Microwave-Assisted Dehydrosulfurization: An Efficient, Solvent-Free Synthesis of 5-(1-Adamantyl)-2-arylamino-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles

Synthesis, Antimicrobial, and Anti-Proliferative Activities of Novel 4-(Adamantan-1-yl)-1-arylidene-3-thiosemicarbazides, 4-Arylmethyl N'-(Adamantan-1-yl)piperidine-1-carbothioimidates, and Related Derivatives

The reaction of 4-(adamantan-1-yl)-3-thiosemicarbazide 3 with various aromatic aldehydes yielded the corresponding thiosemicarbazones 4a–g. 1-Adamantyl isothiocyanate 2 was reacted with 1-methylpiperazine or piperidine to yield the corresponding N-(adamantan-1-yl)carbothioamides 5 and 6, respectively. The latter was reacted with benzyl or substituted benzyl bromides to yield the S-arylmethyl derivatives 7a–c. Attempted cyclization of 1,3-bis(adamantan-1-yl)thiourea 8 with chloroacetic acid via prolonged heating to the corresponding thiazolidin-4-one 9 resulted in desulfurization of 8 to yield its urea analogue 10. The thiazolidin-4-one 9 and its 5-arylidene derivatives 11a,b were obtained via microwave-assisted synthesis. The in vitro antimicrobial activity of the synthesized compounds was evaluated against a panel of Gram-positive and Gram-negative bacteria and yeast-like pathogenic fungus Candida albicans. Compounds 7a–c displayed marked broad spectrum antibacterial activities (minimal inhibitory concentration (MIC), 0.5–32 μg/mL) and compounds 4a and 4g showed good activity against Candida albicans. Nine representative compounds were evaluated for anti-proliferative activity towards three human tumor cell lines. Compounds 7a–c displayed significant generalized anti-proliferative activity against all the tested cell lines with IC₅₀ < 10 μM.

Crystal structure of 6-(4-chlorophenyl)-3-(thiophen-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazole, C13H7ClN4S2

C13H7ClN4S2, monoclinic, P21/c (no. 14), a = 10.2342 (9) Å, b = 11.9953(10) Å, c = 12.0980(9) Å, β = 116.283(6)°, V = 1331.6(2) Å3, Z = 4, R gt (F) = 0.0573, wR ref (F 2 ) = 0.1675, T = 100 K.

Crystal structure of 6-(2-fluorophenyl)-3-phenyl-[1,2,4]-triazolo[3,4-b][1,3,4]thiadiazole, C15H9FN4S

C15H9FN4S, orthorhombic, Pna21 (no. 33), a = 18.9361(2) Å, b = 11.5248(1) Å, c = 6.0142(1) Å, V = 1312.52(3) Å3, Z = 4, R gt (F) = 0.0263, wR ref (F 2 ) = 0.0706, T = 100 K.

3-(1-Adamant-yl)-4-amino-1-(2-benzoyl-1-phenyl-eth-yl)-1H-1,2,4-triazol-5(4H)-thione

In the title compound, C(27)H(30)N(4)OS, the 3-(adamantan-1-yl)-4-amino-1H-1,2,4-triazole-5(4H)-thione unit and the O atom are each disordered over two sets of sites with refined site-occupancies of 0.7630 (13) and 0.2370 (13). The 1,2,4-triazole ring of the major component forms dihedral angles of 62.61 (17) and 61.93 (16)° with the benzene rings, while that of the minor component makes corresponding angles of 86.3 (4) and 79.1 (4)°. The dihedral angle between the benzene rings is 39.21 (16)°. The mol-ecular structure is stabilized by an intra-molecular C-H⋯N hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked into inversion dimers by pairs of N-H⋯S hydrogen bonds.

