A. Camparini

Photodimerization of N-benzyl-1,4-dihydronicotinamide

Abstract N-benzyl-1,4-dihydronicotinamide dimerized on irradiation with λ=365nm across 2,3 and 5,6 double bonds to give the product I which closed to centro-symmetric cage dimer IV on further irradiation with λ⩽313nm.

BH3 THF reduction of 3-methylisoxazolo [4,5-c]pyridines

Abstract 3-Methylisoxazolo[4,5-c]pyridine 1 on reduction with BH3:THF gave, via the isolable complex 4 , the tetrahydroisoxazolopyridine 5 . The presence of two chlorine atoms at the 4 and 6 positions directed borane attact to the isoxazole ring, yielding the aminoethylpyridine 8 . Both types of reduction were obtained with 6-chloroisoxazolo[4,5-c]pyridine 7 .

Thermal behaviour of 3-phenyl-1,2,4-oxadiazol-5-ylhydrazines

Depending on the substitution on the hydrazine moiety, thermolysis of 3-phenyl-1,2,4-oxadiazol-5-ylhydrazines (1)–(5) gives variable amounts of 1-amino-Δ2-1,2,4-triazolin-5-ones (13) or (17), Δ2- or Δ3-1,2,4-triazolin-5-ones (12), (18), or (19), and the s-triazine (20). A possible mechanism accounting for the products and the effects is discussed. A diradical intermediate and a hydrogen transfer from the reaction medium are suggested on the basis of the effect of benzoyl peroxide on the reaction and on the behaviour of the hydrazines (1)–(4) towards catalytic hydrogenation.

Thermally induced isomerisation of isoxazol-5-ylhydrazines

The thermal isomerisation of isoxazol-5-ylhydrazines (I) led to 1-aminopyrazolin-5-ones (II), 4-aminopyrazolin-5-ones (III), and 1,2,4-triazin-6-ones (IV), in ratios depending on the nature of the substituents and the solvents used. A reaction mechanism involving a bicyclic intermediate, is suggested on the basis of the behaviour of isoxazolyl hydrazines methylated on the hydrazine moiety towards heating. Heating the methylated isoxazolyl-hydrazines (IXg and h) afforded the corresponding azirinecarbohydrazides (XII).

Syntheses and reactivities of 3-methylisoxazolo[4,5-b]pyridines

A synthetic pathway to 3-methylisoxazolo[4,5-b]pyridine and some of its derivatives is described. The determination of methoxydechiorination rates for the 5,7-dichloro-(12) and 5-chloro-derivative (14) showed a noteworthy activation in respect of 2,4-dichioropyridine (22) and 2-chioropyridine (23).