40381-28-0Relevant academic research and scientific papers
Synthesis of nitrogen-containing heterocycles using exo- and endo-selective radical cyclizations onto enamides
Taniguchi, Tsuyoshi,Yonei, Daigo,Sasaki, Masamichi,Tamura, Osamu,Ishibashi, Hiroyuki
, p. 2634 - 2641 (2008/09/19)
The effect of positional change of the carbonyl group of enamides on Bu3SnH-mediated alkyl radical cyclization leading to five-, six-, seven-, and eight-membered nitrogen-containing heterocycles was examined. A 5-exo cyclization is generally preferred over a 6-endo ring closure in systems having an alkyl radical center on the enamide-acyl side chain, whereas enamides having an alkyl radical center opposite to the acyl side chain predominantly gave 6-endo cyclization products. These results suggest that the exo or endo selectivity of radical cyclization onto the alkenic bond of enamides can be controlled by positional change of the carbonyl group. For an understanding of these selectivities, heat of formation for each transition state was calculated. 6-endo-Selective radical cyclization was applied to the radical cascade, enabling a concise synthesis of a cylindricine skeleton. A 7- or 8-endo alkyl radical cyclization, however, predominated over a corresponding 6- or 7-exo ring closure regardless of the positional change of the carbonyl group of enamides.
A Versatile New Synthesis of Quinolines and Related Fused Pyridines. Part 12. A General Synthesis of 2-Chloropyridines and 2-Pyridons
Meth-Cohn, Otto,Westwood, Keith T.
, p. 1173 - 1182 (2007/10/02)
The Vilsmeier formylation of tertiary and secondary enamides leads to 2-pyridons and 2-chloropyridines, respectively.The reaction appears to be quite general allowing substitution in the 1-, 3-, 5-, or 6-position or combinations of these.The major limitation arises with enamides which are unsymmetrically substituted on the double bond with alkyl groups, when mixtures can result.Attempts to introduce a 4-substituent by a variation of the Vilsmeier reagent had limited success.
