G. P. Okonnishnikova

Acylation of spiro(1-pyrazoline-3,1′-cyclopropanes) to form 1-acyl-3-(2-chloroethyl)-2-pyrazolines and transformation of bicyclic 2-pyrazolines into 1,4,5,6-tetrahydropyridazines

Strained polycyclic spiro(1-pyrazoline-3,1′-cyclopropanes) react with acetyl or benzoyl chlorides at 0–15 °C regioselectively to give in high yields corresponding 1-acyl-3-(2-chloro-ethyl)-2-pyrazolines. Under the same conditions 6-ethenyl-4,5-diazaspiro[2,4]hept-4-ene gives a mixture of two pyrazolines resulting from the acyl group attack directed at different nitrogen atoms. Bicyclic pyrazolines-2 obtained by acylation of the cycloaddition products of diazocyclopropane with 3,3-disubstituted cyclopropenes transform under the action of hydrogen chloride to 1,4,5,6-tetrahydropyridazines in high yields.

Synthesis and chemical transformations of 2-cyclopropyl-2-diazoacetates

Methyl 2-cyclopropyl-2-diazoacetate was synthesized from acetylcyclopropane in few chemical steps in ∼55% total yield. Its copper or rhodium-catalyzed dediazoniation exclusively proceeds through the intramolecular isomerization of generated cyclopropyl(methoxycarbonyl)carbene to 1-methoxycarbonylcyclobutene, irrespective of the presence or the absence of unsaturated compounds. However, in the presence of acrylates or strained cycloalkenes, this diazo ester is being slowly involved into the 1,3-dipolar cycloaddition, giving cyclopropyl-substituted pyrazolinecarboxylates, which in case of 1-pyrazolines easily lose nitrogen molecule to selectively afford 1-cyclopropylcyclopropanecarboxylate derivatives.

Formation of N-cyclopropylhydrazones by azo coupling of cyclopropyldiazonium with aliphatic CH acids

Decomposition of N-cyclopropyl-N-nitrosourea under the action of K2CO3 or KOH containing 15—20% of H2O at 0—7 °C gives rise to cyclopropyldiazonium, which reacts with some β-diketones, methyl cyanoacetate, or malonodinitrile to form the corresponding cyclopropylhydrazones. The latter compounds are analogous to products of azo coupling and isomerization of aryldiazonium ions with the above-mentioned substrates. These transformations provide the first example of azo coupling of the cyclopropyldiazonium ion in the series of activated aliphatic CH acids.

Reactions of spirocyclopropane-containing 1- and 2-pyrazolines with electrophilic reagents

Hydrochlorination of spiro(1-pyrazoline-3,1′-cyclopropanes) proceeds regioselectively at the azocyclopropane group to form 3-(2-haloethyl)pyrazoline derivatives. If the latter contain a halogen atom in the heterocycle, they are readily converted into (2-haloethyl)pyrazole hydrohalides. Bromination of 3-cyanospiro(2-pyrazoline-5,1′-cyclopropane) withN-bromosuccinimide at 20°C proceeds with retention of the cyclopropane ring to form 3-bromo-3-cyanospiro(1-pyrazoline-5,1′-cyclopropane), which is converted into (2-bromoethyl)cyanopyrazole in ∼60% yield at ∼20°C after 3–4 days.

Unusual formation of hydroperoxides in the reactions of substituted spiro[pyrazolinecyclopropanes]

Abstract3-Cyano- and 3-(alkoxycarbonyl)spiro[2-pyrazoline-5,1’-cyclopropane] and 5-phenylspiro[1-pyrazoline-3,1’-cyclopropane] undergo unusual transformations into 3(5)-substituted 5(3)-(2-hydroperoxyethyl)pyrazoles in the presence of atmospheric oxygen. The conditions for the formation of hydroperoxides (e.g., in oxygen-saturated solutions of spiro[2-pyrazoline-5,1’-cyclopropanes] in CHCl3) and their conversion into (2-hydroxyethyl)pyrazoles or the corresponding nitrates under the action of nitrosating reagents were considered.

