A study of η-allyl(η-cyclopentadienyl)- dicarbonylmanganese salts

New substituted η³-allyl(η⁵-cyclopentadienyl)dicarbonylmanganese cations have been prepared as their tetrafluoroborates. They readily add a wide range of nucleophiles yielding η²-alkene(η⁵-cyclopentadienyl)dicarbonylmanganese complexes. Of the latter, in general only those involving terminal alkenes are sufficiently stable to permit ready isolation; otherwise metal-free alkenes are obtained. Regioselectivity in these additions depends on the nucleophile.     

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)-alkenyl)iodonium tetrafluoroborates with tetrabutyl-ammonium halides: retention of configuration

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)alkenyl)-phenyliodonium tetrafluoroborates 1 with tetrabutylammonium halides (Cl, Br, and I) proceed with exclusive retention of configuration at room temperature and afford (Z)-β-(phenylsulfonyl)vinyl halides 2 in high yields.     

Generation of Sulfonyl Radicals from Aryldiazonium Tetrafluoroborates and Sulfur Dioxide: The Synthesis of 3‐Sulfonated Coumarins

A catalyst‐free approach for the generation of sulfonyl radicals from aryldiazonium tetrafluoroborates in the presence of DABCO?(SO₂)₂ is realized. The combination of aryldiazonium tetrafluoroborates, DABCO?(SO₂)₂, and aryl propiolates affords 3‐sulfonated coumarins in good to excellent yields. This tandem reaction process involves radical addition, spirocyclization, and 1,2‐migration of esters. Additionally, the in situ diazotization of a number of anilines allows the directional synthesis of desired 3‐sulfonated coumarins in a one‐pot, two‐step process.     

Adducts of thianthrene- and phenoxathiin cation radical tetrafluoroborates to 1-alkynes. Structures and formation of 1-(5-thianthreniumyl)- and 1-(10-phenoxathiiniumyl)alkynes on alumina leading to alpha-ketoylides and alpha-ketols

[structure: see text] Thianthrene cation radical tetrafluoroborate (Th*+ BF4(-)) added to the terminal alkynes 1-pentyne, 1-hexyne, 1-heptyne, 1-octyne, 1-nonyne, and 1-decyne to form trans-1,2-bis(5-thianthreniumyl)alkene tetrafluoroborates (1-6). Similarly, addition of phenoxathiin cation radical tetrafluoroborate (PO*+ BF4(-)) to the same alkynes gave 1,2-bis(10-phenoxathiiniumyl)alkene tetrafluoroborates (7-12). The trans configuration of two of the adducts (1 and 4) was shown with X-ray crystallography. When solutions of 1-6 in chloroform were stirred with activated alumina, cis elimination of a proton and thianthrene (Th) occurred with the formation of 1-(5-thianthreniumyl)alkyne tetrafluoroborates (1a-6a). Similar treatment of 8-12 caused elimination of a proton and phenoxathiin (PO) with formation of 1-(10-phenoxathiiniumyl)alkene tetrafluoroborates (8a-12a). Stirring of 1a-6a with alumina for short periods of time caused their conversion into 5-[(alpha-keto)alkyl]thianthrenium ylides (1b-6b) and alpha-ketols, RC(O)CH2OH (1c-6c).     

Stereoselective synthesis of fluoroalkenes via (Z)-2-fluoroalkenyliodonium salts

Stereoselective synthesis of fluoroalkenes is described. (Z)-2-Fluoro-1-alkenyl(phenyl)iodonium tetrafluoroborates (1) were synthesized stereoselectively in good yields by Michael-type addition of HF to 1-alkynyl(phenyl)iodonium tetrafluoroborates (2) with a commercially available HF reagent, hydrofluoric acid or Et₃N-3HF. Pd-catalyzed cross-coupling reactions using 1 gave (Z)-2-fluoro-1-alkene derivatives in moderate yields. The treatment of 1 with KI in the presence of a catalytic amount of CuI gave (Z)-2-fluoro-1-iodo-1-alkenes (3). Pd-catalyzed cross-coupling reactions of 3 gave better results than that of 1, and a variety of (Z)-2-fluoro-1-alkene derivatives were synthesized in good yields.     

