Ylidic polyfunctionalized compounds with a diazinium skeleton

For the first time in the cycloimmonium ylide series we have obtained unsaturated styryl carbanion monosubstituted ylides. These ylides, phthalazinium-and 4-methylpyrimidinium-ylides, have polyfunctionalized character: ylide and alkene. In this paper we have exploited only the ylidic character. The ylides 3 and 4 have been proven to have 1,3-dipole characters ( 3a and 4a ), respectively. Thus, the ylides function as 1,3-dipoles in 3+2 dipolar cycloaddition reactions with various dipolarophiles (such as DMAD, NPM). The structure of all the other compounds (salts and cycloadducts) has been proven through elemental and spectral (IR, NMR) analysis. The in vitro biological activity of the newly obtained phthalazine and pyrimidine compounds was also tested. Some of them have proved to have a remarkable activity against different microorganisms (germs and fungus). Correlation of the structure-biological activity has been studied.


Introduction
The chemistry of cycloimmonium ylides has been widely discussed. 1,2,3The research has focused especially of the ylides of type I. Few studies have been done concerning the ylides II and III.(Scheme 1)

Scheme 1
In the early 70s Acheson and Foxton 4 assumed, for the first time in the diazine series, the existence of ylides with unsaturated carbanion.(Scheme2) Since then no other research has been done in the field of diazinium ylides with unsaturated carbanion although this is a convenient way to acces polyfunctionalized compounds with a ylidic skeleton.

Scheme 2
The emphasis of this work was, on one hand, to get ylides with a new type of unsaturated carbanion (analogous with III) and, on the other hand, to get polyfunctionalized compounds with a ylidic skeleton.Another goal was to test the biological activity of the new compounds.

Results and Discussion
In first instance we tried to get phthalazinium-(3) and pyrimidinium-(4) ylides with unsaturated carbanion, using an adaptation of the Krönke 5 salts method (Scheme 3).Thus, the reactions of phtalazine and 4-methylpyrimidine with cinnamyl bromide yield to the salts 1 and 2, respectively.The structures were characterised by elemental and spectral analysis.The dehydrohalogenation of 1 and 2 with 40% aqueous potassium carbonate lead (according to the TLC) to a mixture of two compounds with a structure impossible to be determined through Because of the unsatisfactory on the elemental and spectral analysis, in order to elucidate the structure of ylides 3 and 4 (but also in order to get new azabicycles compounds) we underwent chemical proves.Thus, we treated ylides 3 and 4, generated in situ, with different dipolarophiles such as DMAD and N-phenylmaleimide (NPM), Schema 5.If the ylides have a 3a respectively 4a structures (having in view that they could accept the canonical structures 3b and 4b), they should function as 1,3-dipoles giving 3+2 dipolar cycloaddition reactions.If the ylides have a 3c respectively 4c structure, they should function as 1,5-dipoles giving 5+2 dipolar cycloaddition reactions.Experimentally we have found that styryl ylides 3 and 4, in reaction with DMAD or/and NPM, give 3+2 cycloadditions reactions.This means that the ylidic structures 3a respectively 4a are the real one.
As it can be seen in Scheme 5 in reaction with DMAD we got the 3+2 azabicyclic compounds 5 and 6.In the case of NPM the reaction took place only with phthalazinium ylide leading to the 3+2 cycloadduct 7 while pyrimidinium ylide did not react (the last one being less reactive 6 ).
Pyrrolo-diazine cycloadducts 5 and 6: In the IR spectra the signals corresponding to CO ester groups appear at 1750-1700 cm -1 .The signals are very strong and broaded with 2 maximum: 1740 cm -1 (ν C=O,Me2 ) and 1725 cm -1 (ν C=O,Me1 ) in 5 and respectively at 1735 cm -1 (ν C=O,Me5 ) and 1720 cm -1 (ν C=O,Me6 ) in 6.In the 1 H NMR spectra the most important evidence for pyrrolophthalazine 5 and pyrrolopyrimidine 6 structures are the following : -the rings are aromatized because of the missing signals corresponding to saturated protons; -the ethenyl protons appear at chemical shifts and with coupling constants in accordance with the proposed structures, in trans.In compound 5 proton H 11 appear at δ=4.30-4.25 ppm (d, J=13.4 Hz) and H 12 at δ=4.86-4.82ppm (d, J=13.4 Hz).In comound 6 proton H 8 appear at δ=4.30-4.10ppm (d, J=13.0 Hz) and H 9 at δ=5.00-4.80ppm (d, J=13.0 Hz); -the Me ester groups appear as non equivalent because of the different magnetic vicinity.Thus, in compound 5 the group Me 1 appear at 3.71 ppm (s) and Me 2 at 3.81 ppm (s), while in compound 6 the group Me 5 appear at 3.30 ppm (s) and Me 6 at 3.80 ppm (s). 13C NMR spectra of compound 5 confirm also the structure: 175.9 ppm (C 1a , ester with conjugation), 174.1 ppm (C 2a , ester with conjugation), 52.73 ppm (Me 2 ester), 51.14 ppm (Me 1 ester).These data confirm, as well as the 1 H-NMR , the different magnetic vicinity of the two ester groups.The ethenyl carbons appear at 127.35 ppm (C 12 )  The in vitro antimicrobial and antifungical activity of the newly obtained phtalazine and 4methylpyrimidine compounds was tested having in view that our previous study has proven a certain biological activity in this respect to related compounds. 7,8,9he test was performed using the diffusimetric method 10 with rustlessteel cylinders based on the diffusion of the tested substances on the gelose surface (for bacteria) and Sabouard environment (for fungus Candida albicans).The cylinders were maintained 24 h at thermostat, at 34 0 C for bacteria and at 37 0 C for Candida.The tested substances were previously disolved in DMFA 5% (v/v).A witness solvent sample has been done.The inhibition diameter zone, in mm, of development of microbial strain was measured.It is considered active 11 a compound for which the difference between the inhibition diameter zone of compound and witness is up to 2 mm (3-4 mm moderate active and up to 5 very active).The results are listed in Table 1.The comparative analysis of the obtained data (Table 1) leads to the following conclusions concerning the relation between structure and biological activity: -both type of salts, 1 (from phthalazine) and 2(from pyrimidine), have a remarkable non selective activity against Gram positive and Gram negative germs; -cycloadducts 5, 6 and 7 have a moderate activity against germs; -either the salts and cycloadducts are less active or inactive against fungus Candida; -we decide to test and the mixture ylide-dimer 3 and 4. The mixture ylide-dimer 4 from pyrimidine prove to be very, very active having a remarkable non selective activity against germs and also against fungus Candida; -if we compare the compounds from the two series, phthalazine and

