Pyridinium salts reaction with Grignard reagents

A review of the literature prior to 1953 on reactions of pyridinium, quinolinium, and isoquinolinium salts is available (31). The reactions will be described here only briefly. The initial observation was that of Freund et al. (32-37), who found that treatment of various derivatives of hydra-stinine (15) with Grignard reagents yielded addition products, such as 16. 

This reaction was first reported by Breckpot in 1923. It is the synthesis of )0-lactam via the cyclization of esters of /3-amino acids with Grignard reagent and is known as the Breckpot -lactam synthesis. This reaction has been modified to form )0-lactam by the treatment of )0-amino acid with Mukaiyama s reagent, or the /3-amino ester with /V-methyl pyridinium salt." ... 

Reactions of highly electron-rich organometalate salts (organocuprates, orga-noborates, Grignard reagents, etc.) and metal hydrides (trialkyltin hydride, triethylsilane, borohydrides, etc.) with cyano-substituted olefins, enones, ketones, carbocations, pyridinium cations, etc. are conventionally formulated as nucleophilic addition reactions. We illustrate the utility of donor/acceptor association and electron-transfer below. 

Amuilations of pyridinium- and quinolinium-salts however have not been reported so far. From the addition reactions of C-nucIeophiles like Grignard, organozinc and organotin reagents to pyridinium- and quinolinium-salts have been reported to be valuable methods for the construction of substituted dihydropyridine [4a-4d] and dihydroquinoline-derivatives [4d-4e] results of our studies in the field of benzothiopyrylium-salts [5] we concluded that the sequential intermolecular 1,2-addition/intramolecular 1,4-addition of 4-silyloxyquinolinium-salts 1 with 2-silyloxy-l,3-butadienes 2 might be useful for the diastereoselective preparation of annulated quinolones 3. 

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