Vinyl-pyridines, nucleophilic addition

This preparation illustrates an efficient two-step process for the transformation of a cycloalkenone to the corresponding a-substituted derivative. The first step involves the installation of an a-iodo substituent by a process thought to involve nucleophilic addition of pyridine, iodine capture of the resulting enolate, and pyridine-promoted elimination of pyridine.5 The resulting vinyl iodides are superior to other vinyl halides as participants in a variety of transition-metal catalyzed coupling reactions, illustrated here by the Suzuki coupling with an arylboronic acid. Other coupling partners that... 

The product is a useful intermediate in the synthesis of the analgesic epibatidine. Selective reduction of the non-conjugated double bond is followed by addition of a pyridine nucleophile (a lithium derivative can be prepared from a bromopyridine) to the vinyl sulfone. 

In order to obtain well-defined AB diblock copolymers by anionic polymerization and sequential monomer addition, some crucial conditions must be fulfilled (1) the carbanion formed by the second monomer must be more, or at least equally, stable than the one derived from the first monomer, and (2) the initiation of polymerization of the second monomer by the anion of the first monomer must be higher than the rate of propagation of monomer B. To fulfill these requirements, the monomers used must be added sequentially in the order of increasing electron affinity (e.g., a-methyl styrene (aMeSt) < St butadiene (Bd)< vinyl pyridine < methyl methacrylate (MMA)) and the nucleophilicity of the intermediate macromolecular carbanion A formed should at least match (though... 

Movassaghi and Hill developed a ruthenium-catalyzed cycloisomerization of 3-azadienynes to the corresponding pyridines [11]. The alkynyl imines were produced from a variety of iV-vinyl and iV-aryl amides by amide activation and nucleophilic addition of copper(I) (trimethylsilyl) acetylide sequence reaction. Then by Ru-catalyzed protodesilylation and cycloisomerization, the desired pyridine derivatives were formed selectively in good to excellent yields (Scheme 2.7). For the reaction mechanism, C-silyl metal vinylidene was found to be the key intermediate. 

Tetracyanobutanal acetal (216) (readily obtained from tetracyanoethylene, ethyl vinyl ether, and ethanol) has been reported to be converted into 2-aminopyridine derivative (219) in the presence of pyridine. On the basis of several experiments, the proposed mechanism involves the Michael reaction of (216) via (217) with diene (218), generated by the elimination of hydrogen cyanide and ethanol from (216), followed by double intramolecular nucleophilic additions to the cyano groups. ... 

Vinyl groups a or y to the pyridine nitrogen atom readily undergo Michael additions. Water, alcohols, ammonia, amines and hydrogen cyanide are among the nucleophiles which may be added. For example, 2-vinylpyridine and dimethylamine give the adduct (701 X = NMe2). 

Cyclopenta-fused pyridines 48 have been synthesized through a cascade initiated by intermolecular addition of C radicals to the C = N triple bond in vinylisonitriles. The reaction in Scheme 2.8 shows addition of the nucleophilic alkynyl radical 49 to the carbon end of the isonitrile group in 46 to give vinyl radical 50, which undergoes a... 

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