Peri-and regio-selectivity in cycloaddition reactions of 1-substituted pyridinium-3-oxide

1-methyl- and 1-phenylpyridinium-3-oxides [Ia and Ib] reacted with benzalacetophenone [II] to yield three types of bicyclic adducts. The first proceeded via 2 pi + 4 pi cycloaddition across the 2 6-positions of the pyridine ring to give single regioisomers in favor of endo-6-substituted azabicyclo [3.2.1] octenones [III] and [IV]. The second involved 2 pi + 8 pi, by addition across the C[4]-O, to give the dihydrofuro [2,3-c] pyridine [VII], and the involved C[2]-O to give substituted dihydrofuran V and VI. 1-[4,6-dimethylpyrimidin-2-yl] pyridinium-3-oxide [Ic] reacted with 4-nitrophenylisothiocyanate by addition across the C[2]-O to give the oxazole-2-thione derivative X. Structural assignments were deduced by elemental analysis and spectral evidence

Transformations of 8-azabicyclo [3-2-1] octenones into 4-and 5-methylpyridin-3-ol and indole-tropane derivative

8-[substituted]-2-oxo-8-azabicyclo [3.2.1]-oct-3-ene derivatives Ia and Ib reacted with di-azomethane to give the corresponding two regioisomers of delta 2-pyrazoline derivatives II and III which were transformed directly into 4- and 5-methylpyridin-3-ols on pyrolysis. The synthesized 8-[2-cyanoethyl-8-azabicyclo [3.2.1] octan-6-exocarbonitrile-2-phenylhydrazone VIIa was treated with trifluoromethanesulfonic acid to yield the indole. derivative VIII

Regio- and stereoselectivity in 1,3-dipolar cycloaddition reactions of 1- [phthalazin-3-yl] -3-oxidopyridinium betaine with 2 -1,3-dipolarophiles

Cycloaddition to 1-[phthalazin-3-yl]-3-oxidopyridinium betaine, across the 2, 6-positions of the pyridine ring with 2 pi-electron addends, gave substituted 8-azabicyclo [3.2.1] oct-3-en-2-ones. Structural and configurational assignments of the cycloadducts were deduced from PMR and IR spectral data