Hepta(methoxycarbonyl)cycloheptatriene halo derivatives

A reaction of potassium hepta(methoxycarbonyl)cycloheptatrienide with chlorine and bromine gave high yields of the corresponding chloroand bromohepta(methoxycarbonyl)cycloheptatrienes; the fluoro derivative was obtained by the exchange reaction of the corresponding bromide with silver fluoride. In contrast to the mentioned halides, the iodo derivative has proved unstable. Thermolysis of bromohepta(methoxycarbonyl)cycloheptatriene was studied, as well as its conversion to the azido and methoxy derivatives upon treatment with NaN3 or methanol.

Generation of 1-aryl-3-methoxycarbonylnitrilimines and their reaction with halogen-containing unsaturated compounds

Thermal decomposition of 1-(4-methoxyphenyl)- and 1-(4-fluorophenyl)hepta(methoxycarbonyl)-3a,7a-dihydroindazoles at 135 °C in the presence of allyl or propargyl halides leads to the elimination of hexamethyl benzenehexacarboxylate and the formation of the corresponding pyrazolines or pyrazoles as the products of 1,3-dipolar cycloaddition of 1-aryl-3-methoxycarbonylnitrilimines to the multiple bonds of the substrates used. In the case of vinyl halides, the products of the target reactions are either obtained in low yields or nonexistent, with a side conversions taking place instead. Thus, for example, in the case of 1,1-dichloro-4-methylpenta-1,3-diene, besides hexamethyl benzenehexacarboxylate, 3,5,5-trichloro-2-methylpent-4-en-2-ol and arylchlorohydrazones MeO2CC(Cl)=N-NHAr were unexpectedly isolated as the main products, as well.

Generation and trapping of cyclopropyldiazonium and diazocyclopropane in the nitrosation of cyclopropylamine with alkyl nitrites

Diazocyclopropane and an cyclopropyldiazonium ion, which are highly reactive intermediates, can be generated and trapped by appropriate substrates immediately in the direct nitrosation of cyclopropylamine with alkyl nitrites. Diazocyclopropane is trapped by unsaturated compounds to form the corresponding 1,3-dipolar cycloadducts, while cyclopropyldiazonium reacts with reactive arenes and CH acids (e.g., malononitrile) to give azo compounds. It was shown that both cyclopropyldiazonium and diazocyclopropane in equilibrium can be simultaneously trapped in the presence of equimolar amounts of 2-naphthol and acrylonitrile or methyl methacrylate.

REACTION OF DIAZOALKANES WITH UNSATURATED COMPOUNDS 13.* A NEW METHOD OF PREPARATION AND 1+2- AND 3+2-CYCLOADDITION REACTIONS OF DIAZOPROPYNE

A THF solution of diazopropyne was obtained in 60% yield by the reaction of a 30% aqueous solution of methylamine withN,N′-dinitroso-N,N′-dipropargylterephthalodiamide. The reactions of diazopropyne with methyl acrylate and methyl methacrylate giving various ethynylpyrazolines as well as its CuCl-catalyzed decomposition in the presence of norbornene or norbornadiene yielding ethynylcyclopropanes were studied. The main products of catalytic deazotization of diazopropyne in the absence of unsaturated compounds are isomericE- andZ-hex-3-ene-1,5-diynes resulting from propargylene dimerization.

1,3-Dipolar cycloaddition of diazocyclopropane to strained cycloalkenes and conjugated dienes to give spiro(1-pyrazoline-3,1′-cyclopropanes)

Polycyclic spiro(1-pyrazoline-3,1′-cyclopropanes) were obtained in 32–70 % yields by the reaction of diazocyclopropane generatedin situ with 2-methyltricyclo[3.2.1.02,4]oct-6-ene, spiro[2,4]hepta-4,6-diene dimer, benzvalene, spiro[2,3]hex-1-ene, methyl 1-methylcyclopropene-3-carboxylate, buta-1,3-diene, and 2-methylbuta-1,3-diene.