Catalyst-free Mannich-type reaction of 1-(N-acylamino)alkyltriphenylphosphonium salts with silyl enolates

A catalyst-free reaction of 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates with silyl enolates was developed to prepare β-amino carbonyl compounds. The reported method is a useful approach for the preparation of N-protected β-amino esters as well as N-protected β-amino ketones. The starting 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates are readily available from N-protected α-amino acids. Therefore, the presented approach can be considered a new method for the α-homologation of N-protected α-amino acids to prepare β-amino acid derivatives.     

(1-(Dimethylamino)-2-(diphenylphosphino)ethane)(eta(3)-1-arylallyl)palladium Tetrafluoroborates. Preparation, Isomeric Equilibria, and Correlations of NMR Chemical Shifts with Hammett Substituent Constants

13C NMR differences of chemical shifts (delta(X) - delta(H)) of allyl carbon atoms in a series of trans-(1-(diphenylphosphino)-2-(dimethylamino)ethane)(eta(3)-1-arylallyl)palladium tetrafluoroborates, X ranging from NO(2) to OMe, correlate very well with sigma Hammett constants for C-1 and with sigma(+) for C-3, this carbon atom being in a trans relationship with the positively charged nitrogen atom.     

Visible‐Light Photoredox‐Catalyzed and Copper‐Promoted Trifluoromethoxylation of Arenediazonium Tetrafluoroborates

We report the development of photoredox‐catalyzed and copper‐promoted trifluoromethoxylation of arenediazonium tetrafluoroborates, with trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxylation reagent. This new method takes advantage of visible‐light photoredox catalysis to generate the aryl radical under mild conditions, combined with copper‐promoted selective trifluoromethoxylation. The reaction is scalable, tolerates a wide range of functional groups, and proceeds regioselectively under mild reaction conditions. Furthermore, mechanistic studies suggested that a Cs[Cu(OCF₃)₂] intermediate might be generated during the reaction.     

Synthesis and Some Reactions of 1-α-Cyanoalkyl(aralkyl)-2-pyrazolines

1-α-Cyanoalkyl(aralkyl)-2-pyrazolines were obtained by the reaction of 1-alkylidene(arylidene)-2-pyrazolinium tetrafluoroborates with metal cyanides. Reduction of the products led to substituted β-aminoalkyl-2-pyrazolines. Hydrolysis of the nitrile groups gave the corresponding substituted acetamides. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, 10, 1558–1565, October 2005.     

A novel route to bicyclic iron tricarbonyl complexes involving π-allyl and σ-components

Nucleophilic attack of CN⁻ on bicyclo[3.2.1]octadienyl-, bicyclo[3.2.2]- nonadienyl-, and 6,7-benzobicyclo[3.2.2]nonadienyliron tricarbonyl tetrafluoroborates, results in mixed-type complexes containing both σ and π-allyl bonds. The cyano group in the products is located exo to the bicyclic ring.In contrast, the three cations react smoothly with I⁻; carbon monoxide is displaced to give iron complexes containing covalently-bound halogen.     

Synthese nouvelle et rapide d'alkylseleno et alkyltelluroarenes au moyen d'ethers-couronnes

A phase transfer catalytic synthesis of alkylseleno and alkyltelluro-arenes is describe from arenediazonium tetrafluoroborates and dialkyldichalcogenides.     

Synthesis and crystal structure analysis of a 6aλ4-thia-1,2,3,4,6-pentaazapentalene

6aλ⁴-Thia-1,2,3,4,6-pentaazapentalenes 3 are conveniently prepared by reacting 5-imino-Δ³-1,2,4-thiadi-azolines 2 with aromatic diazonium tetrafluoroborates in the presence of pyridine. The first crystal structure analysis of this class of compounds 3g is described and shows properties characteristic of a thiapentalene structure; i.e. long N-S-N bonds (1.85 and 1.975 Å) in a nearly linear arrangement (164°) and comprising a heterobicycle which is strictly planar.     

Copper‐Mediated Di‐ and Monofluoromethanesulfonylation of Arenediazonium Tetrafluoroborates: Probing the Fluorine Effect

A copper‐mediated di‐ and monofluoromethanesulfonylation of arenediazonium tetrafluoroborates using di‐ and monofluoromethanesulfinate reagents provides aryl difluoromethyl (or monofluoromethyl) sulfones in good yields. It was found that the relative reactivity of these sodium fluoroalkanesulfinates in the present reactions decreases in the following order: CH₂FSO₂Na > CF₂HSO₂Na > CF₃SO₂Na.     

