Isolation and Crystal Structure of Novel by-products Observed During the Formation of bis(thiosemicarbazones)

Abstract

During the condensation of 4-methyl-4-phenyl-3-thiosemicarbazide (3) with 2,3-butanedione an unexpected byproduct, 8a-methyl-6,8a-dihydro-8-methyl-2-[N-methyl-N-phenylamino]-5H-1,3,4-thiadiazolo[3,2-d][1,2,4]triazine-5-thione, (5) was obtained in addition to the desired bis(thiosemicarbazone) (4). An X-ray crystal structure was obtained and is presented together with a proposed mechanism for its formation. A brief investigation of the coordination chemistry of bicycle (5) was carried out. The formation of cyclic compounds during the synthesis of analogues with extended backbones is also described.

Ligands for Molecular Imaging: The Synthesis of Bis(thiosemicarbazone) Ligands

“…However, when we tried to form the bis(thiosemicarbazone) from Me,Ph-thio-A C H T U N G T R E N N U N G semicarbazide and butanedione by heating the mixture under reflux in ethanol-water (1:1) for 2 h the bicyclic compound 67 was obtained. [77] Conjugation and Radiolabelling…”

Reactivity of Thiosemicarbazides with Redox Active Metal Ions: Controlled Formation of Coordination Complexes versus Heterocyclic Compounds

“…[26][27][28][29] We have found that the synthesis of both the free ligands and the complexes is complicated by the intraligand formation of cyclic products arising from coupling of the two thiosemicarbazone limbs. [30] For monothiosemicarbazones, interligand cyclisation occurs on reaction with methanolic ferric chloride or cupric perchlorate under reflux to yield heterocyclic compounds. [31] The reaction is highly substituent dependent and for R 2 = H, 1,3,4-thiadiazoles ( Figure 1E) are formed whereas for R 2 =…”

Synthesis, Radiolabelling and Confocal Fluorescence Microscopy of Styrene‐Derivatised Bis(thiosemicarbazonato)zinc and ‐copper Complexes

“…[14] Synthesis is often complicated by the formation of cyclic by-products which may be removed by recrystallisation from hot ethanol/water. [14,24,25] X-ray crystal structures of 2,3-butanedione mono(4-ethylthiosemicarbazone) and of the cyclic by-product, 4-ethyl-6-methyl-5-methylene-4,5-dihydro-1,2,4-triazine-3(2H)-thione have been obtained. Full crystallographic details are presented in the electronic Supporting Information (ESI).…”