On the Reactivity of 1H‐Pyrazino[2,3‐c][1,2,6]thiadiazine 2,2‐Dioxide and Derivatives: Nucleophilic Substitution, Amination, Aldol‐Type Condensation, Oxidation, and Hydrolysis

Abstract

The reactivity of the 1H‐pyrazino[2,3‐c][1,2,6]thiadiazine 2,2‐dioxide system, structurally related to pteridine, was studied, and a number of novel derivatives were synthesized. The chemical behaviors of these two related fused polyaza systems were compared.

Cyclopentathiadiazines, Cyclohepta‐ and Cyclopentadithiazoles: New Materials and a Rich Heterocyclic Chemistry of Cyclic Enaminonitriles

“…The presence of a chlorinated isothiazole and a 1,2,3-dithiazole, both fused to the chlorinated cyclopentadiene ring, could therefore satisfy all the spectral features. Single-crystal X-ray diffraction confirmed the structure of 9 as the first example of an isothiazolo [3,4-d]cyclopenta [1,2,3]dithiazole, a new heterocyclic system ( Figure 2). The molecules in the solid state showed close contacts between the three sulfur atoms and one nitrogen atom in one direction, and between one of the chlorine atoms and one of the nitrogen atoms in the orthogonal direction, but there are no close contacts with the remaining chorine atom.…”

“…This time the presence of one aromatic proton in the 1 H NMR spectrum of 10, confirmed by 13 C NMR spectroscopy, the presence of a strong absorption due to a cyano group in its IR spectrum and the MS and analytical data, showed the presence of the partially chlorinated 4-cyanocyclopenta[1,2,3]dithiazole system. Therefore this method offers a new alternative route to the preparation of cyclopenta [1,2,3]dithiazoles, which are usually obtained from oximes.…”

“…All the reported polycyclic 1,2,6-thiadiazines, except for the naphtho-and naphthobis [1,2,6]thiadiazines, [8] have been prepared from preformed 3,5-dichloro-4H-1,2,6-thia-nocyclohept-1-enecarbonitrile reacted with SCl 2 , iBu 3 N and NCS to give a formally antiaromatic cyclohepta [1,2,3]dithiazole. Some of the compounds obtained showed characteristics useful as new materials, for example, as liquid crystals and near-infrared dyes.…”

“…[7] Cyclopenta [1,2,3]dithiazoles, [9] cyclopenta [1,2]dithioles and cyclopenta [1,2]thiazines [10] have been prepared by several methods that involve the reaction of simple saturated ketoximes with disulfur dichloride. We have reported a related procedure that is suitable for the one-pot preparation of the first cyclopenta [1,2,6]thiadiazines by the reaction of indene and cyclopentene enaminonitriles and sulfur dichloride (SCl 2 ).…”

“…[1] Bentazone [3-isopropyl-1H-2,1,3-benzothiadiazine-4(3H)-one 2,2-dioxide] is a well-known, highly active and selective herbicide of long-standing that has been routinely used as a post-emergence herbicide for the control of broad-leaf weeds and some grasses. [2] The 1H-pyrazino [2,3-c] [1,2,6]thiadiazine 2,2-dioxide system, [3] which is structurally related to pteridine, is of considerable pharmaceutical interest since some of its derivatives have shown interesting properties as diuretics, platelet aggregation inhibitors, [4] and bronchodilator agents [5] whilst benzyl derivatives of benzothieno[3,2-a]thiadiazine 2,2-dioxides act as phosphodiesterase 7 inhibitors.…”