Journal of Chemical Research

Advances in the chemistry of the organotin hydrides during the last decade are reviewed.

The reductive pinacol coupling of aldimines was studied in respect to different coupling-mediators such as mischmetall, Zn–Cu couple and Devarda alloy. High diastereoselectivity was achieved for three substrates. A simple procedure for the preparation of 1,2-diamines is described.

Alumina supported N-bromosuccinimide was found to be an efficient reagent for ring bromination of a number of aromatic compounds under solvent-free conditions. In the absence of the alumina the reactions are slow and some of the substrates are recovered unchanged. Under the reaction conditions aromatic oximes are converted into the corresponding carbonyl compounds. The method is simple, safe and rapid.

Acetylation and formylation of alcohols with acetic and formic acids have been carried out in the presence of catalytic amounts of Zr(HSO₄)₄ under mild and heterogeneous conditions.

In this paper, a series of pyrano[2,3-d]pyrimidine derivatives have been synthesised by the reaction of aromatic aldehydes, malononitrile and pyrimidine-4,6-diol in ionic liquid [bmim⁺][BF₄^-] at 80 °C. The structures of the products were characterised by IR, ¹H NMR spectra. Compared with other methods, ionic liquid is a green solvent, which has the advantages of easier work-up, milder reaction conditions, high yields and environmentally benign procedure.

A novel fluorescent chemosensor for the selective detection of zinc(II) in neutral aqueous solution has been synthesised by attaching the fluorophore into a macrocyclic polyamine (1,4,7,10-tetraazacyclododecane), and ion selectivity has been studied by fluorescence spectrocopy.

The first total synthesis of two unusual 5-deoxyflavone derivatives from Albizia odoratissima, 7,8-dimethoxy-3′,4′-methylenedioxyflavone 1 and 7,2′,4′-trimethoxy- flavone 2, has been accomplished.

A new 7,8–epoxydolabella–3(E)–12(18)–diene (1), diterpenoid together with three known compounds were isolated from a Honduras gorgonian Eunicea laciniata. The relative stereochemistry of 1 was established by spectroscopic studies and the antiprotozoal and antimicrobial activities of dolabellane diterpenoids 2–4 are reported. Three known cadinane type sesquiterpenes were also isolated from Honduras gorgonian Plexaurella nutans.

Hantzsch 1, 4-dihydropyridines (DHPs) were readily oxidised by zeofen (ferric nitrate and HZSM-5 zeolite) to the corresponding pyridines in good yields.

The reactive intermediate generated by the reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates was trapped by aromatic amides to produce unsaturated amidine derivatives in good yield.

The specific rates of solvolysis of trimethylsilylmethyl trifluoromethanesulfonate have been measured at 25.0 °C in ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) and their mixtures with water. Determinations were also made in aqueous acetone and in TFE–ethanol mixtures. An extended (two-term) Grunwald–Winstein equation correlation gave sensitivities towards changes in solvent nucleophilicity and solvent ionising power as expected for an S_N2 pathway, consistent with a previous proposal. For four solvents specific rates were determined at three or four additional temperatures and appreciably negative entropies of activation were observed, consistent with the proposed mechanism. At −20 °C, the specific rate of methanolysis is almost identical to that for methyl trifluoromethanesulfonate, suggesting a fortuitous balance between steric hindrance effects and a favourable electronic effect upon the introduction of the trimethylsilyl group.

A new (22R,23R)-2α,3α,22,23-diepoxy-5α-hydroxy-stigmastan-6-one diepisecasterone analogue have been synthesised from stigmasterol.

4–Aryl and 4–alkylaminocoumarins were prepared by reaction of 4–hydroxycoumarin with amines under microwave irradiation in solvent-free conditions in good to excellent yields.

New polydentate oxalamide-based ligands have been studied as chiral catalysts in the enantioselective addition of diethylzinc to benzaldehyde

A ¹H NMR spectroscopic study has shown the rate oxidation of dimethylarsinous acid to dimethylarsinic acid in buffered aqueous solutions to depend upon pH. Dimethylarsinous acid has been reported to be a highly toxic arsenical metabolite and component of the urine of persons exposed to inorganic arsenic, particularly through drinking water. As the pH of human urine can range from 4.5 to 8, the pH dependence of the oxidation rate of dimethylarsinous acid to dimethylarsinic acid has profound implications for the detection and analysis of these compounds in urine samples, and for the relevance of the experimental toxicology of dimethylarsinous acid.

Oxidation of a series of various primary and secondary benzylic alcohols with O₂ over [nBu₄N]₄W₁₀O₃₂/SiO₂ as a recyclable and green photocatalyst in CH₃CN resulted in the corresponding aldehydes and ketones selectively in high yields.

A novel class of biologically active compound 2,7-dihydro-3H-pyridazino[3′,4′:4,5]indolo[3,2-c]quinoline-3,13(12H)-dione (10a–b)has been achieved efficiently and quickly under solvent free conditions in an open vessel microwave system. The multi step one pot synthesis involved the reaction of 8,9,10,11-tetrahydro-6H-indolo[3,2-c]quinoline-6,7(5H)-dione (6a–d) and glyoxylic acid monohydrate followed by cyclocondensation with hydrazine hydrate under microwave irradiation. The synthesis of 8,9,10,11-tetrahydro-6H-indolo[3,2-c]quinoline-6,7(5H)-dione(6a–d) has also been described from the reaction of (2-oxo-1,2-dihydroquinolin-4-yl)hydrazine with 1,3-cyclohexanedione in the absence of any solvent/catalyst/strong acid or solid support using microwaves.

A mild and efficient method for the preparation of gem-diacetates from aldehydes with acetic anhydride is described using a catalytic amount of magnesium perchlorate giving excellent yields under solvent-free conditions.

m-Iodophenol (4a) was found to couple with 2-methylbut-3-yn-2-ol (5) in the presence of PdCl₂–CuI–Ph₃P-in triethylamine to afford 3-(3-hydroxy-3-methylbut-1-ynyl)phenol (6a), which was conveniently converted into m-ethynylphenol (7a). Under the same conditions, p-iodophenol did not couple with 5. However, p-iodo-1-[(tetrahydro-2H-pyran-2-yl)oxy]benzene (4b) did react with 5 to afford 1-[(tetrahydro-2H-pyran-2-yl)oxy]-4-[2-hydroxy-2-methyl-4-but-3-ynyl]benzene (6b), which was similarly converted into 1-[(tetrahydro-2H-pyran-2-yl)oxy]-4-ethynylbenzene (7b) with loss of acetone. Removal of the tetrahydropyranyl protecting group from 7b furnished p-ethynylphenol (8).

Under solvent-free conditions, one-step Beckmann rearrangement of a variety of ketones and aldehydes could proceed in the presence of alumina sulfuric acid (ASA). The ASA reagent can also be used for the preparation of keto- and ald-oximes.