Strained silacycles in organic synthesis: a new reagent for the enantioselective allylation of aldehydes

A new reagent for the enantioselective allylation of aliphatic aldehydes has been developed. The reagent is easily prepared in a single step from commercially available materials and may be stored without significant decomposition. The reactivity of the reagent is attributed to strain-release Lewis acidity.     

Silicon tetrachloride in organic synthesis: new applications for the vinylogous aldol reaction

This paper describes a novel and efficient methodology for vinylogous aldol reactions based on SiCl₄ catalysis. According to the nucleophilicity Mayr's scale, vinylogous aldol reaction of Chan's diene proved to be effective by using catalytic amount of SiCl₄, without any other promoter. On the contrary, the SiCl₄/Lewis base system has been conveniently exploited for the efficient and selective vinylogous reaction of less nucleophilic Danishefsky's diene and 2-trimethylsilyloxyfuran (TMSOF). Indeed, a number of Lewis bases, such as sulfoxides, formamides and phosphoramides have been successfully used as SiCl₄ promoters. TMSOF and silyloxydienes, resulting from 2,2,6-trimethyl-[1,3]-dioxin-4-one derivatives, required stoichiometric amount of SiCl₄, while vinylogous aldol reaction of Chan's and Danishefsky's dienes took satisfactorily place in the presence of catalytic or sub-stoichiometric amount of catalyst.     

Progress toward the total synthesis of saudin: development of a tandem Stille-oxa-electrocyclization reaction

[reaction: see text] A diastereoselective tandem Stille-oxa-electrocyclization reaction provides access to the core of the diterpenoid natural product saudin. Additionally, this new reaction sequence was extended to the convergent preparation of related polycyclic pyran systems.     

Thiol-mediated tandem Michael-aldol reaction: a convenient method for the synthesis of fused cyclopentenones

A simple, convenient, one-pot synthetic approach towards substituted cyclopentenone derivatives via thiol-mediated tandem Michael-aldol reaction followed by acid-catalyzed thiol elimination and isomerization of 3-(2-formyl-3,4-dihydronapthalene 1-yl)-acrylic acid esters has been developed.     

Heterobimetallic alkyne complexes in organic synthesis: An asymmetric variant of the Pauson-Khand reaction

The use of heterobimetallic alkyne complexes for the synthesis of cyclopentenones is described. The inherent chirality of the complexes has been used to effect high levels of stereocontrol in transformations giving optically enriched organic end products.     

A rapid synthesis of the biotin core through a tandem Michael reaction

A biotin core has been assembled in a short and efficient sequence utilizing a tandem intramolecular Michael reaction/fragmentation/Michael reaction from vinyl sulfoxide and sulfone alcohols (12 and 13).     

Ultrasound in organic synthesis 9 further results for the bouveault reaction

The Bouveault reaction under ultrasonic irradiation can readily be effected from various amides and the effect of the solvent was studied. In the case of diethylether, results are strongly dependent on the wave frequency.     

Pummerer反应在有机合成中的新进展

综述了Pummerer反应的机理、类型及其在有机合成和不对称合成中的新进展。     

One-pot synthesis of quinoline-based tetracycles by a tandem three-component reaction

A practical one-pot synthetic strategy for the efficient synthesis of a range of structurally interesting and bioactive quinoline-based tetracycles has been developed. A key step in the synthesis is a tandem three-component reaction of heteroaromatic amine, methyl 2-formylbenzoate and (t)butyl isonitrile, followed by TFA-mediated lactamization via intramolecular aminolysis of an adjacent ester. Results related to a kinase-panel screening for several selected compounds are also discussed in this article.     

Organocatalytic highly enantioselective tandem Michael-Knoevenagel reaction for the synthesis of substituted thiochromanes

Enantioenriched tetrasubstituted thiochromanes have been synthesized using a tandem Michael addition-Knoevenagel reaction between 2-mercaptobenzaldehydes and benzylidenemalonates with a 9-epi-aminoquinine thiourea derivative as the catalyst. Steric and electron effects were found to affect profoundly the enantioselectivity and diastereoselectivity of the reaction.     

A one-pot asymmetric organocatalytic tandem reaction for the synthesis of oxazine derivatives

An easy one-pot tandem reaction catalyzed by a chiral secondary amine for the synthesis of optically active oxazine derivatives has been performed and the corresponding substituted benzo[d]pyrido[2,1-b][1,3]oxazine derivatives were afforded in generally high yields (up to 99%) and excellent enantioselectivities (up to >99%).     

Nucleophilic partners in the tandem conjugate addition-Dieckmann condensation reaction: 1. synthesis of 1,2,3-trisubstituted naphthalenes

The scope and limitations of the tandem conjugate addition-Dieckmann condensation for the construction of 1,2,3-trisubstituted naphthalenes is defined. Viable nucleophilic partners in this methodology include organocuprates, active methylenes, and a variety of heteroatom initiators.     

A new tandem reaction of benzyne: one-pot synthesis of aryl amines containing anthracene

[reaction: see text] The reaction of benzyne with N-substituted imidazoles affords a novel way to prepare arylamines containing anthracene under very mild conditions. This transformation is assumed to proceed via a tandem reaction involving a Diels-Alder reaction and an intermolecular nucleophilic coupling reaction.     

Nitriles in organic synthesis: The reaction of trichloroacetonitrile with active methylene reagents

The reaction of trichloroacetonitrile with active methylene reagents such as acetylacetone, benzoylacetone, cyanoacetamide and cyanoacethydrazide is reported. A new simple route for the synthesis of polysubstituted phenols, pyrazoles and pyrroles is also described.

---

Nitrile bei organischen Synthesen: Die Reaktion von Trichloracetonitril mit aktiven Methylen-Reagentien

Zusammenfassung Es wird über die Reaktionen von Trichloracetonitril mit aktiven Methylen-Reagentien wie Acetylaceton, Benzoylaceton, Cyanacetamid und Cyanacethydrazid berichtet. Ein neuer einfacher Weg für die Synthese polysubstituierter Phenole, Pyrazole und Pyrrole wird beschrieben.

     

Iodine-catalyzed tandem oxidative coupling reaction: A one-pot strategy for the synthesis of new coumarin-fused pyrroles

The simple and facile strategy for the synthesis of 2,3-disubstituted-chromeno[4,3-b]pyrrole-4(1H)-ones has been established. This method describes the Kornblum oxidation reaction of acetophenones, followed by the Knoevenagle treatment of the resulted (het)arylglyoxals with active methylene compounds and consequently iodine-activated Michael type reaction with 4-amino coumarin in a one-pot manner to afford disubstituted chromeno[4,3-b]pyrrole-4(1H)-one derivatives.