Journal of Chemical Research

Organotin compounds find a bigger range of technological and industrial applications than the organic compounds of any other metal. Many of these applications involve catalysis or anticatalysis, often in polymer chemistry, and they have an importance out of all proportion to the tonnage of tin which is used. This article reviews the present standing of the non-biological applications of organostannanes, with an emphasis on the mechanisms of the reactions which are involved.

An efficient synthesis of the angiotensin II inhibitor Valsartan (Diovan) is presented. The formation of the aryl–aryl bond represents the key step of its synthesis, which has been done by a Suzuki coupling of aryl boronate with 2-bromophenyl oxazoline with good yield and purity. This method overcomes many of the drawbacks associated with the previously reported syntheses.

Ionic liquid-supported [bis(trifluoroacetoxy)iodo]benzene, a useful chemical reagent for organic synthesis, was synthesised in high yields using three different methods. The product was found to be stable in air and in a high humid atmosphere over a few weeks. The chemical structure of the product was characterised by ¹H NMR, ¹³C NMR, ¹⁹F NMR, IR, MS and elemental analysis.

L-Proline triflate has been used as an efficient catalyst for an improved and rapid one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles in good yields. The benefit of this approach is its operational simplicity and the catalyst can be easily recovered and reused without any loss of activity.

Various 4′-aryl-5′-phenyl-2′,4′-dihydrospiro[indole-3,3′-[1,2,4]triazol]-2(1H)-ones have been synthesised by reaction of amidrazones with 2-(2-oxoindolin-3-ylidene)malononitrile.

Ceric ammonium nitrate efficiently catalyses the reaction of acenaphthenequinone with indoles afforded symmetrical 2,2-bis(1H-indol-3-yl)acenaphthen-1(2H)-one in excellent yields within 2h under ethanol refluxing, as well as 2-hydroxy-2-indolylacenaphthen-1(2H)-one with indoles afforded the corresponding unsymmetrical 2,2-bis(1H-indol-3-yl)acenaphthen-1(2H)-one. This provides an efficient route to the synthesis of symmetrical and unsymmetrical 2,2-bis(1H-indol-3-yl)acenaphthen-1(2H)-one derivatives.

The chemical investigation of the aerial parts of Pteris semipinnata afforded a new ent-kaurane diterpenoid glucoside, pteriside (1), and three known sesquiterpenoids, namely (2R)-pterosin B (2), (2S, 3S)-pterosin C (3) and pterosin C 3-O-β-D-glucoside (4). The structure of 1 was established by spectral methods, especially two dimensional NMR techniques.

A rapid, efficient and eco-friendly method for the preparation of new aryl-1,4-bisoxyacetylhydrazone molecular tweezers was reported. The reaction is accelerated by microwave irradiation under solvent-free conditions in the presence of solid Al₂O₃. The structures of these new molecular tweezers were characterised by ¹H NMR, IR, MS spectra and elemental analysis.

PdCl₂ combined with TBAF (n-Bu₄NF) were found to be efficient conditions for the Heck reactions. In the presence of PdCl₂ and TBAF, a variety of aryl halides were coupled with alkenes smoothly in moderate to good yields. Moreover, the PdCl₂/TBAF system could be recovered and reused several times in the reaction. Note that these reactions are conducted under solvent-free, ligand-free and reusable conditions.

A novel method was developed to synthesise azoarenes from nitrosobenzenes under mild conditions. Samarium (II) iodine was used to achieve the N–N coupling. The method also provides evidence for the proposed mechanism involved in the reduction of nitro compounds to the amines with SmI₂.

A new rhodamine-based chemosensor 2, which shows a reversible dual fluorogenic and chromo-response to Fe³⁺ in MeOH-HEPES buffer (10 mM, pH 7.4) (3:1 v/v), has been developed. The free solution of 2 is colourless and nonfluo-rescent which changes to pink with a strong fluorescence in the presence of Fe³⁺. Other metal ions (Hg²⁺, Ag⁺, Pb²⁺, Sr²⁺, Ba²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Cu²⁺, Zn²⁺, Ce³⁺, Cr³⁺, Mg²⁺, K⁺ and Na⁺) had no significant effect.

1-Naphthoylisothiocyanate (1) is used as a building block in the synthesis of 1,2,4-triazole, quinazoline, benzothiazole and thiourea derivatives. The antimicrobial activity of some of the synthesised compounds was tested.

An efficient and practical demethylation of ortho substituted aryl methyl ethers using AlCl₃ has been developed. This method gives a high conversion, is simple to operate and is cost-effective. A mechanism involving the complexation of AlCl₃ with the OMe and the adjacent electron withdrawing group is proposed. Many functional groups can be tolerated in the demethylation process, and 29 examples gave a demethylated product in a yield of 90–98%.

Reaction between 1,1,1-trifluorobutane-2,4-dione derivatives and electron-deficient ethyl phenylpropyolate in the presence of triphenylphosphine leads to 4-acyl-2-phenyl-3-trifluoromethylcyclobut-2-ene-1-carboxylate derivatives in good yields.

An efficient asymmetric synthesis of Sitagliptin, a new DPP-IV inhibitor for the treatment of type 2 diabetes mellitus has been developed. The beta-amino acid fragment of Sitagliptin was prepared by asymmetric Michael addition of the corresponding α, β-unsaturated ester to (R)-(α-methylbenzyl)benzylamine followed by a two-step elaboration to obtain N-boc beta-amino ester. Hydrolysis of the ester and coupling with the triazolopiperazine afforded Sitagliptin after cleavage of the N-boc group and salt formation. The overall yield was 31% over nine steps.

A series of 10 related benzofuran neolignan derivatives were obtained by utilising a biomimetic reaction sequence involving oxidative dimerisation of methyl ferulate, followed by derivatisation reactions. The structures of the new compounds were confirmed by ¹H NMR, elemental analysis, MS and IR. All compounds were evaluated for their cytotoxic potential against five human cancer cell lines (HL-60, SMMC-7721, A-549, SK-BR-3 and PAN-1) by the standard MTT method. The results showed that most of them exhibit potent cytotoxicity.

The problem associated with electrolytic deprotection, which is a concern in the total synthesis of shikonin, is solved by the addition of Cu2+ to the electrolysis system. The improvement has three advantages: first, it practically increased the yield from 40 to 85%; second, the isolation of shikonin became much easier. Third, the reaction time was significantly shortened.

Iodine mediated condensation of 3-acetyl-6-substitutedcoumarin (1) with 3-alkyl/aryl-4-amino-5-mercapto[1,2,4]triazoles (2) have been found to give 3-alkyl/aryl-6-(6-substituted-2-oxochromen-3-yl)-7H[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines (3a-n) directly in one step. The reaction has also been carried out using microwave irradiation. This protocol is an improvement on reported methods as it occurs in a single step and avoids the use of highly lachrymatory molecular bromine.