King reaction

Quinolizinium salts, hydroxytetrahydro-reactions, 2, 549 synthesis, 2, 555, 556 Quinolizinium salts, 1-methyl-synthesis, 2, 552 Quinolizinium salts, 2-methyl-condensation reactions, 2, 539 Ortoleva-King reaction, 2, 540 Quinolizinium salts, 4-methyl-Ortoleva-King reaction, 2, 540 Quinolizinium salts, l-oxo-l,2,3,4-tetrahydro-reactions, 2, 549 synthesis, 2, 555... 

Both 2-methyl- and 4-methyl-quinolizinium salts undergo the Ortoleva-King reaction (Scheme 37) to produce the expected pyridinium salts and these with p-dialkylamino-nitrosobenzenes were found to give nitrones (46) (65JPR(27)306). 

G. R. Ames, H. M. Blackmore, and T. A. King., Reaction of sugars with halomethyl ethers,... 

Ortoleva-King reaction refers to the direct reaction of an active methyl or methylene compound 1 with iodine and pyridine to generate the corresponding pyridinium iodide 2 along with an equivalent of pyridine hydroiodide salt 3. 

The mechanism of the Ortoleva-King reaction is proposed as following Deprotonation of methylene compound 1 by one equivalent of pyridine affords its anion 4 along with pyridinium ion. A second equivalent of pyridine was activated by iodine to generate iodopyridinium intermediate 5. 

After a simple filtration or sometimes without isolating the pyridinium salt product, the Ortoleva-King reaction may be followed by further chemical transformation, giving rise to a variety of synthetically useful compounds. 

The phenylacylpyridinium salt, obtained from the Ortoleva-King reaction, could undergo facile hydrolysis to give rise to the corresponding carboxylic acid. Pratt et al. reported an efficient synthesis of 6-carboxydehydroabietic acid 11 from methyl acetyldehydroabietate 9 via a one-pot procedure. The... 

Research by Berson et al. showed that 2-pyridone 15 could be accessed via the basic hydrolysis of pyridinium diiodide 13, which was obtained from the Ortoleva-King reaction of picolinium iodide 12 and used without isolation. The reaction proceeded even at room temperature, therefore providing an extremely mild way to access 2-pyridones. 

The Ortoleva-King reaction also found application in the following sequence where a methyl or methylene compound such as 2-methylthiazole 16 was converted to the corresponding aldehyde 197 The preparation of pyridinium salt 17 via Ortoleva-King reaction of 16 was followed by nitrone formation to give 18, whose hydrolysis led to desired aldehyde 19. This mild sequence is especially suitable for the preparation of sensitive aldehydes, which might be difficult to obtain using other synthetic approaches. 

With well-positioned substituents, the product from the Ortoleva-King reaction may be followed by readily ring closures to yield a variety of heterocycles. Case in point was made by an elegant synthesis of 2-pyridyl-pyrrocoline 22 reported by Krdhnke et al First, picoline salt 21 was prepared from the Ortoleva-King reaction of acylpyridine 20 and picoline. Upon treatment of saturated sodium bicarbonate 21 underwent rapid cyclization to give rise to pyrrocoline 22 in excellent yield. 

Kiliani reagent 16, 138 Kindler s. Willgerodt King reaction 16, 777 Kishner s. Wolff Knoevenagel condensation 7, 781... 

The King reaction, in which quaternary pyridinium salts are prepared from iodine, pyridine, and a compound containing a reactive methyl group has already been mentioned. It was seen that the picolines are not sufficiently reactive to take part in the reaction, but that 1,2- and 1,4-dimethylpyri-dinium salts do react ( ). 179). 

---