Grignard reagents picolyl, reactions with

The reactions of pyridyl and picolyl metallic derivatives with organic reagents are of great synthetic value. Since the courses taken are, more often than not, normal, no attempt will be made to do more than substantially exemplify these uses and to note some of the infrequent irregularities. It can be said that almost always the yields realized in reactions using the Grignard reagents are inferior to those obtained with lithium, potassium or sodium compounds. 

Pyridine-carboxylic acids have been prepared by the reaction of the 3-pyridyl Grignard reagent 36a and of 2- and 3-pyridyl lithium with carbon dioxide. Nicotinic acid isotopically labelled in the carboxyl group has been obtained in this way . The reaction is especially useful for preparing pyridine-acetic acids and has been applied to 2-2t t and 4-picolyl lithium i. Under conditions where phenyl lithium adds to the azomethine linkage of 4-picoline, 2-phenylpyridine-4-acetic acid i is produced. 2,6-Lutidine gave 6-methylpyridine-2-acetic acid, but the reaction failed with 2-methyl-6-phenoxypyridine . ... 

The 3-pyridyl Grignard reagent has been alkenylated by reaction with allyl halides and the 2-picolyl Grignard reagent homologated with alkyl halides and to-diethoxyalkyl halidesi . Of much greater importance has been the use of picolyl lithium, potassium and sodium compounds in reactions with alkyl and aralkyl halides. 

Pyridyl and picolyl metallic derivatives have frequently been used to prepare carbinols by reaction with aldehydes and ketones. Those of aldehydes have been recorded with the 2-630a, 535, 609 3- 36 and 4-pyridyl34 Grignard reagents, with the double reagent from 2,6-dibromopyridine630 and with lithium derivatives of 2,4-di- and 2,4,6-trimethylpyridine (reaction occurring... 

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