Conclusions
For the first time in the cycloimmonium ylides we have obtained styryl carbanionmonosubstituted ylides.These ylides, phthalazinium-and 4-methylpyrimidiniumylides, have polyfunctionalized character: ylide and alkene.In this paper we exploited only the ylidic character.
Five new diazine compounds (1,2,5,6,7) were synthesized.The structure of these compounds (salts and cycloadducts) has been proven through elemental and spectral analysis.The structure of the ylides 3 and 4 has been proven to be of type 3a respectively 4a through chemical ways (however, we classify these compounds as hazardous).
The in vitro biological activity of the newly obtained phthalazine and pyrimidine compounds was tested.Some of them proved to have a remarkable activity against different microorganisms (germs and fungus).Correlation of the structure-biological activity has been studied.

Experimental Section
General Procedures.
1 H-and 13 C-NMR spectra were run on a Varian Gemeni 200 MHz and Bruker 80 MHz spectrometer and were recorded in ppm downfield from an internal standard, SiMe 4 in CDCl 3 .The coupling constants are given in Hz.The IR spectra were recorded with a SPECORD-71 spectrometer in KBr.The melting points are uncorrected.
General procedure to obtain diazinium ylides.Salt 1 or 2 (1 mmol) was dissolved in 50 ml water and treated with an aqueous solution of K 2 CO 3 40% when the ylide was obtained.The ylide was filtered to vacuum, washed with a great amount of water and dried to vacuum.

Phthalazinium cinnamyl methylide (3). CAUTION: hazardous compound! According to
General Procedure using compound General procedure to obtain 3+2 cycloadducts.The cycloimmonium salt (10 mmol) and DMAD or NPM (10 mmol) were suspended in 50 ml of benzene.The mixture was heated on a steam bath and triethylamine (10 mmol, dissolved in 30 ml benzene) was then added dropwise in 3 h.The resulting mixture was filtered hot, to eliminate triethylamine bromhydrate.The clear solution was evaporated on a steam bath.The crude products recrystallized from an appropriate solvent for compounds 5 and 7, and for compound 6 we done and flash chromatography on silica using dichloromethane-methanol 98:2.

5 Cycloadduct 7 :
Scheme 5 pyrimidine, we notice that the pyrimidine compounds are more active.