Hasan Tashtoush

Selective monodeoxygenation of quinoxaline-amino acid and ester dioxides

Trimethyl phosphite selectively removes the N-1-oxygen in N-(3-methyl-2-quinoxaloyl) L-α-amino ester-1,4-dioxides, whereas it removes the N-4-oxygen in the corresponding series of dioxides lacking the C3-Me. This selectivity reversal reflects the relative strength of the intrahydrogen-bridging to the N-1-oxygen. The monoxides having the favourable N-oxygen are not reduced to the quinoxalines, implying that the reagent requires doubling of the N-oxide function for deoxygenation. However, alkaline sodium dithionite removes the N-1-oxygen in both series of the amino acid-dioxides, as well as in the parent quinoxaline-2-carboxylic acid-dioxides, a result that contradicts the report stating removal of the N-4-oxygen. The N-oxygenated quinoxalinium ion (me 145 or 159) prevails in the MS of the 4-oxides, but it is not observed (<1%) for the isomeric 1-oxides. 1H NMR, 13C NMR and UV spectral data also offer diagnostic criteria for differentiation between the isomeric 1- and 4-oxides. Aryl-heteryl “interaction” (as revealed by 1H NMR, though not by 13C NMR in the aromatic amino ester dioxides) is not manifested in the corresponding monoxides.

The reaction of acylium salts with dialkylcyanamides

Abstract Aliphatic and aromatic acid chlorides react with dialkylcyanamides in the presence of Lewis acid at low temperature. The reaction proceeds via a stepwise mechanism to afford 1,3,5-oxadiazinium salt in good yields.

Dual behavior of monothiocarbohydrazones in the cyclization with diethyl acetylene dicarboxylate (DEAD): synthesis of substituted 1,3-thiazolidin-4-ones

Condensed 4-thiazolidinones have attracted the attention of organic chemists and pharmacologists due to the biological significance associated with the thiazolidinone nucleus. On the other hand, the synthesis of spiro compounds has always been a challenge and attraction due to their pharmacological activities. 4-Thiazolidinones are embedded in the structures of various synthetic pharmaceuticals displaying a broad spectrum of biological activities (1), including antimicrobial (2), antifungal (3), antimalarial (4), antiviral (5), antibacterial (5), antioxidant (6), anti-HIV (7),

1H and 13C NMR Spectroscopy of Substituted Tris‐1,3,4‐oxadiazoles

1,3,5‐Tris(5‐substituted‐1,3,4‐oxadiazol‐2‐yl)benzenes were prepared by the dehydration of the corresponding hydrazides. The structures of these compounds were elucidated by IR, 1H and 13C NMR spectroscopy.

A novel synthesis of quinone-immonium dyes

Abstract A new method was invoked to synthesize the colored quinoneimmonium cations from the reactions of DMSO with aromatic amines. The novel feature about this method is the use of DMSO as the methylating agent with a lewis acid such as TiCl 4 as a catalyst. This reduced the number of steps traditionally used to prepare these dyes from aromatic amines.

Effect of Ethanol and Acetonitrile Containing Some Aryl-Substituted Bis-1,3,5-Oxadiazinium Salts on the Corrosion of Aluminum

Abstract The chemical and electrochemical behavior of aluminum has been studied in ethanol— and acetonitrile—water mixtures at 15°C using the weight-loss method and the potentiostatic polarization technique. Also, the effect of some aryl-substituted bis-1,3,5-oxadiazinium salts on the corrosion of aluminum in acetonitrile was studied. Acetonitrile and ethanol act as interface inhibitors, whereas oxadiazinium salts with hexachloroantimonate counter anions were found to stimulate the dissolution of aluminum. The effects of the substituent of the aromatic moiety of the oxadiazinium salts and the counter anions on the corrosion of aluminum have also been studied.

Unusual product from the acid-catalyzed one-pot, multicomponent reaction of thiocarbohydrazide, aldehydes, and phenacyl bromides

ABSTRACT A one-pot, three-component protocol for the synthesis of novel five-membered thiazole ring bonded to two hydrazone motifs is described. The acid-catalyzed reaction of one equivalent of thiocarbohydrazide, two equivalents of aromatic aldehydes, and one equivalent of phenacyl bromides afforded the five-membered thiazole ring. The reactions proceed with novel chemoselectivity. Similar reported protocols have always afforded 1,3,4-thiadiazines. GRAPHICAL ABSTRACT

A Notable Antimutagenicity of Two Nonmutagenic Novel Oxadiazoles in Salmonella Mutagenicity Assay

The mutagenic activity of two newly synthesized oxadiazoles: 1,3‐bis(5‐benzylthio‐1,3,4‐oxadiazol‐2‐yl) benzene (M1) and 1,4‐bis(5‐benzylthio‐1,3,4‐oxadiazol‐2‐yl) benzene (M2) was studied in Salmonella typhimurium strains TA97, TA100, TA102 and TA1537 in the presence and absence of S9mix. The antimutagenicity of M1 and M2 against H2O2, sodium azide (SA) and 4‐nitro‐o‐phenylene diamine (NPD) using the tester strains TA102, TA100 and TA97, respectively, was also investigated. The two compounds were found to be nonmutagenic using the four tester strains. However, they showed high mutagenic repression activity against hydrogen peroxide (95% and 97% for M1 and M2, respectively, at a concentration of 335 µg/plate). Moderate mutagenic repression against NPD (58% and 55% for M1 and M2, respectively, at a concentration of 167.5 µg/plate) and low mutagenic repression against SA (21% and 33% for M1 and M2 respectively, at a concentration of 335 µg/plate) was detected. The obtained results are very encouraging to test the above mentioned compounds as anticarcinogens.