Synthesis of nitrogen-containing dispiroheterocycles (1) using nitrilimines

A novel series of 1,2,4,5,10,11,13,14-octaazadispiro[5.2.5.2]hexadeca-2,12-dienes 4a-k were synthesized by the reaction of 1,4-cyclohexanedione methylhydrazone 3 with appropriate nitrilimines 2 . The microanalysis and the spectral data of the synthesized compounds are in full agreement with their molecular structure


Introduction
In recent years, attention has been increasing regarding the synthesis of spiroheterocyclic compounds which exhibit various biological activities, 1-8 pharmaceutical 9,10 and antitumor properties. 11,12Nitrilimines are well explored dipoles and their reactions for the construction of heterocyclic systems are known to proceed via 1,3-dipolar cycloaddition with multiple bonds, cyclocondensation with nucleophilic substrates and 1,3-electrophilic addition with nucleophiles.Examples of these modes of reactions were recently reviewed by Ferwanah et al. 13 for the reactions of hydrazones and oximes with nitrilimines and nitrile oxides.The synthesis of different spiroheterocycles I-III was recently reported using nitrilimines and cycloalkanone hydrazones or oximes [14][15][16][17] (Figure 1).As part of our program aimed at developing new biologically active compounds, we report here the synthesis of the hitherto unknown dispiroheterocyclic compounds 4a-k from the reaction between different nitrilimines 2 and 1,4-cyclohexanedione methyl hydrazone 3.

Spectral data analysis
The structures of compounds 4a-k were established based on the basis of their elemental analysis and spectroscopical data.Physical properties, molecular ion peaks and elemental analysis for these triazinones are presented in the experimental section.The electron impact (EI) mass spectra displayed the correct molecular ions in accordance with the suggested structures.Their IR spectra showed absorption bands in the region 3280-3250 cm -1 and 1660-1640 cm -1 assignable to NH and carbonyl group, respectively.Their 1 H NMR spectra revealed, besides aromatic protons at 8.5-7.1 ppm and singlet signal at 3.2-3.0ppm assigned to NCH 3 protons and D 2 O-exchangeble singlet signal in the region 5.7-5.6 ppm assignable to the ring NH proton.The detailed 1 H NMR data is shown in the experimental section.Their 13 C NMR spectra showed all the signals corresponding to the proposed structures, especially C-6 and C-9 (spiro carbons) were found to resonate at about 75-70 ppm.This is similar to reported values of spiro carbons flanked by two nitrogen atoms in sixmembered heterocycles, 14,22 which provide strong evidence in support of the structures 4a-k.The complete 13 C NMR data are presented in experimental section.

Biological activity
Most of the newly synthesized compounds 4a-k were tested for their antibacterial and antifungal activity in vitro against bacterial strains such as Escherichia coli, Staphylococcus aureus, Klebsiella spp, Proteus spp, Pseudomonas and Aspergillus flavus, Candida albicans as fungi, employing the nutrient agar disc diffusion method 23 at (1-10 mg/ml) in dimethyl formamide (DMF) by measuring the inhibition zone in mm.It is interesting to note that these

Experimental Section
General Procedures.All melting points were determined on an A. Krüss Melting Point Meter equipped with a digital thermometer and are uncorrected.The IR spectra were measured as potassium bromide pellets using a Satellite 3000 Mid infrared spectrophotometer.The 1 H NMR and 13 C NMR spectra were recorded on a Bruker AM 300 MHz spectrometer at room temperature in DMSO-d 6 solution using tetramethylsilane (TMS) as internal reference.Chemical shifts were recorded as δ values in parts per millions (ppm) downfield from internal TMS.Electron impact (EI) mass spectra were run on Shimadzu GCMS-QP1000 EX spectrometer at 70 eV.Elemental analysis was performed at Cairo University, Egypt.The hydrazonoyl halides 1ak [18][19][20][21][22] and 1,4-cyclohexanedione methylhydrazone 3 24 were prepared according to literature procedures.Tetrahydrofuran (THF) and triethylamine were purchased from Avocado Research Chemicals, England, and used without further purification.

Reaction of nitrilimines 2 with 1,4-cyclohexanedione methylhydrazones 3
Triethylamine (0.05 mol, 7 ml) in tetrahydrofuran (10 ml) was added dropwise to stirred mixture of a hydrazone 3 (0.02 mol) and the appropriate hydrazonoyl halides 1a-k (0.01 mol) in tetrahydrofuran (70 ml) at -5-0 o C. The reaction temperature was allowed to rise slowly to ambient temperature and stirring was continued for 4-6 hours.The precipitated triethylammonium salt was filtered off and the solvent was then evaporated.The residue was washed with water (100 ml) and in few cases the gummy products were triturated with ethanol (10 ml).The crude solid product was collected and recrystallized from ethanol to give the desired compounds.The following compounds were synthesized using this method: