Letters in Organic Chemistry - Volume 1, Issue 3, 2004

Dear Readers, I am pleased to present the first “News andViews in Organic Chemistry” (we use tocall it “N & V”), a new vibrant andexclusive feature of Letters in OrganicChemistry (LOC) that will provide timelyinformation of new scientific advances, asreported in the most exciting recentpapers published in the organic chemistryliterature. The articles will be selectedafter a careful review of the recentliterature on th Read More

Intramolecular reductive deoxygenation of ethylenedioxy tethered symmetrical and unsymmetrical aromatic bis(ketone) ethers with the low-valent titanium (LVT) reagent (TiCl4-Zn-DME) yielded the corresponding cyclic stilbenes with excellent Z-selectivity. On the other hand, coupling of the aldehydic tethered ethers proceeded with high E-selectivity with the LVT reagent (TiCl3 / Li / KCl (2.0 eq.) / THF). Dealkylation of the cycli Read More

A small library of aryl and dialkyl 3-hydroxy thiophene 2-oxazolines was simply prepared by direct and selective metalation of 4-tertbutyl-2-(thiophene-2-yl)-4,5-dihidrooxazole and its successive reaction with aromatic and aliphatic ketones. The ligand 7h was able to promote the addition of Me2Zn to aromatic aldehydes with good enantioselectivity (up to 92 % ee).

Lewis acid mediated rearrangement of alkoxybenzyl allyl ethers into aldehydes in moderate to good yields, catalysed either by Yb(OTf)3 or ZrCl4 is reported. The ZrCl4 catalysed transformation offers mild and easily adaptable clean reaction conditions and good yields of the products. Additionally, ZrCl4 catalysed rearrangement under solvent free conditions is an advantageous modification.

Via the Ugi 4-centre 3-component reaction (U-4C-3CR), bicyclic cis-2-azetidinone derivatives were synthetised from cyclic β-amino acids on Super Acid Sensitive Resin (Sasrin). 2-, 3- or 4-Formylbenzoic acid was immobilised on the resin through its carboxy function. The U-4C-3CR was also carried out in solution, making use of scavenger resins for purification.

The unknown pyrrolo[2,1-c][1,2,3]triazolo[1,5-a][1,4]benzodiazepin-8-one ring system has been synthesised starting from the N-Boc-L-proline methyl ester. The totally diastereoselective intramolecular 1,3- dipolar cycloaddition of the azide 9 constitutes the key step of the synthetic sequence.

Solid-phase methods for the preparation of hydantoins are reviewed. Furthermore, an optimized method based on the concourse of 1,1'-carbonyldiimidazole allows the preparation of hydantoins without loss of chiral integrity.

Random copolymers of polystyrene were functionalized with diamidopyridine and anthracene recognition elements. Cooperative recognition between isobutyl flavin “guest” molecules and mixed recognition unit modified “host” copolymers was observed arising from a combination of aromatic stacking and hydrogen bonding interactions.

A copper bronze-mediated carbazole arylation reaction under mild reaction conditions is reported. Yields of 9-arylcarbazoles achieved are nearly quantitative and almost independent of the nature of the substitution on the carbazole or the aryl halide. A series of 9-arylcarbazole derivatives have been synthesised and their luminescence studied.

Synthesis of (2-methoxy-5-dihydroxyborylphenyl)alanine, (2-butoxy-5-dihydroxyborylphenyl) alanine, and (2-methoxy-4-dihydroxyborylphenyl)alanine for Boron Neutron Capture Therapy is described. In the key step, the amino acid functionality was introduced by the Wittig reaction. The approach provides a general access to alkoxy substituted boronated phenylalanines.

This paper deals with the synthesis of α-substituted enol ester derivatives of adenosine 5'- phosphate. These compounds were formed by the Perkow reaction of α-chloromethyl ketones with an in situgenerated adenosine-5'-yl bis(trimethylsilyl) phosphite intermediate. Among these reactions, the use of α- chloro-2',4'-difluoroacetophenone gave predominantly the enol phosphate derivative over the Arbuzov reaction Read More

The synthesis and utility of a novel, m-hydrobenzoin derived chiral auxiliary in stereoselective α- alkylation reactions using convenient solution chemistry as well as the attachment of an analogous system onto a solid support and its application as a dual chiral auxiliary and linker is described.

The efficient chemoenzymatic synthesis of a (R)-3,4-diaminobutanoic acid derivative has been achieved. The final compound has suitable orthogonal protection for solid phase peptide synthesis.

The reactivity of pyrrololactone 3 towards reductive and alkylating agents has been studied and the synthesis of diverse α, β'-difunctionalised pyrroles is presented. The ambivalent reactivity of compound 3 towards the different nucleophilic reagents has been rationalised.

Synthesis of new octahydrodibenz[b,f]azepin-10-one derivatives by a two-step synthetic route based on 2-carbethoxymethyl cyclohexanone reactivity is reported.

Cesium fluoride (CsF) catalyzes the addition of trimethylsilyl cyanide (TMSCN) to various aldehydes. Aromatic, aliphatic, cyclic and heterocyclic aldehydes have been converted into the corresponding trimethylsilyl ethers. Most of the aldehydes show over 99% yield for 20min. The mechanism of silylcyanation has been proposed.

Highly diastereoselective methylation of (2S,4S)- and (2R,4S)-3-tert-butyl 4-methyl 2-tertbutyloxazolidine- 3,4-dicarboxylate (1a / b) is reported. The relative and absolute configuration of the methylated products was assigned by NOESY and confirmed by a crystal structure of 1a.

The singlet oxygen oxygenation of 2-(α-C-glucopyranosyl)furans 1 leads readily and diastereoselectivity to the corresponding endoperoxides 2 whose fate can be controlled. Compounds 2 thermally rearrange into cis-dicarbonyl-α-O-glucosides 3 while by reduction they afford the cis-C-analogs 5. The latter readily convert to trans-8, which by silica gel chromatography tautomerize into β-anomers 9.

The straightforward synthesis of calix[4]crown derivatives in excellent yields under non-diluted reaction conditions is described. The reactions proceed smoothly at ordinary temperature and substrate concentrations of up to 1 M. Theoretical calculations on the reaction intermediates indicate that preorganization originating from the coordination of oxygen atoms to sodium ions plays an important role in the reaction

This Letter reports the collapse and subsequent self-reassembly of mesoscopic architectures of supramolecular J aggregates in solution. Ultrasonication of the string-like 5,5'-dichloro-3,3'-disulfopropyl thiacyanine (TC) J aggregates caused fragmentation (collapse) of the initial morphology, followed by a prompt self-reconstruction into mesoscopic rod-like architectures. Fluorescence microscopy, polarized light Read More