Synthesis and antimicrobial activity of N'-heteroarylidene-1-adamantylcarbohydrazides and (±)-2-(1-adamantyl)-4-acetyl-5-[5-(4-substituted phenyl-3-isoxazolyl)]-1,3,4-oxadiazolines

The reaction of adamantane-1-carbohydrazide (1) with heterocyclic aldehydes, namely 5-(4-chlorophenyl)isoxazole-3-carboxaldehyde (2a), 5-(4-methylphenyl)isoxazole-3-carboxaldehyde (2b), 5-(4-methoxyphenyl)isoxazole-3-carboxaldehyde (2c), 1H-imidazole-2-carboxaldehyde and 2-butyl-4-chloro-1H-imidazole-5-carboxaldehyde, in ethanol, yielded the corresponding N'-heteroarylidene-1-adamantylcarbohydrazides 3a, 3b, 3c, 4 and 5, respectively, in good yields. The 4-acetyl-1,3,4-oxadiazoline analogues 6a‑c were prepared in 48-55% yields by heating their corresponding N'-heteroarylidene-1-adamantylcarbohydrazides 3a-c with acetic anhydride for two hours. Compounds 3a-c, 4, 5 and 6a-c were tested for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compounds 4 and 5 displayed potent broad-spectrum antimicrobial activity, while compounds 3a-c showed good activity against the Gram-positive bacteria.

Synthesis, antimicrobial and anti-inflammatory activities of novel 5-(1-adamantyl)-1,3,4-thiadiazole derivatives

New 1-adamanyl-1,3,4-thiadiazole derivatives namely, 5-(1-adamantyl)-1,3,4-thiadiazoline-2-thione 3, 5-(1-adamantyl)-3-(benzyl- or 4-substituted benzyl)-1,3,4-thiadiazoline-2-thione 4a-d, 5-(1-adamantyl)-3-(4-substituted-1-piperazinylmethyl)-1,3,4-thiadiazoline-2-thiones 5a-c, 2-[5-(1-adamantyl)-2-thioxo-1,3,4-thiadiazolin-3-yl]acetic acid 7, (±)-2-[5-(1-adamantyl)-2-thioxo-1,3,4-thiadiazolin-3-yl]propionic acid 9, 3-[5-(1-adamantyl)-2-thioxo-1,3,4-thiadiazolin-3-yl]propionic acid 11, N-[5-(1-adamantyl)-1,3,4-thiadiazol-2-yl]-N'-arylthioureas 15a-c and 5-(1-adamantyl)-1,3,4-thiadiazoline-2-one 16, were synthesized and tested for in vitro activities against a panel of gram-positive and gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compounds 7, 9, 15b and 15c displayed marked activity against the tested gram-positive bacteria, while compound 3 was highly active against the tested gram-negative bacteria. Compounds 4b, 7 and 15c were weakly or moderately active against C. albicans. In addition, the in vivo anti-inflammatory activity of the synthesized compounds was determined using the carrageenan-induced paw oedema method in rats. The propionic acid derivative 9 produced good dose-dependent anti-inflammatory activity.

3-(1-Adamant-yl)-1-{[4-(2-meth-oxy-phen-yl)piperazin-1-yl]meth-yl}-4-methyl-1H-1,2,4-triazole-5(4H)-thione

The title compound, C(25)H(35)N(5)OS, is a functionalized triazoline-3-thione with substituted piperazine and adamantyl substituents attached at the 2- and 5-positions, respectively, of a triazole spacer with an approximately C-shaped conformation of the mol-ecule. The piperazine ring adopts a chair conformation.

Synthesis and antimicrobial activity of new 5-(2-thienyl)-1,2,4-triazoles and 5-(2-thienyl)-1,3,4-oxadiazoles and related derivatives

New 5-(2-thienyl)-1,2,4-triazoles and 5-(2-thienyl)-1,3,4-oxadiazoles namely, N-[3-mercapto-5-(2-thienyl)-1,2,4-triazol-4-yl]-N'-arylthioureas 4a–e, 2-arylamino-5-(2-thienyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles 5a–e, 3-arylaminomethyl-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 7a–e, 3-(N-substituted anilinomethyl)-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 8a, b and 3-(4-substituted-1-piperazinylmethyl)-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 9a–f, were prepared. The synthesized compounds were tested for in vitro activities against certain strains of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compound 9a displayed marked broad spectrum antibacterial activity, while compounds 4d, 5e, 7b, 7c, 7d, 9b, 9c and 9d were highly active against the tested Gram-positive bacteria. None of the synthesized compounds were proved to be significantly active against Candida albicans.