Letters in Organic Chemistry - Volume 17, Issue 8, 2020

The aim of this review is an overview of diverse dialkyl zinc pro-chiral aldehydes addition reactions. One way of conducting asymmetric reactions is through the use of chiral catalyst. Therefore, new chiral ligands have attracted considerable attention in organic chemistry. Carbon-carbon bond formation reactions are an active research topic. The addition of dialkyl zinc to pro-chiral aldehydes is one of these popular reactions. Also, the chiral amino alcohols are important substrates for drug synthesis. These chiral ligands can be prepared by a simple synthetic way from easily accessible starting materials. This article reviews current catalyst reactions with the addition of dialkyl zinc to carbonyl compounds.

Under mild conditions, C3-quaternary 2H-pyrrolines can be convergently and efficiently assembled by Cu(II) and weak bases cocatalyzed [3+2] cycloaddition of 1,1-disubstituted alkenes and isocyanoacetates. Various functionalities can be tolerated, affording 2H-pyrrolines with up to two quaternary centers in a single step.

The reaction of substituted benzaldehydes with tribromoisocyanuric acid and triphenylphosphine led to the corresponding benzylidene dibromides (95-99%). Similar reaction using trichloroisocyanuric acid produced benzylidene dichlorides (38-96%).

Methyl eugenol olefin metathesis was conducted with non-carbene Ru-complexes ([RuCl2(PPh3)2amine]) in the absence and presence of SnCl2 or CuCl2 as additives and their catalytic activities were compared with that of a commercial Grubbs catalyst 2nd Generation (G2).

A series of alumina supported Ru nanoparticles (Ru γ -Al2O3-x (x=2-10 Ru wt%) was synthesized using the ethylene glycol reduction method. XRD, TEM, EDX, H2-chemisorption, XPS and H2-TPD analytical techniques were used to understand the physiochemical nature of alumina supported Ru nanoparticles. All the well-characterized Ru#Al2O3-x (x=2-10 Ru wt%) catalysts were used for high-pressure CO2 hydrogenation to formic acid synthesis. A clear correlation was recorded between the physiochemical properties of developed catalysts and the molar quantity of formic acid. Among all the developed catalysts, Ru#Al2O3-2 catalyst with or without ionic liquid reaction medium gave a good molar quantity of formic acid. Application of ionic liquid was also expanded, and ionic liquid medium appeared as a good solvent system as compared to the amine solvent system, which not only provides better solubility of reactants and catalysts but also found useful in the easy recovery of formic acid after the completion of the reaction. The catalyst recycled seven times with easy product isolation stem to make this system very useful and fulfill the requirement of sustainable chemistry.

Metal-free synthesis of pyrimidinone (alky/aryl) via Biginelli reaction in the presence of aqueous sodium dichloroiodate (NaICl2) was studied under reflux conditions. Herein, we first time report the synthesis of the aliphatic Biginelli product by using aliphatic aldehyde, cyclopentane, and urea. Several aromatic and heteroaromatic aldehydes were studied for the confirmation of the wide applicability of aq. NaICl2 for the synthesis of corresponding Biginelli products. The obtained desired products provide good to excellent yield.

2-((E)-((4-((4-methoxyphenyl)ethynyl)phenyl)imino)methyl-4-((E)phenyldiazenyl)phenol (1) have been synthesized and characterized. X-ray single crystal diffraction study of the compound 1 reveal a monoclinic structure. Room temperature luminescence is observed for 1 in CH2Cl2 solution due to π* → π transition. The SHG efficiency by Kurtz powder technique indicating the compound 1 displayed the second harmonic generation (SHG) property.

One-pot tandem oxidation and double Diels-Alder reaction of myrcene or ocimene with in situ generated 1,4-benzoquinone or 1,2-benzoquinone at 0°C for 1.5 h yielded polyalkylated 1,4,4a,5,8,8a,9a,10a-octahydro-9,10-anthracenediones and bis(alkylated) 9,10-phenanthrenedione respectively. The structure of novel bis-adduct from ocimene, (1R,4aR,5S,8aS,9aS,10aR)-rel- 1,4,4a,5,8,8a,9a,10a-octahydro-2,6-dimethyl-1,5-bis(3-methyl-2-buten-1-yl)-9,10-anthracenedione, was elucidated through single crystal X-ray analysis.

A simple and practical method for the synthesis on a large scale of altretamine (1), a wellknown antitumor drug, has been successfully developed. The synthesis method involves the conversion of cyanuric chloride (2) into altretamine (1) by dimethylamination of 2 with an aqueous solution of 40% dimethylamine and potassium hydroxide in 1, -dioxan 4in one step to give altretamine (1) in high yield.

Pyrazoles, Schiff bases and the quaternary ammonium compounds (QAC) such as N-alkyl substituted azachalcones are the important group of chemical individuals with widespread usage in many fields of science. In particular, these compounds have proven biological activities. In addition, the emergence of resistance against antibiotics used is the cause of an increasing necessity of new effective substances. Therefore, new N-alkyl substituted derivatives (4-7), 1,3,5-trisubstituted-2- pyrazoles (8-10) and Schiff bases (11-13) with biological activities such as phenolic. antioxidants or QAC were synthesized, starting from azachalcones. The structures of the compounds were elucidated with spectral methods including IR, 1H-NMR, 13C-NMR, COSY spectral data and elemental analyses. The prepared compounds were evaluated for antibacterial activity against four Gram-positive bacteria, and four Gram-negative bacteria. The minimum inhibitory concentration (MIC) of the N-alkylated azachalcone derivatives 5 and 7 (7.8 mg/mL) showed strong antimicrobial activities, especially against Bacillus cereus. Antioxidant capacities of the synthesized compounds were determined by using CUPRAC and FRAP methods. As a result, compound 9 was observed to be more effective than other compounds.

The reaction of bis-(4,6-dichloro-[1,3,5]triazin-2-yl)-diazene with furan proceeds with the formation of inverse electron demand Diels-Alder product with a high yield. M06 2X/6 31G(d,p) calculations show thermodynamic instability of “normal” DA reaction product and predict its [3,3] sigmatropic rearrangement to the thermodynamically more favorable formal IEDDA reaction product. The obtained NMR spectra were in good agreement with GIAO calculations and were in accordance with DFT thermochemical data that confirmed the formation of the described product. IR and UV/Vis spectral data was also obtained and discussed.

α-Amino acid chlorides are reactive coupling agents in amide (peptide) formation. The Vilsmeier reagent ((chloromethylene)dimethylammonium chloride) offers a convenient way to prepare α-amino acid chlorides for peptide synthesis. Its use with N-trifluoracetyl (TFA)-protected isoleucine and allo-isoleucine is described. The 1H-NMR of the α-proton signal offers a convenient way to monitor the chirality retention in the acid chloride forming reaction and subsequent Friedel-Crafts acylation of arenes which result in α-amino acid aryl-ketone with no loss of chirality.