Facile [3,3]-sigmatropic rearrangement in the reaction of α-chloroperfluorostyrene with allyl alcohol

The reaction of -chloroperfluorostyrene (1) with allyl alcohol in the presence of KOH at 45–50°C leads to a mixture of the allyl 2-pentafluorophenyl-2-chloro-4-pentenoate (2) and the product of the addition of the starting reagents (3). Ester2 is formed as the result of a mild [3,3]-sigmatropic rearrangement of the reaction intermediate.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1925–1926, August, 1992.     

A convenient synthesis of 2-aryl substituted benzo[f] [1,2,4]triazolo[1,5-a]azepine derivatives

A convenient synthetic pathway to 2-aryl-5,6-dihydro-4H-benzo[f][1,2,4]triazolo[1,5-α]azepine derivatives 7 was developed. The synthesis was based on the cycloaddition of the 1,2,3,4-tetrahydronaphthalene a-acetoxy azo compounds 3 with Ar-CN in the presence of AlCl3 and the consecutive ring enlargement.     

Recent development of ortho-C–H functionalization of aryl sulfoxides through [3,3] sigmatropic rearrangement

Sulfoxide-promoted ortho-C–H functionalization reactions of aromatic compounds have emerged as powerful tools for organic synthesis. Among them, [3,3] sigmatropic rearrangement induced by interrupted Pummerer reaction or electrophilic activation of sulfoxides has proved to be a fruitful strategy due to its versatility and high reaction efficiency. This digest paper mainly focuses on recent progress on C–H functionalization reactions of aryl sulfoxides via [3,3] sigmatropic rearrangement of sulfonium-tethered intermediates.     

New sigmatropic sequences based on the [2,3]-wittig rearrangement of the bis-allylic ether system : A general approach to regiocontrolled c—c bond formation of allylic moieties leading to unsaturated carbonyl compounds

Four new sigmatropic sequences triggered by the regiocontrolled [2,3]-Wittig rearrangement of unsymmetrical bis-allylic ethers (1) to the l,5-dien-3-ols (2) arc described, which provide unique, regiocontrolled methods for the synthesis of a wide variety of unsaturated carbonyl compounds possessing interesting molecular frameworks. The newly developed sequences include the [2,3]-Wittig-Claisen, the tandem [2,3]-Wittig-oxy-Cope, the tandem oxy-Cope-Claisen, and the tandem oxy-Cope-Cope sequences.     

Copper-catalyzed direct oxyphosphorylation of alkynes with H-phosphine oxides and dioxygen: A convenient approach to β-ketophosphine oxides

A simple and facile copper-catalyzed synthesis of β-ketophosphine oxides via direct oxyphosphorylation of alkynes with H-phosphine oxides and dioxygen has been developed under mild conditions without any base or cocatalyst. A radical reaction pathway for the formation of β-ketophosphine oxides is proposed. An ¹⁸O labeling experiment suggested that the carbonyl oxygen atom of β-ketophosphine oxides originated from dioxygen.     

A new and convenient approach for the preparation of β-cyanoethyl protected trinucleotide phosphoramidites

Herein we report a convenient approach for the preparation of fully protected trinucleotide synthons to be used for the synthesis of gene libraries. The trinucleotide synthons bear β-cyanoethyl groups at the phosphate residues, and thus can be used in standard oligonucleotide synthesis without additional steps for deprotection and work-up.     

Towards a synthesis of (±)modhephene via cascade rearrangement: Synthesis and rearrangement of dispiro[3.0.4.2]undecanes to [3.3.3]propellanes

The dispiro [3.0.4.2] undecanes 2 and 6 undergo cascade rearrangements yielding the [3.3.3]propellanes 3 and 7, respectively. The rearrangement of 6 proceeds regiospecifically and renders 9 a promising candidate for a direct conversion to (±)modhephene 10.     

A New Short Synthesis of 3, 3′-Methylene Bis[Coumarins] and 3,3-Methylene Bis[2-Diethylaminoquinolines]

Hitherto unknown six symmetrically and unsymmetrically substituted methylene bis(coumarins) and two methylene bis(quinolines) are synthesised by using 1:2 complex of N, N, N', N'-tetraethyl glutaramide with POCl₃ and its condensation with substituted salicyl-aldehydes and o-formyl acetanilides.     

A silica-gel accelerated [4 + 2] cycloaddition-based biomimetic approach towards the first total synthesis of magterpenoid C

The first total synthesis of magterpenoid C has been realized via a silica gel accelerated biomimetic Diels-Alder reaction between β-myrcene and randaiol derived quinone. However, application of similar strategy towards magterpenoid B via a protective Diels-Alder reaction failed to deliver the natural product.     

The unusual stability of [NpO2Cl4]2−: Synthesis and characterisation of [NpO2(DPPMO2)2Cl]2[NpO2Cl4] and [Ph3PNH2]2[NpO2Cl4]

The [NpO₂(DPPMO₂)₂Cl][NpO₂Cl₄] complex (where DPPMO₂ = bis(diphenylphosphino)methanedioxide) contains the linear neptunyl group, {NpO₂}²⁺, with two bidentate P=O donor ligands. Coordinating anion Cl^? fills the fifth equatorial coordination site yielding a complex of general formula [NpO₂(DPPMO₂)₂X]₂[Y] (1) (where X = Cl^? and Y = [NpO₂Cl₄]^2?. Reaction between our newly prepared neptunium starting material [NpO₂Cl₂(thf)]_n and phosphinimine ligand produced crystals of [Ph₃PNH₂]₂[NpO₂Cl₄] (2). Compounds 1 and 2 have been structurally characterised.     

