give moderate to high yields of 4-alkyl-and 4-aryl-pyridines (8)-(10) on reaction with Grignard reagents. The scope and limitations of the reaction, which proceeds via 1,4-dihydro-intermediates (5)-(7), are explored. No 2-substituted pyridines were detected. Some reactions with organolithium compounds are also described.
reported herein gave spectral data in full accord with the assigned structures. New compounds which were sufficiently stable to allow for full characterization gave satisfactory elemental analyses and/or molecular weight measurements (high resolution mass spectrometry). 17) G. H. Posner, D. J. Brunelle, L. Sinoway, Synthesis 1974, 662. (81 In the case of [(6a)-(6d)], silyl enol ether formation was highly regioselective [exclusive or nearly exclusive formation of (70)-(7d)].-When lithium 2.2.6.6-tetramethylpiperidide was used as a base in the place of lithium diisopropylamide, (10) was formed as the major product.191 For studies related to the thermal rearrangement of methylene(viny1)cyclopropane systems, see also W E.
Synthesen 4‐substituierter Pyridine (3) dürften immer breites Interesse finden. Im Pyridinium‐Ion (1) sind die Positionen 2 und 6 sterisch abgeschirmt; es reagiert deshalb an der aktivierten Position 4 mit C‐, N‐ und S‐Nucleophilen in hoher Ausbeute zu (2), das sich leicht in (3) und (4) zerlegen läßt oder in diese Produkte zerfällt.magnified image
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