Letters in Organic Chemistry - Volume 3, Issue 5, 2006

Efficient small-molecule organocatalysis of asymmetric acyl-transfer reactions is a young field only a decade old. This highlight article reviews successes in this area with a focus on readily prepared aminopyridine-derived chiral catalysts for the kinetic resolution of sec-alcohols and a range of other synthetically useful transformations.

Organocopper reagents are amongst the most important C-C bond forming tools available to organic chemists. Recent interest in these reagents has focused on further developing preparative methods, exploring the reactivity of functionalized cuprates and developing stereoselective transformations. This highlight briefly reviews the advances made in each of these areas over the last five years

The photochemical reaction of 1-phenyl-2-methyl-1-butanone with furan gave propiophenone via a Norrish Type II reaction. The same behavior was observed using 1-phenyl-2-methyl-1-pentanone. In this case, the product derived from a Norrish-Yang reaction was obtained. The photochemical reaction of 2- phenylpropiophenone with furan and 2-methylfuran gave the corresponding Paternò-Büchi adducts. 2- Methylfuran gave a Read More

We describe the formation of acrylamide from alanine containing peptides at 200°C without the assistance of an additional carbonyl compound. This experiment may mimic the formation of acrylamide during the baking of bread.

The reaction of 5-trifluoromethyl-3-aminopyrazole with 1,1,1-trihalo-4-alkoxy-3-alken-2-ones CX3C (O)C(R2) = C(R1)OR, [where R2 = H, Me; R1 = H, alkyl, aryl, OEt and R = alkyl] both in the presence of environmentally benign microwave induced techniques and by the conventional method furnished eleven regiospecific halomethylated pyrazolo[1,5-a]pyrimidines. 1H- and 13C-NMR spectroscopy established that the 7-hydrox Read More

A series of novel chiral di-imidazolium tweezers were synthesized from L-alanine and L-phenylalanine. These compounds featured two open arms and multipoint binding sites. UV spectroscopic titration experiments showed these chiral di-imidazolium receptors exhibited excellent enantioselective recognition toward L- and D-amino acid derivatives in water or acetonitrile.

New types of ribosyl-diazepanone derivatives of nucleoside antibiotic liposidomycins, 12a and 12b, have been synthesised. The ribosyl 7-membered heterocycles were formed by reductive amination of the α-ribosylamino acid 9 derived from D-ribose and the amino aldehydes 10a or 10b, followed by a peptidic coupling reaction.

Palladium(0)-catalyzed annulation of N-substituted-2-aminophenols with propargylic methyl carbonates afforded the corresponding 3,4-dihydro-2-alkylidene- and 3,4-dihydro-3-alkylidene-2H-benzo[b] [1,4]oxazines; a judicious choice of the substituent at nitrogen allowed the preparation of one of the regioisomers.

Green, mild and efficient electrophilic substitution reactions of indoles with various aldehydes were carried out using solid superacid SO4 2-/TiO2 as recyclable catalyst, which afforded the corresponding bis(indolyl)methanes in excellent yields.

Reduction of 4-aza- and 5-azaphthalimides with Zn dust in acetic acid resulted in two distinct outcomes: i) in the 4-aza series, the reduction process stopped at the stage of 3-hydroxy-4-azaisoindolin-1- ones (isolated in 69-90% yield), presumably, stabilized by an intramolecular hydrogen bond; more forcing condition (110°C, 2 days) are required to obtain 4-azaisoindolin-1-ones; ii) in the 5-aza series, even at low temperatures (∼ Read More

An efficient method for the diastereoselective synthesis of various secondary amines through a titanium(IV) isopropoxide-mediated reductive amination reaction of ketones is reported. Thus, a series of different ketones and (R)-Phenylethylamine were involved leading to the expected products in moderate to excellent yields and importantly in diastereoselectivities up to 100% in one case.

Stereoselective synthesis of C1-C6 fragment of caribenolide I, a potent antitumour macrolide isolated from a marine dinoflagellate Amphidinium sp. is described. The key step relies on an asymmetric aldol reaction for control the absolute configurations of C2 and C3 stereogenic centers (caribenolide I numbering).

An efficient method for the synthesis of various secondary amines through a titanium(IV)- isopropoxide-mediated reductive amination reaction of ketones is reported. Thus, a series of different ketones and amines were involved leading to the expected products in moderate to excellent yields up to 98% in numerous cases. The mechanistic rationale of this reaction has been demonstrated through 1H and 13C NMR experiments Read More

Syntheses of 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)adenine (9) its 3'-deoxy derivative, 9-(2,3- dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (16), with the DAST treatment of the corresponding 3',5'- di-O-pivaloyladenosine (7) and its 3'-deoxy derivative 14 are described. The role of the pentofuranose ring stereochemistry of nucleosides 7 and 14 in the DAST fluorination is discussed. Stereoche Read More

The reaction of thioiminium salts derived from aromatic thioamides with lithium phenylacetylide exclusively gave S,N-acetals, whereas the reaction with lithium (trimethylsilyl)acetylide gave 1-amino-3- sulfenylallenes via [1,3]-rearrangement. The easiness of [1,3]-rearrangement was highly dependent on the substituents at the nitrogen atom. Chromatographic purification of the reaction mixture produced α,β- unsaturated ketones.

Palladium(II) chloride immobilized in ionic liquid [bmim][BF4] catalyzes the Michael reaction of indoles with α,β-unsaturated ketones to afford the corresponding β-indolylketones in excellent yields. The reaction proceeds at 0.1 mol% of Pd loading with high efficiency and great selectivity. The possible mechanism of the reaction was suggested.