Nitration, and Chlorination of Aromatic, and Heterocyclic Compounds, using Tetrachlorosilane
The development of a new silane reagent derived from tetrachlorosilane (TCS) was applied in the present work. TCS-sodium nitrate (NaNO3) binary reagent and zinc chloride (ZnCl2) were reported here as a homogeneous nitrating system. The later was used for the efficient mono nitration, in most cases, with high para-regioselectivity. The nitration proceeded smoothly under mild condition, fairly clean and in good yields. This readily available and inexpensive system is superior to other methods by avoidance of the use of corrosive nitrating reagents and therefore considered to be convenient in terms of risk reduction, economic advantages and environment protection. The present protocol was convenient and applicable to a variety of aromatic hydrocarbons and could be amenable to high throughput synthesis of combinatorial libraries for potential drug development, which needs to be studied as part of future investigations.
Abstract: An efficient and regioselective nickel-catalyzed remote C–H nitration of 2-aryloxazoline amides using the non-corrosive tert-butyl nitrite (TBN) as nitro source has been developed. The protocol makes use of inexpensive nickel salts as catalysts and delivers the corresponding products in excellent yields. Notably, bis-nitration products were obtained by simply increasing the amount of tert-butyl nitrite. This reaction proceeds in air and features excellent functional group compatibility, broad substrate scope and is suitable for gram-scale synthesis.
Pub.: 17 Jul '17, Pinned: 30 Jul '17
Abstract: An unprecedented copper-catalyzed in situ azidation-oxidation for the nitration of anilides and sulfonamides has been developed by direct CAr-H functionalization. This novel and efficient nitration protocol is achieved employing TMSN3 and TBHP without the exclusion of air or moisture. The synthetic applications of the 2-nitroanilides have been explored.
Pub.: 22 Jun '17, Pinned: 30 Jul '17
Abstract: Synthesis and kinetics of potassium periodate(KIO4)/NaNO2/KHSO4)-initiated nitration of aromatic compounds have been studied in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds is achieved under conventional and solvent-free microwave conditions. Reaction times in microwave-assisted reaction are comparatively less than in conventional reaction. The reaction kinetics for the nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [phenol], [NaNO2], and [KIO4]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration increased in the solvent of high dielectric media (solvents with high dielectric constant (D)). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D − 1)/(2D + 1)]. These observations probably indicate the participation of anionic species and molecular or (dipolar) species in the rate-determining step. In addition, the plots of (log k′) versus volume% of organic solvent were also linear, which probably indicate the importance of both electrostatic and nonelectrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups, but results could not be quantitatively correlated with Hammett's equation and depicted deviations from linearity. These deviations could probably be attributed to cumulative effects arising inductive, resonance, and steric effects. Leffler's plot (ΔH# vs. ΔS#) was found linear indicating the compensation (cumulative) effect of both enthalpy and entropy parameters in controlling the mechanism of nitration.
Pub.: 12 Jun '17, Pinned: 30 Jul '17
Abstract: A cobalt-catalyzed proton-coupled electron transfer (PCET) mediated regioselective ortho-specific nitration of aromatic C(sp2)-H bonds using chelation assisted removable vicinal diamine directing groups has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2•4H2O as the catalyst and AgNO2 utilized as nitro source as well as terminal oxidant in the presence of O2 as a external oxidant, no external base and additives were required for this process. By doing controlled experiments and mechanistic investigations with DFT calculations revealed that the reaction proceeds through PCET promoted nitro functional group transfer pathway. Moreover the produced compounds are valuable and pharmaceutically quite relevant.
Pub.: 22 Jun '17, Pinned: 30 Jul '17
Abstract: A Co-catalyzed highly chemo- and regio-selective nitration of C(sp(3))-H was developed. Diverse aliphatic nitro compounds were obtained in good yields, using t-BuONO as a nitrating reagent. Specific nitration of C(sp(3))-H instead of C(sp(2))-H was achieved via a radical process rather than concerted metalation-deprotonation.
Pub.: 20 Jul '17, Pinned: 30 Jul '17
Abstract: 2,2'-Dinitramino-5,5'-bi(1-oxa-3,4-diazole) (2) is a new highly energetic material with superior calculated detonation performance in comparison to cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) and penta-erythritoltetranitrate (PETN) and can be prepared by an economical and practical two-step synthesis. The starting material 2,2'-diamino-5,5'-bi(1-oxa-3,4-diazole) (1) is synthesized by the reaction of oxalyl dihydrazide with cyanogen bromide. Nitration of 1 yields the title compound in perfect yield and purity. The combination of its high density of 1.986 g cm(-3) , the positive heat of formation (+190 kJ mol(-1) ), and a slightly positive oxygen balance (+6.2 %) results in ideal calculated detonation parameters (e.g. detonation velocity 9296 m s(-1) ). The sensitivities toward impact and friction can be adjusted by deprotonation and formation of corresponding nitrogen-rich salts, for example, ammonium (3), hydroxylammonium (4), and guanidinium (5) salts.
Pub.: 22 Jul '17, Pinned: 30 Jul '17