Rhodium promoted intramolecular [4 + 2] cycloaddition of 2-azidodiene with alkyne: A transition metal catalysis approach to challenging fused bicyclic vinyl azide

Although vinyl azide is an important class of functional group that possesses diverse reactivities and is a convenient synthon for N-heterocycles, cyclic vinyl azide remains underdeveloped due to difficult preparation. This work discloses a rhodium catalyzed intramolecular [4?+?2] cycloaddition reaction that can afford challenging fused bicyclic vinyl azides efficiently in ambient conditions and paves a facile route for the research in the chemistry of cyclic vinyl azides.     

The first example of [2+2] cycloaddition of Me4Ge2 to multiple bonds. The synthesis of Δ1,7-2,2,6,6,8,8,9,9-octa-methyl-4-thia-8,9-digermabicyclo[5.2.0]Nonene

The first example of a [2+2] cycloaddition reaction of Me₄Ge₂ with acetylene is described. A new derivative of 1,2-digermacyclobutene, namely Δ^1,7-2,2,6,6,8,8,9,9-octamethyl-4-thia-8,9-digermabicyclo[5.2.0]nonene, is prepared.     

N-Benzyloxycarbonyl-2,2,2-trifluoroacetimidoyl chloride—A convenient reagent for the synthesis of 2-trifluoromethyl-4H-pyrido[1,2-a][1,3,5]triazin-4-one

N-Benzyloxycarbonyl-2,2,2-trifluoroacetimidoyl chloride reacted with pyridin-2-amine derivatives to form substituted 2-trifluoromethyl-4H-pyrido[1,2-a][1,3,5]triazin-4-ones.     

Chemo- and stereoselective six-membered oxonium ylide formation–[2,3]-sigmatropic rearrangement of 2-diazo-3-ketoesters with dirhodium(II) catalyst and its application to the synthesis of (+)-tanikolide

Dirhodium(II)-catalyzed oxonium ylide formation–[2,3]-sigmatropic rearrangement of 6-allyloxy-2-diazo-3-ketoesters possessing a C-6 substituent is described. The reaction of 6-alkyl- or 6-aryl-substituted 6-allyloxy-2-diazo-3-ketoesters with a catalytic amount of Rh₂(S-PTTL)₄ proceeded in a chemoselective and stereoselective manner to provide 6-substituted 2-allyl-3-oxotetrahydropyran-2-carboxylates in good yields and with high diastereoselectivities. To demonstrate the utility of this sequential reaction, we conducted the total synthesis of (+)-tanikolide, in which the construction of the δ-lactone skeleton was achieved by employing a 2-iodobenzamide-catalyzed oxidative cleavage of tetrahydropyran-2-methanol.     

A convenient synthesis of pyrrolo[2,3-b]pyridines and pyrido[2′,3′:5,4]pyrrolo[2,3-d]pyrimidines

2-Chloro-6-ethoxy-4-phenylpyridine-3,5-dicarbonitrile was taken as versatile building block that allows the synthesis of 1H-pyrrolo[2,3-b]pyridine, thieno[2,3-b]pyridine and pyrido[2′,3′:5,4]pyrrolo[2,3-b]pyrimidine systems. Some of the synthesized compounds were screened as antibacterial agents.     

Oxidation of β-Hydroxynitrosamines to β-Ketonitrosamines with KMnO4-Metal.SO4.XH2O in Non-Aqueous Media

The oxidation of β-hydroxynitrosamines to the corresponding β-ketonitrosamine is reported. The reactions carried out in benzene or dichloromethane using powdered KMnO₄-CuSO₄.5H₂O, or KMnO₄-MgSO₄.7H₂O. Work-up of the reaction and purification of the product requires only a filtration through magnesium sulfate and chromatography through a short Florisil column.     

Five-membered 2,3-dioxo heterocycles: XCVIII. [4 + 2]-cycloaddition of alkyl vinyl ethers to 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones. A new synthetic approach to heteroanalogs of 13(14→8)-abeo steroids

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones reacted with alkyl vinyl ethers according to the [4 + 2]-cycloaddition pattern with formation of substituted (1S*,16R*)- and (1R*,16R*)-16-alkoxy-14-aryl-3,15-dioxa-10-azatetracyclo[8.7.0.0^1,13.0^4,9]heptadeca-4,6,8,13-tetraene-2,11,12-triones. The structure of (1S*,16R*)-7-chloro-16-ethoxy-14-phenyl-3,15-dioxa-10-azatetracyclo[8.7.0.0^1,13.0^4,9]heptadeca-4,6,8,13-tetraene-2,11,12-trione was determined by X-ray analysis. A new synthetic approach was developed to heteroanalogs of 13(14→8)-abeo steroids, substituted 3,15-dioxa-10-azatetracyclo[8.7.0.0^1,13.0^4,9]heptadecanes.