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The direct amination of pyridine with sodium amide can take place in liquid ammonia or an aprotic solvent such as xylene is commonly used. Following the addition elimination mechanism first a nucleophilic NH 2 − is added while a hydride (H −) is leaving. The reaction formally is a nucleophilic substitution of hydrogen S N H.
Correspondingly pyridine is more prone to nucleophilic substitution, as evidenced by the ease of metalation by strong organometallic bases. [84] [85] The reactivity of pyridine can be distinguished for three chemical groups. With electrophiles, electrophilic substitution takes place where pyridine
This reaction mechanism is supported by the observation that addition of pyridine to the reaction leads to inversion. The reasoning behind this finding is that pyridine reacts with the intermediate sulfite replacing chlorine. The dislodged chlorine has to resort to nucleophilic attack from the rear as in a regular nucleophilic substitution. [3]
Nucleophilic aromatic substitution is not limited to arenes, however; the reaction takes place even more readily with heteroarenes. Pyridines are especially reactive when substituted in the aromatic ortho position or aromatic para position because then the negative charge is effectively delocalized at the nitrogen position.
Synthesis of nucleosides involves the coupling of a nucleophilic, heterocyclic base with an electrophilic sugar. The silyl-Hilbert-Johnson (or Vorbrüggen) reaction, which employs silylated heterocyclic bases and electrophilic sugar derivatives in the presence of a Lewis acid, is the most common method for forming nucleosides in this manner.
Nucleophilic acyl substitution mechanism. Other types of nucleophilic substitution include, nucleophilic acyl substitution, and nucleophilic aromatic substitution. Acyl substitution occurs when a nucleophile attacks a carbon that is doubly bonded to one oxygen and singly bonded to another oxygen (can be N or S or a halogen), called an acyl ...
This white solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe 2 substituent. Because of its basicity, DMAP is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides , the Baylis-Hillman reaction , hydrosilylations , tritylation, the Steglich ...
A typical reaction diphenylacetylene is obtained by the coupling of iodobenzene with CuC 2 C 6 H 5 in hot pyridine: [1] Unlike the Sonogashira coupling, the Castro–Stephens coupling can produce heterocyclic compounds when a nucleophilic group is ortho to the aryl halide, although this typically requires use of dimethylformamide (DMF) as ...