Addition reactions of heterocycles. VI. Reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with nitrilimines

Addition reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with C-acetyl-N-phenylnitrilimine, have been investigated. 1,2-Dimethylpyrrole gives three different types of adducts: i.e. bis-cycloadducts (Vc) and (VIc), spirocycloadduct (IX), and non cyclic bis-adduct (XII). On the other hand, 1-methyl-2-carbomethoxypyrrole gives the bis-cycloadduct (VIb) only. Compound XII arises probably through a double 1,3-addition reaction, whereas the formation of cycloadducts Vc, VIc, and IX depends on the substituents present at C2 of the pyrrole ring and consequentially on the intermediary occurence of mono-cycloadduct (IIIc), its methylenic tautomer VII, VIc, and XL The behaviour of …

Cycloadditions in the pyrrole series

Addition reactions of heterocycles—IV

Abstract The reactivity of indole derivatives towards nitrilimines has been studied. Substituents at positions 1, 2 and 3 of the indole ring greatly affect the course of the reaction. 1,3-Dipolar cycloaddition products (3a,8a,dihydropyrazole-[3,4-b]-indole derivatives) and non-cyclic addition products (3-indolyl derivatives) were obtained depending on these substituents. The structures reported were assigned on the basis of satisfactory analytical, spectroscopic and chemical data.

Heterocyclic rearrangements. Phenylhydrazones andN-methyl-N-phenylhydrazones of 3-acylisoxazoles

The reaction of 3-benzoyl-5-phenylisoxazole (4) and 3-acetyl-5-methylisoxazole (5) with phenylhydrazine and N-methyl-N-phenylhydrazine has been investigated and the reactivity of (E)- and (Z)-phenylhydrazones and N-methyl-N-phenylhydrazones has been studied.

Mononuclear heterocyclic rearrangements. Part 12. Rearrangement of 1,2,4-oxadiazoles into indazoles

The first example of a mononuclear heterocyclic rearrangement involving an XYZ = CCN side-chain sequence is reported. The 3-(o-aminophenyl)-, and 3-(o-methylaminophenyl)-5-methyl-1,2,4-oxadiazoles (3a,b) gave a thermally induced rearrangement into 3-acylaminoindazoles (4a,b). On the other hand, the 3-(o-acetylaminophenyl)-5-methyl-1,2,4-oxadiazole (3c) produced a base induced rearrangement into 3-acetylaminoindazole (4a).

Mononuclear heterocyclic rearrangements. Part III. Rearrangement of theP-methoxyphenylhydrazone and them-nitrophenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole in dioxane/water in thepS+range 3.8-11.5

The rates of the mononuclear heterocyclic rearrangement of the p-methoxyphenylhydrazone (Ib) and the m-nitrophenylhydrazone (1c) of 3-benzoyl-5-phenyl-1,2,4-oxadiazole have been measured in the range of pS+ 3.8–11.5 (solvent: dioxane/water 1:1, v:v) and compared with those of the unsubstituted phenylhydrazone (Ia). The obtained results show that in the base-catalyzed range, electron-repelling as well as electron-withdrawing substituents accelerate the rearrangement rates.

Mononuclear isoheterocyclic rearrangements. Note I. Interconversion of 3-benzoylamino-5-methyl-1,2,4-oxadiazole and 3-acetylamino-5-phenyl-1,2,4-oxadiazole

The first example of mononuclear isoheterocyclic rearrangement is reported. The 3-benzoylamino-5-methyl-1,2,4-oxadiazole (5) furnishes through a reversible process (slowly at room temperature in methanol, acetone or dioxane, fast in DMSO or in methanol in the presence of strong bases) a mixture of 5 and 3-acethylamino-5-phenyl-1,2,4-oxadiazole (6). The equilibrium process can be achieved also by heating 5 at 181° and the same reaction mixture can be obtained using 6 as the starting material. 3-Trichloroacetylamino-5-methyl-1,2,4-oxadiazole (7) was unaffected by similar treatment. The results obtained are discussed.

Addition reactions of heterocycles. VII. Pyrrole andC-Acetyl-N-phenylnitrilimine

The addition reaction of C-acetyl-N-phenylnitrilimine to pyrrole has been investigated. The products obtained show that the reaction proceeds via two distinct pathways. The 1,3-addition reaction leads to the non-cyclic-adduct III, whereas the 1,3-cycloaddition reaction gives a mixture of regioisomeric Δ2-pyrroline IV and V, and Δ1 -pyrroline VI and VII mono-cycloadducts. These latter compounds cannot be isolated because they undergo a further 1,3-cycloaddition reaction leading to the N-substituted bis-adducts X and XI, and to the bis-adduets XII and XIII. The stereochemical assignment for X, XI, XII and XIII is provided by nmr data which suggest also that in X and XI the rotation around the…

Heterocyclic rearrangements.N,N-diphenylhydrazones, oximes andO-methyloximes of 3-benzoyl-5-phenyl-1,2,4-oxadiazole

The behaviour of (E)- and (Z)-N,N-diphenylhydrazones and O-Methyloximes of 3-benzoyl-5-phenyl-1,2,4-oxadiazole has been studied. When refluxed in benzene, or in dioxane-water (1:1), the (Z)-N,N-diphenylhydrazone 8Z gave the indazole 11 or the substituted semicarbazide 12, respectively. The O-methyloxime 14Z did not give any rearrangement. A criticism of the oximation reaction of 3-benzoyl-5-phenyl-1,2,4-oxadiazole is also reported.

Mononuclear heterocyclic rearrangements—vi

Publisher Summary This chapter discusses the mononuclear heterocyclic rearrangements. The chapter discusses the ring conversion of type 1→2 characterized by nucleophilic attack from a Z atom on a sp 2 -nitrogen atom with displacement of an atom. On this basis, the known ring conversions are tabulated. Taking into account the reactivities observed in the rearrangements, results are presented for 1,2,4-oxadiazole, isoxazole, and 1,2,5-oxadiazole. The sequence involving an oxime group in the side chain is discussed. The chapter presents several attempts for inducing rearrangements in which the reaction center of the starting ring is an atom other than nitrogen. Rearrangement of arylhydrazones …