A Convenient Route to Norpyrenophorin

A norpyrenophorin precursor has been achieved by a three-step synthesis in good yield.     

A Convenient Formal [4+2] Heterocylization Route to Bis(triflyl)tetrahydroquinolines

We report the sustainable and efficient synthesis of a new type of quinoline derivatives bearing one or two SO₂CF₃ groups. The protocol is metal-, catalyst- and irradiation-free, involves the use of readily available and stable precursors, and avoids the formation of side products. Also, the mild conditions of the process allow the tolerance of a wide range of functional groups.     

A Convenient Route to Mixed Pnictogenylboranes

We report on the synthesis and characterization of mixed pnictogenylboranes. The substitution of the Lewis base SMe₂ in (OC)₅W–PH₂BH₂–SMe₂ ( 2 ) by different pnictogenylboranes ER₂BH₂–LB (E=P, As, Sb) leads to the Lewis acid/base stabilized butane analogue (OC)₅W–PH₂BH₂ER₂BH₂–LB ( 3 a , b : E=P; R=H, SiMe₃; LB=NMe₃; 4 a , b : E=As; R=H, SiMe₃; LB=NMe₃; 5 : E=Sb; R=SiMe₃; LB=NHC^Me). All of these compounds were characterized by single‐crystal X‐ray structure analysis, mass spectrometry, NMR, and IR spectroscopy. In addition, the very unstable phosphanylborane chain PH₂BH₂PH₂BH₂–NMe₃ ( 1 ) was synthesized. DFT calculations provide insight into the thermodynamics of these reactions.     

A Convenient Route to Substituted Thiocarbamides

A varicty of substituted thioureas result from thiuram disufides by a simple reaction with different amines.     

Bis(difluoromethyl)trimethylsilicate Anion: A Key Intermediate in Nucleophilic Difluoromethylation of Enolizable Ketones with Me3SiCF2H

A pentacoordinate bis(difluoromethyl)silicate anion, [Me₃Si(CF₂H)₂]^?, is observed for the first time by the activation of Me₃SiCF₂H with a nucleophilic alkali‐metal salt and 18‐crown‐6. Further study on its reactivity by tuning the countercation effect led to the discovery and development of an efficient, catalytic nucleophilic difluoromethylation of enolizable ketones with Me₃SiCF₂H by using a combination of CsF and 18‐crown‐6 as the initiation system. Mechanistic investigations demonstrate that [(18‐crown‐6)Cs]⁺[Me₃Si(CF₂H)₂]^? is a key intermediate in this catalytic reaction.     

Long‐Lived Trifluoromethanide Anion: A Key Intermediate in Nucleophilic Trifluoromethylations

The trifluoromethanide anion is the postulated key intermediate in nucleophilic trifluoromethylation reactions. However, for more than six decades, the trifluoromethanide anion was widely believed to exist only as a short‐lived transient species in the condensed phase. It has now been prepared in bulk for the first time in THF solution. The trifluoromethanide anion with the [K(18‐crown‐6)]⁺ cation was unequivocally characterized by low‐temperature ¹⁹F and ¹³C NMR spectroscopy. Its intermediacy in nucleophilic trifluoromethylation reactions was directly evident by its reaction chemistry with various electrophilic substrates. Variable‐temperature NMR spectroscopy, along with quantum mechanical calculations, support the persistence of the trifluoromethanide anion.     

4,5‐Dihydro‐1,2,3‐oxadiazole: A Very Elusive Key Intermediate in Various Important Chemical Transformations

4,5‐Dihydro‐1,2,3‐oxadiazoles are postulated to be key intermediates in the industrial synthesis of ketones from alkenes, in the alkylation of DNA in vivo, and in the decomposition of N‐nitrosoureas; they are also a subject of great interest for theoretical chemists. In the presented report, the formation of 4,5‐dihydro‐1,2,3‐oxadiazole and the subsequent decay into secondary products have been studied by NMR monitoring analysis. The elusive properties evading characterization have now been confirmed by ¹H, ¹³C, and ¹⁵N NMR spectroscopy, and relevant 2D experiments at very low temperatures. Our experiments with suitably substituted N‐nitrosoureas using thallium(I) alkoxides as bases under apolar conditions answer important questions on the existence and the secondary products of 4,5‐dihydro‐1,2,3‐oxadiazole.     

