Reaction of dicyanomethylides with 3-(3′,3′-dimethyltriazene-1-yl)- pyridine-4-carboxylic acid. Unexpected preferential formation of pyrido[4,3-a]indolizines
Contrary to theoretical predictions on the basis of a discrete hetaryneintermediate (frontier orbitals, total atomic charges on C-3 and C-4, and activation energies for the concerted process) from the MO calculations, reactions of dicyanomethylides with 3-(3′,3′-dimethyltriazene-1-yl)pyridine-4-carboxylic acid, a formal precursor of 3,4-didehydropyridine, afforded exclusively the pyrido[4,3-a]indolizines
The 1,3-Dipolar Cycloaddition Reactions of Heteroaromatic Dicyanomethylides with Phenylsulfinylethene and Bis(trimethylsilyl)ethyne: Synthesis of 1,2-Unsubstituted 3-Cyanoindolizines
Pyridinium and diazinium dicyanomethylides underwent 1,3-dipolar cycloaddition-extrusion reactions with phenylsulfinylethene, producing the corresponding 3-cyanoindolizines in moderate to good yields. 1,3-Dipolar cycloadditions of these ylides with bis(trimethylsilyl)ethyne gave either the 1,2-bis(trimethylsilyl)-3-cyanoindolizines or the 1-trimethylsilyl-3-cyanoindolizines, or mixtures of these, depending
Cycloaddition reactions of cycloimmonium ylides with triphenylcyclopropene
作者:Kiyoshi Matsumoto、Takane Uchida
DOI:10.1039/p19810000073
日期:——
course of the reaction is discussed qualitatively. The pyrazinium dicyanomethylide (16) with TPP produces the 7-azaindolizine (19), whereas pyridazinium (17) and phthalazinium (18) dicyanomethylides give the primary adducts (20) and (21), respectively. Reaction of pyridinium bis(alkoxycarbonyl)methylides (22) with TPP gives, however, generally poor or no yield of the indolizines.
Nitrogen 14 NMR and Correlations of Oxidation Potentials of Dibenzo[a,d]cycl[2.2.3]azines with the Corresponding HOMOs: Further Evidence for Peripheral Conjugate System
For the first time, (14)N NMR spectra of a novel type of heterocycles, dibenzo[a,d]cycl[2.2.3]azines were described. The chemical shifts are almost independent of substituents at position 2. The correlations of oxidation potentials with HOMO energies of dibenzo[a,d]cycl[2.2.3]azines also offer very good correlation coefficients (r(2)> 0.92) regardless of calculation methods at various levels. Thus, it was concluded that the contribution of the unshared electron pairs of the central nitrogen to the peripheral conjugation in this system is almost negligible.
MATSUMOTO K.; UCHIDA T.; PAQUETTE L. A., SYNTHESIS, 1979, NO 9, 746-747