A 2,2-Bis(ethoxycarbonyl) vinyl- (BECV) group was used for the selective protection of amines at room temperature in the presence of potentially interfering functional groups such as OH, SH, COOH as well as other NH(2) groups. Several functional group transformations such as esterification, O-alkylation, O-acylation, N-alkylation, N-acylation, S-alkylation can selectively be carried out in the presence of the BECV group. The selective deprotection of the BECV group was achieved in a short time using ethylenediamine at room temperature while several other functional groups such as benzoate, aliphatic esters, amides and ethers remain intact. The BECV group shows orthogonal stability against the common protecting groups such as Fmoc, Cbz and Boc.
A series of functionalized malonic acid half-ester derivatives (parent compound MHE-1), with variations in functional groups at different positions on the aromatic ring, have been synthesized and crystal structures are determined at room temperature (296 K). The methyl IJ4-CH 3 , MHE-2) and chloro (4-Cl, MHE-3) derivatives are isomorphous with each other. The overall crystal packing of MHE-1-3 is similar. However, there are few differences observed between stacking of layers in these structures. Compounds with nitro IJ3-NO 2 , MHE-4) and ethyl ester IJ2-COOC 2 H 5 , MHE-5) substituents crystallize in different space groups and thus crystal packing is different when compared to MHE-1-3. In all the structures, intramolecular N-H⋯O and O-H⋯O hydrogen bonds generate a two fused SIJ6) ring motif. A detailed study is carried out to visualize intermolecular interactions observed in all five crystal structures (MHE-1-5) using Hirshfeld surface (HS) analysis with two dimensional fingerprint plots. The relative contribution of intermolecular H⋯H contacts in MHE-3 is substantially lower than that in MHE-1-2, though similar crystal packing arrangements of MHE-1-3 and MHE-2 and MHE-3 are isomorphous. From HS analysis it is clear that the observed H⋯H contact contribution (MHE-3) is a consequence of the presence of the chlorine substituent and growing contribution of Cl⋯H contacts. The relative contributions of other intermolecular contacts involving various atoms are comparable in MHE-1-3 structures. The intermolecular interaction energies are quantified using PIXEL for various molecular pairs extracted from respective crystal structures. Interestingly, there are some invariant and variable intermolecular contacts observed between different groups in all five structures.
In this work, employing the Hibiscus rosa sinensis (HRS) flower extract as a green reducer for graphene oxide (GO) reduction and functionalization of rGO using piperazine is proposed. A chemically modified screen-printed carbon electrode (SPCE) was prepared using piperazine functionalized reduced graphene oxide (P-rGO). Electroanalytical techniques such as amperometry and differential pulse voltammetry (DPV) were used to investigate the sensing capability of P-rGO modified SPCE towards the detection of Hg 2 + ions. The oxidation peak observed in the cyclic voltammetry was due to the interaction between piperazine (amine) and mercury ions. Piperazine plays a major role in improving the sensitivity of the developed sensor towards mercury cation detection, while the P-rGO is used as a platform for the incorporation of Hg 2 + .The developed sensor exhibits a high sensitivity of 0.00327 μA/pM over a wide linear range of 0.2 pM to 2 pM, with a detection limit of 0.0557 pM.
A biosynthesis of Copper Nanoparticles supported on Zeolite Y and its application as efficient, reusable, heterogeneous catalyst in C−N cross coupling reactions between amines and aryl halides are reported. The biosynthesis of CuNPs/Zeolite Y was achieved by the reduction of CuSO4.5H2O with the lemon juice (without peal) and encapsulated into the Zeolite Y in a single step. In this biosynthetic method, the ascorbic acid present in the lemon juice acted as a reducing agent for CuSO4.5H2O. The CuNPs/Zeolite Y was characterized using UV‐Vis, powder XRD, FT‐IR, HR SEM, EDS and TGA. The average size of the CuNPs are found to be 50 nm and has large surface area for the efficient catalysis. The new catalyst is effect in catalyzing the C−N cross coupling reaction between amines and aryl halides (yield ranging from 89% to 95% depends on amine and aryl halide used). The catalyst can be recovered from the reaction mixture by simple procedure. The recovered catalyst is found to be active in catalyzing the coupling reaction even after five runs.
Geminal diesters,vinylamines, were found to undergo selective hydrolysis in the presence of BF 3 •OEt 2 at room temperature to give the corresponding half esters. Neighboring group participation by nitrogen in the hydrolysis was observed. This method is useful for the preparation of highly functionalized malonic acid half esters.
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