A Convenient Route to Condensed-Ring Aromatic Acetylenes

Palladium catalysed coupling of aryl halides with 3-methylbut-1-yn-3-ol and a subsequent base-induced retro-Favorsky reaction gave the corresponding ethynyl aromatics in good to excellent yields.     

Transfer of Electrophilic NH Using Convenient Sources of Ammonia: Direct Synthesis of NH Sulfoximines from Sulfoxides

A new system for NH transfer is developed for the preparation of sulfoximines, which are emerging as valuable motifs for drug discovery. The protocol employs readily available sources of nitrogen without the requirement for either preactivation or for metal catalysts. Mixing ammonium salts with diacetoxyiodobenzene directly converts sulfoxides into sulfoximines. This report describes the first example of using of ammonia sources with diacetoxyiodobenzene to generate an electrophilic nitrogen center. Control and mechanistic studies suggest a short‐lived electrophilic intermediate, which is likely to be PhINH or PhIN⁺.     

Solution Phase Reactivity of Dibenzo[c,e][1,2]azaborinine: Activation and Insertion into Si-E Single Bonds (E=H,OSi(CH3)3, F,Cl) by a BN-Aryne

The boron-nitrogen analogue of ortho-benzyne, 1,2-azaborinine, is a reactive intermediate that features a formal boron-nitrogen triple bond. We here show by combining experimental and computational techniques that the Lewis acidity of the boron center of dibenzo[c,e][1,2]azaborinine allows interaction with the silicon containing single bonds Si−E through the silicon bonding partner E (E=F, Cl, OR, H). The binding to boron activates the Si−E bonds for subsequent insertion reaction. This shows that the BN-aryne is a ferocious species that even can activate and insert into the very strong Si−F bond.     

A Convenient Route to 5,6-Diphenyl-5,6-dihydro-uracils

Diphenylcyclopropenone(1) reacts with a variety of thiopseudoureas to eventually afford dihydrouracils     

Discovery of the New Metastable HONF. Radical

The new radical HONF has been detected in the gas phase by neutralization–reionization mass spectrometry (NRMS). The radical has been identified and directly characterized as a gaseous isolated species, having a lifetime of at least 1 μs and a linear cis–trans structure of H‐O‐N‐F connectivity. Detection of this molecule, which is highly unstable towards the dissociation into HF and NO and kinetically sufficiently stable to be observed, represents an advance in the search for high‐energy species.     

A Convenient Route to New 4,5-Dimercapto-1,3-thiazole Derivatives

A series of 2-X-4-tosyl-5-chloro-1,3-thiazoles (X = OH, OAlk, SH, SAlk, NH₂, NHAlk, NAlk₂, NHAr, etc.) were prepared from accessible 1-tosyl-2,2-dichloroethenyl isothiocyanate. Only some of these compounds containing a moderately labile hydrogen atom peculiarly react with thiophenols in the presence of triethylamine to give 4,5-di(arylthio)-2-(hydroxy- or arylamino)-1,3-thiazoles, which are difficult to prepare by other routes. It is quite possible that, in the course of nucleophilic substitution of the chlorine atom and tosyl residue by the corresponding arylthio groups, a significant role is played by nonaromatic tautomeric forms of functionally 2-substituted 1,3-thiazoles formed by proton transfer to positions 3 and 5 of the heteroring.     

Hydrostannylation of Red Phosphorus: A Convenient Route to Monophosphines

The preparation of valuable and industrially relevant organophosphorus compounds currently depends on indirect multistep procedures involving difficult-to-handle white phosphorus as a common P atom source. Herein, we report a practical and versatile method for the synthesis of a variety of monophosphorus compounds directly from the bench-stable allotrope red phosphorus (P_red). The relatively inert P_red was productively functionalised by using the cheap and readily available radical reagent tri-n-butyltin hydride, and subsequent treatment with electrophiles yields useful P₁ compounds. Remarkably, these transformations require only modest inert-atmosphere techniques and use only reagents that are inexpensive and commercially available, making this a convenient and practical methodology accessible in most laboratory settings.     

Convenient Route to Thiocarbonates from Alcohols,Thiols, and Triphosgene

An efficient and simple one-pot, three-component procedure has been introduced for the preparation of various thiocarbonates from thiols, alcohols, and triphosgene in dichloromethane.