Stereochemistry of the reaction of pyridinium ylides with ?,?-unsaturated nitriles

Multicomponent Reactions of Carbonyl Compounds and Derivatives of Cyanoacetic Acid: Synthesis of Carbo- and Heterocycles

“…14,15 To this end, a multicomponent re- . [153][154][155][156][157][158][159] Ylides 207, containing a ketone fragment, were also utilized in the multicomponent synthesis of pyridines. The reaction of ylides 207 with aldehydes and cyanothioacetamide stereoselectively generated 2,3-trans-3,4-trans-1,2,3,4-tetrahydropyridines 208 (X = S), 153,[160][161][162][163] whereas a similar reaction of ylides 207, aldehydes, and the dimer of malononitrile gave tetrahydropyridines 208 [X = C(CN) 2 ], containing the dicyanomethylide fragment in the 6-position of the tetrahydropyridinium ring (Scheme 57).…”

A new route for the synthesis of 5,6-dihydropyridin-2(1H)-ones, 2-pyridones and (4-hydroxy-2-oxopiperid-3-yl)pyridinium chlorides by intramolecular cyclization of N-3-oxoalkylchloroacetamide derivatives

“…Reactions of pyridinium ylides leading to formation of a variety of heterocyclic compounds are well known. [8][9][10][11][12] Most of the pyridinium ylide heterocyclizations investigated proceed via an intermolecular Michael addition followed by cyclization of the intermediate into a heterocycle. The intramolecular cyclization of pyridinium ylides is also known, 13 but its application for the synthesis of heterocycles is not widespread.…”

“…The elimination of pyridinium hydrochloride from pyridinium salts such as intermediate 7 has already been described. 12,14 5,6-Dihydropyridin-2(1H)-ones are widely employed in the synthesis of alkaloids and aza sugars and possess significant biological activity. [15][16][17][18] However, there are some restrictions on their synthesis such as inaccessibility of the starting reagents, low applicability of the preparation methods and difficult reaction conditions.…”

N-3-oxoalkylamides and- thioamides in the synthesis of heterocyclic compounds 5. Synthesis of 1-(4-hydroxy-2-oxo-3-piperidyl)-pyridinium chlorides and 2-pyridones from pyridinium derivatives of N-3-oxoalkylchloroacetamides

“…Fission of pyridine hydrochloride from pyridinium salts analogous to compound (VI) is well known [9,10]. In its turn an increase in the acidity of position 6 of the heterocycle assists the isomerization of the intermediately formed dihydropyridin-2(1H)-one (V) into 1-(2-oxo-l,2,3,4-tetrahydro-3-pyridyl)pyridinium chloride (VI).…”