Synthesis of 2-alkyl-1,2,4-benzotriazin-3(2h)-ones and 2-alkyl-1,4-dihydro-1,2,4-benzotriazin-3(2h)-ones

A preparative method for the synthesis of 2-alkyl-1,2,4-benzotriazin-3(2H)-ones 3 was developed. The method involves treatment with sodium cyanate of 2-alkylbenzotetrazinium tetrafluoroborates, which exist in solutions in equilibrium with o-(alkylazo)aryldiazonium tetrafluoroborates. Reduction of compounds 3 with zinc in acetic acid afforded 2-alkyl-1,4-dihydro-1,2,4-benzotriazin-3(2H)-ones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 346–349, February, 2006.     

Assembly of 3-sulfonated 2H-pyrrol-2-ones through the insertion of sulfur dioxide with allenoic amides

Generation of 3-sulfonated 2H-pyrrol-2-ones through a three-component reaction of allenoic amides, sulfur dioxide, and aryldiazonium tetrafluoroborates under metal-free conditions is achieved. This transformation proceeds under mild conditions without the addition of catalysts or additives, giving rise to 3-sulfonated 2H-pyrrol-2-ones in moderate to good yields. Good functional group compatibility is observed. A plausible mechanism is proposed, which is initiated by aryl radicals formed in situ from aryldiazonium tetrafluoroborates and DABCO·(SO₂)₂. Additionally, excellent chemoselectivity and regioselectivity are presented in this transformation.     

A new convenient synthesis of N-acyl-2-(dimethoxyphosphoryl)glycinates

Easily accessible N-acyl-2-triphenylphosphonioglycinate tetrafluoroborates react smoothly with trimethylphosphite in the presence of methyltriphenylphosphonium iodide to give N-acyl-2-(dimethoxyphosphoryl)glycinates in good or very good yields. The dimethoxyphosphorylglycinates may be isolated by column chromatography, or used directly for the Wadsworth-Emmons synthesis of α,β-dehydro-α-amino acids in a one-pot procedure without purification.     

Metal‐Free Aminosulfonylation of Aryldiazonium Tetrafluoroborates with DABCO⋅(SO2)2 and Hydrazines

The coupling of aryldiazonium tetrafluoroborates, DABCO?(SO₂)₂, and hydrazines under metal‐free conditions leads to the formation of aryl N‐aminosulfonamides. The reaction proceeds smoothly at room temperature and shows broad functional‐group tolerance. A radical process is proposed for this transformation.     

Novel ionic liquids—Imidazolium salts with a difluoromethylene fragment directly bonded to the nitrogen atom

Alkylation of N-(1,1,2,2-tetrafluoroethyl)imidazole (1) by alkyl iodides and metathesis resulting in corresponding tetrafluoroborates and bis(trifluoromethanesulfonyl)amides led to the formation of new type stable ambient temperature ionic liquids 3 and 4 with a difluoromethylene fragment directly bonded to the nitrogen atom.     

Assembly of 3-sulfonated 2H-pyrrol-2-ones through the insertion of sulfur dioxide with allenoic amides

Generation of 3-sulfonated 2H-pyrrol-2-ones through a three-component reaction of allenoic amides, sulfur dioxide, and aryldiazonium tetrafluoroborates under metal-free conditions is achieved. This transformation proceeds under mild conditions without the addition of catalysts or additives, giving rise to 3-sulfonated 2H-pyrrol-2-ones in moderate to good yields. Good functional group compatibility is observed. A plausible mechanism is proposed, which is initiated by aryl radicals formed in situ from aryldiazonium tetrafluoroborates and DABCO·(SO₂)₂. Additionally, excellent chemoselectivity and regioselectivity are presented in this transformation.     

Fluoroazoles. II. Synthesis and 1H and 19F Nmr spectra of 2-, 4-, and 5-Fluoro-1-methylimidazole

The three possible ring-monofluorinated N-methylimidazoles have been prepared by photochemical irradiation of the corresponding diazonium tetrafluoroborates. 5-Fluoro-1-methyl-imidazole was also obtained by methylation of 1-acetyl-4-fluoroimidazole. The ¹H and ¹⁹F nmr spectra of these N-methylated fluoroazoles are compared, and the predominance of one tautomeric form in 4(5)-fluoroimidazole is discussed.