Letters in Organic Chemistry - Volume 5, Issue 3, 2008

Enynols were hydroaluminated and cross coupled with aryl iodides. Reduction of the yne portion of the enynol is a serious side reaction so reaction conditions to minimize reduction and maximize cross coupling were investigated in detail.

Copper triflate was used as catalyst for the addition of pyrrole to 2-benzylidenemalononitrile and its substituted derivatives. 2-Alkylated pyrrole derivatives were regioselectively obtained in mild reaction conditions. The addition reactions were found to be highly dependent on the substituents of the phenyl group.

Regioselective synthesis of oxepin and oxocin annulated quinoline heterocycles by the combination of Claisen rearrangement and ring-closing metathesis reaction is described. The ring-closing metathesis (RCM) and ring-closing enyne metathesis (RCEM) proceeded smoothly in the presence of Grubbs' catalyst A or B in toluene under nitrogen atmosphere without deactivation of the basic quinoline nitrogen.

Ln-N complexes are important catalysts for organic synthesis and polymerization. This review describes the progress on a series of Ln-N complexes, as well as the recent applications of these complexes in hydroamination/ cyclization, hydrosilylation, polymerization, hydrophosphination/cyclization, and the Tischenko reaction.

Nabumetone is efficiently and economically prepared from hydrogenation of 3-methoxycarbonyl-4-(6- methoxy-2-naphthyl) but-3-en-2-one catalyzed by Raney Ni (W-2) under 145.0 psi H2 at 45 C and subsequent acid hydrolysis in 88.1% yield and 99% purity (GC). A high vacuum distillation or rectification purification method is used to improve the whole qualification of nabumetone.

An efficient acetylation and tert-butoxycarbonylation (Boc) of carbohydrate derivatives, phenols and amines catalyzed by tetrabutylammonium bromide is reported. The reaction condition is applicable to substrates containing acid and base labile functional groups. In most of the cases yields obtained were excellent.

A new efficient method for the preparation of 2-aryl-4,6-dinitroindoles based on reductive cyclization of E-2- azido-4,6-dinitrostilbenes under the action of FeCl3 6H2O - NaI system - in the CH3CN media at room temperature has been developed.

Starting from easily available (+)-norcamphor and according to an established approach, the 2-benzo[b]furyl hydroperoxide exo-5 was obtained in 58% overall yield. In order to ascertain the impact of the modification on the activity of this chiral oxidant, a study was carried out employing it in the asymmetric epoxidation of an allylic alcohol and α,β- enones.

Henry reaction can be accelerated by basic ionic liquid 1-methyl-3-butylimidazolium hydroxide ([bmIm]OH) as catalyst and reaction medium with good yields in short time at room temperature. This strategy is general and works with a broad range of aldehydes. The recovered [bmIm]OH can be recycled with consistent activity.

The Wenker reaction is an efficient and practical method for the synthesis of NH-aziridines from vicinal amino alcohols. However, some limitation in the application has been reported. The scope and limitation of the Wenker reaction were investigated with a series of structurally diverse and representative vicinal amino alcohols.

Regioselective synthesis of a hitherto unreported thiocoumarin-annulated furopyran moiety was achieved by the application of Claisen rearrangement in which a second Claisen rearrangement was achieved by anhydrous aluminum chloride. The precursor endocyclic compounds for catalyzed Claisen rearrangement were synthesized by the thermal [3,3] sigmatropic rearrangement of the corresponding ether.

An ecofriendly, microwave (MW) promoted and solventless method is described for the alkylation of diethyl malonate, ethyl acetoacetate and ethyl cyanoacetate by a variety of alkyl halides in the presence of K2CO3. In the solidliquid phase alkylation of active methylene containing substrates, it seems to be of general value that the phase-transfer catalyst, that is an onium salt in the present case, can be omitted and substituted by MW irradiation promoting the formation of the potassium salt of the substrate and its transfer to the organic phase. In certain cases, the use of triethylbenzylammonium chloride led to the formation of by-products under the conditions (∼160 ° C/∼12 bar) applied.

To develop a methodology for bone-specific delivery of drugs, a bone-targeting gem-bisphosphonate was used as a carrier of drugs. We had synthesized five compounds, which were a new class of potential bone-targeting reagents for bone tumors consisting of melphalan linked to a gem-bisphosphonate moiety through an amide linkage. The conjugates showed a high affinity to hydroxyapatite in vitro.

A concise formal synthesis of (±)-shikonin via a highly α-regioselective prenylation is achieved. The novelty of the procedure lies in the introduction of side chain of shikonin in one step via prenylation of 1, 4, 5, 8- tetramethoxynaphthalene-2-carbaldehyde under mild conditions without producing any γ-isomer.

An efficient synthesis of calix[4]pyrroles that uses soft conditions and bismuth salts, which are relatively nontoxic, readily available and inexpensive, is described.

A series of β-aminosulfones were synthesized with high enantioselectivities via a new approach, which combines asymmetric hydrogenation of β-ketosulfones and Mitsunobu amination reaction of the corresponding β- hydroxysulfones with a significant high control of the stereochemistry.