Yaşar Dürüst

Reaction of heterocyclic enamines with nitrile oxide and nitrilimine precursors

Alkylidenepyrrolidines 1, 21, 24 and 26 undergo reactions with nitrile oxides and nitrilimines or their precursors to give a range of novel heterocyclic compounds. With alkylidenepyrrolidine ester 1, nitrolic acids give products in which the liberated nitrous acid reacts with the alkylidenepyrrolidine, followed by two cycloadditions to give adducts 3. In contrast, hydroximoyl chlorides give isoxazoles 10, presumably by cycloaddition/elimination. With hydrazonyl chlorides, simple acylation of the alkylidenepyrrolidine occurs to give compounds 17. With sulfonyl alkylidenepyrrolidines 24 and 26, cycloaddition onto the imine tautomer is the preferred pathway, with a stereoselective reaction taking place in the latter case.

Synthesis and stereochemistry of some novel dihydropyrrolo[3,4-c]pyrazoles

Eleven novel dihydropyrrolo[3,4-c]pyrazole derivatives were obtained by the reaction of chiral (1R)-N-(1-phenylethyl)maleimide and C,N-aryl-substituted nitrilimines. The reaction afforded the cycloadducts as a regioisomeric mixture which can be separable in some cases. The structure and stereochemistry of cycloadducts were assigned on the basis of infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), mass and X-ray spectra, optical rotation measurements, and CHN analyses.Graphical Abstract.

An efficient one-pot synthesis of 5-(substituted amino)-1,2,4-thia- and - oxa-diazoles

A general protocol for the synthesis of 5-(substituted amino)-1,2,4-thiadiazoles by the cyclocondensation reaction of amidoximes with N-substituted thioureas in the presence of KF/Al2O3, and of 5-(cyclohexylamino)-1,2,4-oxadiazoles with DCC in the presence of KF/Al2O3 and thiourea, is described. The structures of the new compounds were elucidated by spectroscopic and physical data, and the crystal structure determination by X-ray diffraction of three examples.

Thiophene-Substituted 1,2,4-Oxadiazoles and Oxadiazines

Twenty one new thiophene-substituted 1,2,4-oxadiazol-5(4H)-ones, 1,2,4-oxadiazol-5(4H)-thiones, and 1,2,4-oxadiazin-5(6H)-ones were synthesized by the reaction of thiophene-ring substituted amidoximes with ethyl chloroformate, thiophosgene, and chloroacetylchloride, respectively. Their structure elucidation was performed by means of spectral measurements (IR, NMR, and MS) and physical data.

Microwave-assisted coupling reaction of N-aryl sydnones with 2-nitromethylenethiazolidine: unexpected formation of (Z)-2-(nitro((E)-p-substitutedphenyldiazenyl)methylene)thiazolidines.

Reaction of N-aryl sydnones with 2-nitromethylenethiazolidine straightforwardly gives rise to the formation of (Z)-2-(nitro((E)-p-substitutedphenyldiazenyl)methylene)thiazolidines in xylene and dimethoxyethane under microwave irradiation. A meaningful and plausible mechanism for this transformation is proposed, which anticipates the extrusion of an aceto-lactone-like moiety before a coupling occurs. The structures of all the new compounds were identified on the basis of the data obtained from the NMR, IR, X-ray diffraction spectra, HRMS measurements, and physical characteristics.

Regioselective 1,3-dipolar cycloaddition of phenanthrolinium N-ylides to substituted arylidene oxazolones

The 1,3-dipolar cycloaddition reactions of phenanthrolinium ylides have been investigated. Thus 15 novel aryl substituted spiro[oxazole-4,10′-pyrrolo[1,2-a][1,10] phenanthrolin]-5-ones were prepared in a regioselective manner, by the treatment of phenanthrolinium ylides with (Z)-arylidene oxazolones.

Bis(3-phenyl-1,2,4-thiadiazole-5-thiolato)mercury(II).

The title compound, [Hg(C8H5N2S2)2], has crystallographic C2 symmetry. The Hg-S distance is 2.353 (2) A and the coordination geometry is linear, with an S-Hg-S angle of 179.77 (18) degrees. The exocyclic C-S single-bond distance is 1.749 (6) A, and intramolecular Hg...N distances of 2.857 (4) A exist, as well as secondary Hg...C and S...S contacts.

Synthesis, crystal structure, and in vitro antiprotozoal activity of some 5-phenyl(methyl)sulfonyl-substituted dihydroisoxazoles

Abstract4,5-Dihydroisoxazole derivatives are interesting synthetic targets that exhibit various biological activities, including anti-infective. Taking account of the principle of bioisosterism, a number of 4,5-dihydroisoxazoles carrying a phenyl- (or methyl-)sulfonyl group at position 5 were designed and synthesized by 1,3-dipolar cycloaddition of nitrolic acid-generated nitrile oxides with electron-deficient phenyl (or methyl) vinyl sulfones. The structures of all the cycloadducts were elucidated by means of spectroscopic methods (NMR, MS), X-ray diffraction, and physical characteristics. The in vitro antiprotozoal and cytotoxic activities of these heterocyclic compounds were investigated.Graphical abstract

Synthesis of Some Novel 1,3,4- and 1,2,4-Thiadiazole Derivatives

Synthesis and spectral characterization of novel 1,3,4-thiadiazole derivatives including one organo-mercury compound are described. Their structure elucidation was performed by means of spectroscopic and physical methods (IR, 1H NMR, 13C NMR, MS, X-ray).

Novel benzothiophene 1,1-dioxide deoxygenation path for the microwave-assisted synthesis of substituted benzothiophene-fused pyrrole derivatives.

The reaction of C-(4-substituted-phenyl)-N-(benzoyl)-N-methylglycines with benzo[b]thiophene 1,1-dioxide unexpectedly gave benzothiophene-fused pyrrole derivatives in toluene under microwave irradiation via a cycloaddition and metal-free Pummerer-type sulfone deoxygenation path. In order to obtain the desired sulfone derivatives, the sulfide group underwent oxidation with m-CPBA to afford sulfones. The structures of all the new products were elucidated by spectroscopic/physical methods and, in two cases, by X-ray diffraction.Graphical Abstract